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Heliothine moths (Lepidoptera: Heliothinae) include some of the world's most devastating pest species. Whereas the majority of nonpest heliothinae specialize on a single plant family, genus, or species, pest species are highly polyphagous, with populations often escalating in size as they move from one crop species to another. Here, we examine the current literature on heliothine host-selection behavior with the aim of providing a knowledge base for research scientists and pest managers. We review the host relations of pest heliothines, with a particular focus on Helicoverpa armigera (Hübner), the most economically damaging of all heliothine species. We then consider the important question of what constitutes a host plant in these moths, and some of the problems that arise when trying to determine host plant status from empirical studies on host use. The top six host plant families in the two main Australian pest species (H. armigera and Helicoverpa punctigera Wallengren) are the same and the top three (Asteraceae, Fabaceae, and Malvaceae) are ranked the same (in terms of the number of host species on which eggs or larvae have been identified), suggesting that these species may use similar cues to identify their hosts. In contrast, for the two key pest heliothines in the Americas, the Fabaceae contains ≈1/3 of hosts for both. For Helicoverpa zea (Boddie), the remaining hosts are more evenly distributed, with Solanaceae next, followed by Poaceae, Asteraceae, Malvaceae, and Rosaceae. For Heliothis virescens (F.), the next highest five families are Malvaceae, Asteraceae, Solanaceae, Convolvulaceae, and Scrophulariaceae. Again there is considerable overlap in host use at generic and even species level. H. armigera is the most widely distributed and recorded from 68 plant families worldwide, but only 14 families are recorded as a containing a host in all geographic areas. A few crop hosts are used throughout the range as expected, but in some cases there are anomalies, perhaps because host plant relation studies are not comparable. Studies on the attraction of heliothines to plant odors are examined in the context of our current understanding of insect olfaction, with the aim of better understanding the connection between odor perception and host choice. Finally, we discuss research into sustainable management of pest heliothines using knowledge of heliothine behavior and ecology. A coordinated international research effort is needed to advance our knowledge on host relations in widely distributed polyphagous species instead of the localized, piecemeal approaches to understanding these insects that has been the norm to date.
Spodoptera litura (F.) is an important pest of numerous agro-economic crops, including green manure cover crops. In Taiwan, sesbania (Sesbanin roxburghii Merr.), sunn hemp (Crotalaria juncea L.), and rapeseed (Brassicae campestris L. variety chinensis) are the most popular green manure crops; sesbania and sunn hemp are commonly planted in warm seasons, whereas rapeseed is grown in the winter. In this study, life-table data for S. litura reared on these three green manures were collected to evaluate their roles as refuges of this pest. The net reproductive rate, intrinsic rate of increase, and finite rate of increase of S. litura were the highest when reared on sesbania (1428.1 offspring, 0.2327 d-1, 1.2621 d-1), followed by sunn hemp (778.4 offspring, 0.2070 d-1, 1.2300 d-1) and rapeseed (737.6 offspring, 0.2040 d-1, 1.2263 d-1). The high growth rates on these green manure crops show that they can serve as potential breeding sites for S. litura. Population projection demonstrated the rapid growth of S. litura on sesbania, sunn hemp, and rapeseed as well. Because most growers have traditionally ignored pest management in green manure fields, the mass emergence of S. litura in these fields may cause unexpected infestations in nearby vegetable, corn, and peanut crops. This study shows that the use of green manures as sources of nutrients should be critically reassessed and an area-wide pest management program should be instituted by taking the population of S. litura in green manure fields into consideration.
Pupae of the blueberry maggot, Rhagoletis mendax Curran (Diptera: Tephritidae), were subjected to -20°C for 2, 4, 7, 10, and 15 d (control = 0 d at 4°C) in fall 2011 and 2012 and were allowed to overwinter for at least 181 d at 4°C. Mean adult emergence in the control was 64% in 2012 and 39% in 2013. No adults emerged in May 2012 from 500 pupae treated for >2 d at -20°C in fall 2011. Two adults emerged in May 2013 from 100 pupae treated for 2 d at -20°C in fall 2012. No adults emerged in May 2013 from 400 pupae subjected to -20°C for durations of 4, 7, 10, and 15 d. No adults emerged from larvae concealed in berries subjected to -20°C for >2 d. Exposure of larvae and pupae to cold temperatures (i.e., -20°C) for >2 d can be a valuable nonpesticidal method for killing R. mendax larvae and pupae associated with reusable containers.
Stefano Civolani, Stefano Cassanelli, Milvia Chicca, Jean L. Rison, Andrea Bassi, Juan M. Alvarez, I. Billy Annan, Giuseppe Parrella, Massimo Giorgini, Elisa Anna Fano
Cyantraniliprole is a novel insecticide for control of multiple chewing and sucking insect pest species including the sweetpotato whitefly Bemisia tabaci (Gennadius), which is one of the most important polyphagous pests in tropical, subtropical, and Mediterranean regions. This study aims to evaluate the effects of cyantraniliprole on the probing behavior of B. tabaci on tomato. Electrical penetration graph data indicated that on plants treated with cyantraniliprole (foliar application), adult whiteflies of the genetic variant Q2 were not able to reach the phloem and consequently did not perform the activities represented by E1 and E2 waveforms, i.e., phloem salivation (during which inoculation of geminiviruses occurs) and phloem sap ingestion (during which geminiviruses are acquired by the whiteflies), respectively. The complete failure of B. tabaci biotype Q adults to feed from the phloem of tomato plants treated with cyantraniliprole could be explained by rapid cessation of ingestion because of the mode of action of this insecticide. Overall, these findings indicated that cyantraniliprole might represent a useful new tool for producers to protect tomato plants from damage by B. tabaci.
Plant defense responses can greatly affect plant viruses and their herbivore vectors. The current article reports on plant defense responses involving jasmonic acid (JA), salicylic acid (SA), and proteinase inhibitor (PI) in the three-way interaction between tomato plants, tomato yellow leaf curl virus, and the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). The results showed that feeding by viruliferous B. tabaci increases the longevity and fecundity of nonviruliferous B. tabaci that subsequently feed on the same plant. Feeding by nonviruliferous B. tabaci alone suppressed plant defense responses involving JA and PI but induced responses involving SA. Feeding by viruliferous B. tabaci increased the suppression of plant defenses involving JA and PI but did not increase responses involving SA. These results indicate that the interactive effects of tomato yellow leaf curl virus and B. tabaci on plants increase vector fitness and virus transmission by reducing plant defense.
Laboratory studies were conducted to investigate tritrophic transfer of insecticidal Cry proteins from transgenic cotton to an herbivore and its predator, and to examine effects of these proteins on the predator's development, survival, and reproduction. Cry1Ac and Cry2Ab proteins from the bacterium Bacillus thuringiensis (Bt) produced in Bollgard-II (BG-II, Event 15985) cotton plants were acquired by Thrips tabaci Lindeman (Thysanoptera: Thripidae), an important sucking pest of cotton, and its generalist predator, Orius insidiosus (Say) (Hemiptera: Anthocoridae). The average protein titers in BG-II cotton leaves were 1,256 and 43,637 ng Cry1Ac and Cry2Ab per gram fresh leaf tissue, respectively. At the second trophic level, larvae of T. tabaci reared on BG-II cotton for 48–96 h had 22.1 and 2.1% of the Cry1Ac and Cry2Ab levels expressed in leaves, respectively. At the third trophic level, O. insidiosus that fed on T. tabaci larvae had 4.4 and 0.3% of the Cry1Ac and Cry2Ab protein levels, respectively, expressed in BG-II plants. O. insidiosus survivorship, time of nymphal development, adult weight, preoviposition and postoviposition periods, fecundity, and adult longevity were not adversely affected owing to consumption of T. tabaci larvae that had fed on BG-II cotton compared with non-Bt cotton. Our results indicate that O. insidiosus, a common predator of T. tabaci, is not harmed by BG-II cotton when exposed to Bt proteins through its prey. Thus, O. insidiosus can continue to provide important biological control services in the cotton ecosystem when BG-II cotton is used to control primary lepidopteran pests.
The interactions between the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Ascomycota: Hypocreales) and the aphid parasitoid Diaeretiella rapae McIntoch (Hymenoptera: Braconidae) were evaluated under laboratory conditions. Nymphs of Myzus persicae Sulzer (Hemiptera: Aphididae) were first exposed to parasitoid females for 24 h and then 0, 24, and 48 h afterwards sprayed with a solution of B. bassiana. Likewise, aphids were also sprayed with B. bassiana and then exposed to parasitoids at 0, 24, and 48 h afterwards. Parasitism rate varied from 13 to 66.5%, and were significantly lower in treatments where the two agents were exposed within a 0 -24 h time interval compared with the control (without B. bassiana). Parasitoid emergence was negatively affected in treatments with B. bassiana spraying and subsequent exposure to D. rapae. Decreases in longevity of adult females of the D. rapae F1 generation were observed in treatments with B. bassiana spraying. The application of these two biological control agents can be used in combination on the control of M. persicae, wherein this use requires effective time management to avoid antagonistic interactions.
Spathius galinae Belokobylskij & Strazanac is a recently described parasitoid of the emerald ash borer, Agrilus planipennis Fairmaire, in the Russian Far East, and is currently being considered for biocontrol introduction in the United States. Using A. planipennis larvae reared with freshly cut ash (Fraxinus spp.) sticks, we investigated the biology, life cycle, and rearing of S. galinae in the laboratory under normal rearing conditions (25 ± 1°C, 65 ± 10% relative humidity, and a photoperiod of 16:8 [L:D] h). Our study showed that S. galinae took approximately 1 mo (29 d) to complete a single generation (from egg to adult) under the laboratory rearing conditions. After éclosion from eggs, larvae of S. galinae molted four times to reach the fifth instar, which then spun cocoons for pupation and development to adults. Adult female wasps had a median survival time of 7 wk with fecundity peaking 3 wk after emergence when reared in groups (of five females and five males) and 2 wk in single pairs. Throughout the life span, a single female S. galinae produced a mean (±SE) of 31 (±3.0) progeny when reared in groups, and a mean (±SE) of 47 (±5.3) progeny when reared in single pairs. Results from our study also showed that S. galinae could be effectively reared with A. planipennis larvae reared in both green (Fraxinus pennsylvanica Marshall) and tropical [Fraxinus uhdei (Wenzig) Lingelsh] ash sticks. However, the abortion (unemergence) rate of S. galinae progeny was much higher (20%) when reared with host larvae in green ash sticks than that (2.1%) in tropical ash sticks.
The kudzu bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae), is a newly invasive exotic insect found primarily on kudzu, but also on soybean, in the southeastern United States. We used molecular gut-content analysis to document predation on this pest by insects and spiders in soybean, and to detect remains of crop-specific alternative prey in predators' guts as markers of predator migration between soybean and adjacent cotton. M. cribraria was found exclusively on soybean. Eight native generalist predators over both crops screened positive by specific PCR for DNA of the pest: Geocoris punctipes (Say), Geocoris uliginosus (Say), Orius insidiosus (Say), Podisus maculiventris (Say), Hippodamia convergens Guérin-Méneville, Zelus renardii (Kolenati), Oxyopes salticus Hentz, and Peucetia viridans (Hentz) ; a ninth predator, the exotic Solenopsis invicta Buren, also screened positive for M. cribraria DNA. P. viridans was the only arthropod that tested positive for DNA of this invasive pest in only one crop, cotton. Two plant-feeding pentatomid species, Piezodorus guildinii (Westwood) and Thyanta custator (F.), were found exclusively on soybean, and another, Euschistus tristigmus (Say), was specific to cotton in the context of this study. Detection of predation on a combination of M. cribraria and P. guildinii and T. custator in cotton and M. cribraria and E. tristigmus in soybean demonstrated that these predators dispersed between crops. These results strongly support the use of soybean habitats adjacent to cotton as part of a conservation biological control strategy against M. cribraria. This is the first report documenting predation on this exotic pest in the field via molecular gut-content analysis.
Trichogramma species and strains differ significantly in host specificity and performance. Nine Trichogramma strains, six of them collected from paddy fields in the Greater Mekong Subregion, were evaluated for performance on eggs of the striped stem borer, Chilo suppressalis (Walker), in both laboratory and field tests to determine potential Trichogramma strains that can be used in an inundative release in an integrated pest management program. In the laboratory glass vial tests, all strains showed higher parasitism rates on 0 -24-h eggs than on the two older age groups (24–48 and 48–72 h). Wasp emergence rate was also higher from parasitized 0-24-h striped stem borer eggs, while Trichogramma immature duration was significantly prolonged on 0-24-h striped stem borer eggs. Parasitism rates differed among Trichogramma strains, with Trichogramma chilonis Ishii CJ strain showing significantly higher parasitism rate than any other strains. In the field tests, parasitism of sentinel striped stem borer eggs by Trichogramma strains released at 50,000,100,000, and 200,000 wasps per hectare was low, with marginal yet significant differences between strains. The highest parasitism was achieved by T. chilonis CJ strain at the high and medium release rates. Hence, it can be concluded that T. chilonis CJ strain released at 100,000 wasps per hectare may be a cost-effective control tactic for field releases targeting striped stem borer.
Irradiation is a postharvest quarantine treatment option for exported commodities such as stone fruits and small fruits to prevent movement of the new invasive pest spotted wing drosophila, Drosophila suzukii (Walker) (Diptera: Drosophilidae). The effects of irradiation on larval and pupal development and adult reproduction in D. suzukii were examined. Larvae (first, second, and third instars) and pupae (1-2-d-old, 3-5-d-old, and 7-8-d-old) on diet were irradiated at target doses of 20, 30, 40, and 50 Gy in replicated factorial experiments and survival to the adult stage was recorded. Tolerance to radiation increased with increasing age and developmental stage. Males and females were equally susceptible. A radiation dose of 40 Gy applied to first- and second-instar larvae prevented adult emergence. The late-stage pupa was the most radiation-tolerant stage that occurs in fruit, and individuals irradiated at this stage readily emerged as adults; therefore, prevention of F1 adults was the desired treatment response for large-scale validation tests with naturally infested fruit. In large-scale tests, a radiation dose of 80 Gy applied to late-stage pupae in sweet cherries or grapes resulted in no production of Fl adults in >33,000 treated individuals, which meets the zero tolerance requirement for market access. A minimum absorbed dose of 80 Gy is recommended for quarantine control of D. suzukii.
The cotton bollworm, Helicoverpa armigera (Hübner), was recently introduced in Brazil. During the 2012-2013 harvest, producers reported reduced yields up to 35% on major crops. The economic losses reached US$ 1 billion only in western Bahia, triggering a phytosanitary crisis. The deficiencies in existing taxonomic keys to deal with the morphologically indistinct larvae of H. armigera and the native Helicoverpa zea (Boddie) constrained the detection of new incursions of this heliothine invader. This study explored the identity of heliothine larvae that were found infesting soybean- and corn-growing areas from Roraima state, northern Brazil, through sequences of the mitochondrial cytochrome c oxidase subunit I gene. The inter- and intraspecies sequence variations of DNA barcodes in H. armigera and H. zea were analyzed. The genetic diversity and population structure of the specimens from Roraima and two populations from Piaui and Bahia states, northeastern Brazil, were assessed by adding the cytochrome coxidase subunit II gene to the analysis. Owing to the lack of studies on genetic introgression for the two species, the suitability of using three different nuclear genes to distinguish the two species was also investigated. The results showed strong evidence that the heliothine larvae from north and northeast of Brazil are conspecific with H. armigera, suggesting that this invasive moth has already crossed the Amazon basin. Surveys in the north of South America should start as soon as possible to monitor the entry or spread of this moth in the Caribbean, Central America, and the United States.
A multiple quarantine treatment was developed to control Hessian fly puparia, Mayetiola destructor (Say), the stage of regulatory concern in exported hay. In a commercial test using 51,589 puparia, no insects survived to the adult stage after exposure to bale compression at 137 kg/cm2 and fumigation with 61 g/28.3 m3 hydrogen phosphide for 3d. The puparia were fumigated in infested wheat seedlings in cloth bags inside compressed timothy bales placed in different locations in three replicate freight containers in a heated building. Fumigant concentrations were 345-522 ppm on day 1; 580–824 ppm on day 2; and 680–861 ppm on day 3. Monitored temperatures were <20°C in all locations allowing the fumigation temperature to be established at ≥20C. Copper detection plate corrosion values were severe inside the freight container doors, and moderate in the middle of bales in all locations, providing visual confirmation of exposure to hydrogen phosphide. Hydrogen phosphide residues in exposed hay bales were found in trace amounts, below the U.S. Environmental Protection Agency tolerance of 0.1 ppm for animal feeds. Timothy hay used in the commercial test is the representative species for all previously exported hay and straw species. The new multiple quarantine treatment is proposed for use with all previously tested bale sizes and wrapper styles for which 3-d fumigation data has been reported, and for bales and wrappers derived from those tested.
We identified native bees that are floral visitors and potential pollinators of tomato in Cerrado areas, described the foraging behavior of these species, and verified the influence of the visitation of a solitary bee on the quantity and quality of fruits. Three areas of tomato crops, located in Minas Gerais, Brazil, were sampled between March and November 2012. We collected 185 bees belonging to 13 species. Exomalopsis (Exomalopsis) analis Spinola, 1853 (Hymenoptera: Apidae) was the most abundant. Ten species performed buzz pollination. Apis mellifera L. 1758 (Hymenoptera: Apidae) and Paratrigona lineata (Lepeletier, 1836) (Hymenoptera: Apidae) could also act as pollinators. The fruit set and number of seeds obtained from the pollination treatment by E. analis were higher than those in the control group. Our results allowed the identification of potential tomato pollinators in Cerrado areas and also contributed information regarding the impact of a single species (E. analis) on fruit set and quality. Although most of the visiting bees show the ability for tomato pollination, there is an absence of adequate management techniques, and its usage is difficult with the aim of increasing the crop production, which is the case for E. analis. Species such as Melipona quinquefasciata, P. lineata, and A. mellifera, which are easy to handle, are not used for pollination services. Finally, it is suggested that a combination of different bee species that are able to pollinate the tomato is necessary to prevent the super-exploitation of only a single species for pollination services and to guarantee the occurrence of potential pollinators in the crop area.
Athetis lepigone (Möschler), a new lepidopteran pest in China, has spread quickly to seven provinces since it was first reported causing damage on summer maize in Hebei province in 2005. Whether this species is a migrant or not remains unknown. The past 3 yr searchlight trapping on an island in the center of Bohai Gulf provided direct evidence that both male and female A. lepigone moths migrate across the Bohai Gulf waters in northern China because no host crops or A. lepigone larvae were found on this island. The four migration waves observed in this study represent high-altitude movements of the overwintering, first, second, and third generations of A. lepigone moths, respectively. Carbon isotope analysis showed that 1.76–5.44% of the tested A. lepigone moths originated from C4 plants, which provides additional evidence that this species is a migrant because there are no C4 plants on this small island. The 89.24–96.89% of tested A. lepigone moths originated from C3 plants were significantly higher than that from C4 plants in all generations, suggesting that maize fields are not the main host sites for A. lepigone. Few females were trapped in spring and early summer with relatively high mating frequency and more advanced ovarian development, suggesting that the migration of this species is not completely bound by the “oogenesis-flight syndrome.” These findings reveal a new route for A. lepigone migrating to and from the northeastern agricultural region of China, and improve our knowledge of the migration ecology of A. lepigone. Further studies are needed to clarify the migration trajectories that will help in developing sound forecasting systems for this pest species.
Ctenoplusia agnata (Staudinger) (Lepidoptera: Noctuidae) is an important polyphagous pest in East Asia. Previous studies showed that C. agnata moths possesses the potential to undertake long-distance migration; however, knowledge of whether or not the migration of C. agnata moths is a regular ecological behavior and what the pattern of seasonal migrations is in case of regular migration is currently lacking. In the current study, systemic monitoring of population dynamics of C. agnata was conducted by a searchlight trap on an island in the center of Bohai gulf in northern China, during 2003–2013. Our results provided strong evidence for the hypothesis that C. agnata is one of the pest species undertaking regular high altitude long-distance migration and we have depicted the seasonal migration pattern over the Bohai Sea. The first capture of C. agnata generally appeared in late April and early May, then the daily number of catches increased to high levels in late July and formed two waves of migration through August and early September, and finally, the moths disappeared in late October. The mean time from the earliest trapping to the latest trapping within a year was 141.0 ± 3.0 days. The index of ovarian development of female C. agnata showed seasonal variability and suggested that its migratory flight may be independent of the degree of ovarian development and mating status. In addition, strong migration events took place in 2003, 2004, 2008, and 2010 (annual sum of catches >10,000). The research result from this work is helpful for understanding the occurrence regularity of C. agnata and developing an integrated pest management strategy.
We studied Paysandisia archon (Burmeister) (Lepidoptera: Castniidae: Castniinae) courtship behavior to provide a detailed qualitative and quantitative description of male and female behaviors. Moreover, to investigate the role of antennal olfaction and visual stimuli in mate-recognition, bio assays with antennectomized adults and dummies were performed. To assess the presence of a pheromone gland in the ovipositor, morphological (using light and scanning electron microscopic techniques), electrophysiological, and chemical investigations were carried out. We observed perching mate-locating behavior of P. archon males, with the female triggering the courtship sequence by approaching the perching male first. The stereotyped courtship sequence is made up of five main steps: female flight, pair flight, alighting close, copulation attempt, and clasping. Our findings suggest that visual cues are important in P. archon courtship behavior, and the role of chemical cues is also discussed. Moreover, we observed a higher antenna cleaning frequency in females than in males. Ovipositor extrusions during courtship appeared not to be related to calling behavior, and histological investigations showed no evidence of glandular tissues involved in sex pheromone production. The P. archon ovipositor consists of the eighth uromere, which forms the ovipositor base, and the 9th and 10th uromeres are fused together and connected to the base by an intersegmental membrane. Overall, 24 compounds were identified from extracts obtained from ovipositors: 9 compounds were detected only in extracts from the ovipositors of 24-h-old virgin females, and not from those of 1-h-old females. None of these compounds elicited any significant electrophysiological responses from male antennae.
The physiological state of an insect is likely the most important endogenous factor influencing resource-oriented behavior, and it varies considerably among individuals. Trials were conducted in mango orchards to study the effect of multiple endogenous biological factors on the response of two fly species, Anastrepha ludens (Loew) and Anastrepha obliqua Maquart (Diptera: Tephritidae), to BioLure and NuLure baits. The biological factors of the two fly species that were tested were the following: 1) fertility status—sterile (irradiated) and fertile flies; 2) two types of diets (only sugar and a 3:1 mixture of sugar and hydrolyzed yeast protein; 3) sex, and 4) two sexual maturity conditions (2–4- and 15–18-d-old flies, representing immature and sexually mature flies, respectively, and 2–4-d-old flies treated with methoprene as an artificially induced sexually state male condition). The laboratory-treated flies were released into three different mango orchards. The trials were conducted in four blocks per orchard using eight traps in each block (50:50 BioLure: NuLure). The traps were replaced every 2 d during the 12-d period and the flies per trap per day values were calculated. More protein-fed, fertile, female, immature, and A. obliqua flies were caught compared with the other flies tested. In addition, the traps baited with NuLure attracted more flies than those baited with BioLure. Interaction analyses indicated that the type of bait and the sexual maturity status were the most important factors affecting the responses of the flies. Our study demonstrated that lures attract only a small segment of the fly population, those that have a specific hunger for amino acids—immature flies—and those that were protein-starved. The implications for improved trapping system designs are discussed.
Sweet cherries, Prunus avium (L.) L., grown in the western United States are exported to many countries around the world. Some of these countries have enforced strict quarantine rules and trade restrictions owing to concerns about the potential establishment and subsequent spread of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), a major quarantine pest of sweet cherry. We used 1) niche models (CLIMEX and MaxEnt) to map the climatic suitability, 2) North Carolina State University-Animal and Plant Health Inspection Service Plant Pest Forecasting System to examine chilling requirement, and 3) host distribution and availability to assess the potential for establishment of R. indifferens in areas of western North America where it currently does not exist and eight current or potential fresh sweet cherry markets: Colombia, India, Indonesia, Malaysia, Taiwan, Thailand, Venezuela, and Vietnam. Results from niche models conformed well to the current distribution of R. indifferens in western North America. MaxEnt and CLIMEX models had high performance and predicted climatic suitability in some of the countries (e.g., Andean range in Colombia and Venezuela, northern and northeastern India, central Taiwan, and parts of Vietnam). However, our results showed no potential for establishment of R. indifferens in Colombia, Indonesia, Malaysia, Taiwan, Thailand, Venezuela, and Vietnam when the optimal chilling requirement to break diapause (minimum temperature ≤3°C for at least 15 wk) was used as the criterion for whether establishment can occur. Furthermore, these countries have no host plant species available for R. indifferens. Our results can be used to make scientifically informed international trade decisions and negotiations by policy makers.
Using the age-stage, two-sex life table, the effects of three ligustrum species, Ligustrum × vicaryi Hort., Ligustrum quihoui Carrière, and Ligustrum lucidum Aiton, on the fitness of Problepsis superans (Butler, 1885) (Lepidoptera: Geometridae) were assayed by considering life table parameters of P. superans at 27 ± 1°C, 70 ± 5% relative humidity, and a photoperiod of 16:8 (L: D) h. The means and SEs of population parameters were calculated using the jackknife and bootstrap methods. The total developmental time of larval stage of P. superans on L. × vicaryi was significantly shorter than that on L.. × vicaryi and L. quihoui, whereas higher fecundity was observed on L. × vicaryi. The highest value of the finite rate of increase was observed on L. × vicaryi. The intrinsic rate of increase of P. superans on L. × vicaryi, L. quihoui, and L. lucidum, was 0.147 ± 0.004, 0.130 ± 0.004, and 0.112 ± 0.005, respectively, which differed significantly among the three ligustrum species. The net reproductive rate varied from 122.8 ± 24.7 female offspring on L. lucidum to 242.2 ± 36.2 female offspring on L. × vicaryi. The lowest mean generation time was observed on L. × vicaryi. The gross reproductive rate of P. superans on the three ligustrum species did not significantly differ. Based on growth and population parameters, the suitability of the three ligustrum species to P. superans is ranked from high to low in the order as L. × vicaryi, L. quihoui, and L. lucidum.
Changes in protein, lipid, and carbohydrate content, and the weight loss of soybean seeds caused by the feeding of 6- to 7-d-old unmated male adults of the pentatomids Peizodorous hybneri (Gmelin) and Halymorpha halys (Stål), and an alydid, Riptortus pedestris (F.), were examined in the laboratory. Our goals were to determine which species had the greatest capacity to damage soybean seed and to measure the effect of that damage on the nutritional composition of soybean seed. Individuals of the three species were provided with a preweighed dry soybean seed and allowed to feed for 0, 4, 8, 12, 16, 20, and 24 d, after which the remaining seed was analyzed for any change in weight, protein, lipid, and carbohydrate concentration. Lipids, carbohydrates, and seed weights were reduced by bug feeding, and the reduction was directly proportional to feeding duration. H. halys was found to be the most voracious feeder, reducing soybean seed weight by 42% after 24 d of feeding. There was a significant interaction between species and feeding duration for changes in nutritional components. Seeds fed on by H. halys had the highest incremental increase in protein content (13%) after 24 d of feeding, followed by those fed on by R. pedestris and P. hybneri. However, carbohydrates and lipid content of the soybean seeds fed by the tested insect species were found to decrease significantly. Soybean pods at mature stages remain in the field for a long period, and findings of our study suggest that longer exposure of the mature soybean pods to these pest species in the field may lead to low-quality seeds and lower yields, and may even affect the germination potential of the seeds.
The reported male-produced aggregation pheromone of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), identified as a mixture of (3S,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol and (3R,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol, offers new opportunities for its management. We found that black pyramid traps deployed along crop borders in Maryland and West Virginia, containing lures with both stereoisomers of this reported aggregation pheromone combined with methyl (E,E,Z)-2,4,6-decatrienoate (MDT) lures, attracted more adult and nymphal H. halys than either the aggregation pheromone or MDT alone. In season-long totals, combined lures acted synergistically by catching 1.9–3.2 times more number of adults, and 1.4–2.5 times more number of nymphs, than expected from an additive effect of the lures deployed individually. There were no significant differences in patterns of male and female captures. MDT alone was not significantly attractive to adults during most of the growing season, but became increasingly attractive to adults and especially nymphs in autumn. Mixed-isomer lures containing eight stereoisomers of 10,11-epoxy-1-bisabolen-3-ol, including the two active stereoisomers, were as effective at catching adults and nymphs with or without MDT as were lures loaded only with the two active stereoisomers in the natural ratio ((3S,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol: (3R,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol) of 3.5:1. These results identify a combination of semiochemicals that is attractive season-long for detection, monitoring, and potential control of this polyphagous invasive pest of North America and Europe.
Among the insects reported in biofuel crops, the yellow sugarcane aphid, Sipha flava (Forbes), is a potential pest of giant miscanthus, Miscanthus × giganteus Greef et Deu ex Hodkinson et Renvoize (M×g) and energy cane “L79-1002”, Saccharum spp. L. We studied the biology of S. flava on M×g and energy cane and estimated the development period, fecundity, longevity, intrinsic rate of increase, doubling time, reproductive value, and survivorship curves. To demonstrate the host suitability in a susceptible species, we studied the aphid life table on sorghum ‘PL 18200,’ Sorghum bicolor (L.) Moench. Life-table information was recorded under greenhouse conditions on the host plants. Our results suggested that both M×g and energy cane are suitable hosts for S. flava. We observed similar aphid development period on both hosts. Life-table estimates including longevity and fecundity suggested that M×g is a more suitable host for the aphid than energy cane. The intrinsic rate of increase for S. flava was lower on energy cane (0.231) than on M×g (0.258).
Insects that reproduce sexually must locate a suitable mate, and many species have evolved efficient communication mechanisms to find each other. The number of reproductively viable individuals in a population can be an important constraint in the growth of populations. One factor that can affect insect fecundity is the age of mating adults, as fecundity tends to decline with age. Field observations collected annually on Lymantria dispar (L.) from 2001 to 2007 and 2009 consistently revealed a small proportion of egg masses (generally <10% in each year) in which >0 but <5% of eggs were fertilized in an egg mass consisting of ≈200–500 eggs. In these studies, male age was unknown but female age was fixed at <24 h, which, according to previous studies on the effect of female L. dispar age on reproductive success, should have been optimal for fertilization. In this article, we analyzed field data (2001–2007 and 2009) to explore patterns in the occurrence of low-fertilized egg masses.We supplemented these data with laboratory experiments that examined the interacting role of male and female age, and multiple male matings. We observed that increases in male and female age reduce the rate of fertilization, which is furthermore reduced, as males mate multiple times as they age. This article highlights the importance of both female and male age at the time of mating in an invading species, with ramifications to low-density populations in this and other sexually reproducing insect species.
We developed new integrated pest management programs for eastern U.S. peaches with minimal use of organophosphates. From 2002–2005, we assessed the ecological impacts of these reduced-risk programs versus grower standard conventional programs that still relied primarily on the use of organophosphorous and carbamate insecticides. Using a split-plot design replicated at four commercial Pennsylvania peach orchards, we quantified pesticide rates, environmental impact, and arthropod community response. We used Environmental Impact Quotient (EIQ) analysis based on the growers' pesticide records from each orchard to calculate seasonal cumulative EIQ field ratings for all years. Ecological effects of the reduced-risk and conventional program were also measured as the abundance and diversity of nontarget arthropod predators, parasitoids, and selected pest taxa. Pesticide inputs and EIQ values were substantially lower in reduced-risk programs compared with conventional spray programs. Arthropod arrays differed significantly between pest management programs: most beneficial predator and parasitoid taxa were positively associated with the reduced-risk program and negatively associated with the standard grower program. Regardless of the pest management program, we observed significant differences in species arrays in the peach tree canopy compared with the ground cover of the orchards, but the arthropod community did not differ among the field sites or based on distance from the edge of the orchard. We conclude that reduced-risk programs not only provide control comparable with that of conventional programs, but they also reduce negative environmental effects while conserving key arthropod biological control agents within eastern U.S. peach orchards.
Mold contamination is an important issue in insect mass rearing. Frequently used antifungal agents such as sorbic acid and methylparaben have negative impact on many lepidopteran larvae, which might be one of the reasons for the difficulty in rearing rice leaffolder, Cnaphalocrocis medinalis (Güenée). In this study, 19 antifungal agents, including 7 food preservatives, 6 antifungal drugs, and 6 agricultural fungicides, were screened for their inhibitory activities on Aspergillus niger in diets. The results demonstrated that most of the tested chemicals are unsuitable as mold inhibitors in the diets of the rice leaffolder, and the rice leaffolder neonate is sensitive to sorbic acid and methylparaben. These two mold inhibitors at commonly used concentrations were shown to impact the survival of rice leaffolder larvae fed on artificial diets. Among the tested mold inhibitors, natamycin was the safest for the rice leaffolder larvae. Much higher larva survival was observed for the larvae fed on diets containing natamycin as an antifungal agent (59 and 72% at 200 and 400 ppm, respectively). Two agricultural fungicides, tebuconazole and azoxystrobin, are also potent as mold inhibitors when used in insect diets. The mixed use of natamycin and sorbic acid, or methylparaben, and the mixed use of sorbic acid and azoxystrobin resulted in significantly higher larva survival than sorbic acid methylparaben. Natamycin azoxystrobin and sorbic acid tebuconazole resulted in larva survival similar to that of sorbic acid methylparaben. The ternary combination of natamycin, sorbic acid, and methylparaben was the best combination for the rearing of rice leaffolder.
Transgenic corn, Zea mays L., hybrids expressing insecticidal Cry proteins from Bacillus thuringiensis (Bt) and insecticide applications to suppress injury from Helicoverpa zea (Boddie) were evaluated in Florence, SC, and in Plymouth, NC, in 2012 and 2013. Based on kernel area injured, insecticide applications (chlorantraniliprole) every 3–4 d from R1 until H. zea had cycled out of corn reduced injury by 80–93% in Florence and 94–95% in Plymouth. Despite intensive applications of insecticide (13–18 per trial), limited injury still occurred in all treated plots in 2012, except in DKC 68-03 (Genuity VT Double PRO), based on kernels injured (both locations) and proportion of injured ears (Florence only). In 2013, ear injury was low in Plymouth, with no kernel injury in any insecticide-treated plots, except P1498R (non-Bt) and P1498YHR (Optimum Intrasect). Injury in Florence in 2013 did not occur in treated plots of DKC 68-04 (non-Bt), DKC 68-03 (Genuity VT Double PRO), and N785-3111 (Agrisure Viptera). Yields were not significantly affected by insecticide treatment and were not statistically different among near-isolines with and without Bt traits. Yields were not significantly associated with kernel injury based on regression analyses. The value of using Bt corn hybrids to manage H. zea is discussed.
Pheromone traps have been widely used to monitor insect population activity. However, sticky pheromone traps for the Hessian fly (Mayetiola destructor), one of the most destructive pests of wheat, have been used only in recent years. Hessian fly male adults are small and fragile, and preserving specimens during sorting of sticky pheromone traps is a challenge when intact specimens are often required to visually distinguish them from related insects such as fungus gnats. In this study, we have established a quick and reliable method based on polymerase chain reaction markers to correctly distinguish Hessian fly males from other closely related insects. Two Hessian fly-specific markers were established, one based on the trypsin gene MDP-10 and the other based on a gene encoding the salivary gland protein SSGP31-5. Both markers provided >98% identification success of 110 Hessian fly samples prepared from single insects. The method should provide a useful tool to allow for identification of Hessian fly individuals on sticky pheromone traps or in other situations when Hessian fly eggs, larvae, pupae, and adults are difficult to distinguish from other insects.
The aim of this work was to determine the efficiency and feasibility of two different watermelon pest control systems on pest infestations, natural enemies, and on the productivity and sustainability of watermelon cropping. Two independent experiments were carried out during the dry season of 2011. Both experiments were carried out using a randomized block experimental design, with three treatments; weekly application of pesticide (WAP), integrated pest management (IPM), and nonpesticide application (control); and four replicates. Arthropods sampling was performed every 2 d by direct counting at five randomly selected points in each plot. Samples were taken by beating the leaves from the apical portion of the plant against a white plastic tray. Arthropods that moved along the soil surface were sampled weekly using pitfall traps. Both WAP and IPM treatments negatively affected the arthropod population. We conclude that IPM is an attractive strategy for watermelon cropping both economically and environmentally because it provides the grower with an option to lower production cost, achieves the same production, and there is less need for pesticide application when compared with the prophylactic control treatment when pesticides are applied on a weekly basis. This has not been reported for watermelon before.
The goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is native to southern Arizona and is an invasive wood-boring beetle that has caused considerable mortality to native oak species in southern California. Assessing the dispersal capabilities of this woodborer may help to determine its potential environmental and economic risk within the invaded region, and possibly assist with the development of species-specific management strategies. The flight performance of A. auroguttatus adults under different age, mating, and nutritional status was assessed by tethering individuals to computerized flight mills for a 24-h trial period to collect information on total distance flown, flight times and velocities, number and duration of flight bouts, and postflight weight. The nutritional status and body size (i.e., elytron length) of A. auroguttatus adults had a significant influence on overall flight performance. Mating status and gender had no significant influence on total flight distance, duration, velocity, and flight bout time. Significant interactions between nutritional status and age were observed in the overall flight performance of A. auroguttatus, with decreased flight activity in old (≈6 d of age) starved individuals during a 24-h trial period. Overall, results of these flight mill assays indicate that A. auroguttatus is unable to disperse long distances across habitats that lack suitable oak hosts. This work supports the hypothesis that human-aided transportation via infested oak firewood from southern Arizona across the Sonoran desert likely caused the initial introduction, and subsequent satellite infestations of A. auroguttatus within southern California's native oak woodlands.
The reliability of the empirical phenology model proposed by Nam et al. (2013) was tested using spring emergence data of Thecodiplosis japonensis Uchida et Inouye (Diptera: Cecidomyiidae) from 1986 to 2011 in Yeongcheon, Korea. First, the lower developmental threshold temperature (LDT) was estimated using spring emergence of T. japonensis and field temperatures. Then a degree-day model to predict spring emergence of T. japonensis was constructed, based on LDTs estimated from field observations and laboratory temperature-dependent development data. Based on field observations, the estimated LDT value for postdiapause development of T. japonensis was 6.1°C, only 0.2°C higher than that estimated from laboratory data. The explanatory power of the empirical degree-day model constructed on the basis of LDT from field observations was 87.2%, similar to the 87.0% of a degree-day model based on laboratory data, suggesting that both models had similar explanatory power. Furthermore, the predictions of median date of emergence in both models were only five days earlier than the observed median date in 2011. These results show that the empirical phenology model based on field observations is a reliable method for predicting the phenology of insects.
The United States has a rich fauna of native Siricidae (wood wasps), but they are rarely studied because they have limited economic impact. In 2004, a non-native wood-boring pest, Sirex noctilio F., was found established in North America. Because S. noctilio is an economically important pest in pine plantations throughout the Southern Hemisphere, interest in the ecology of American native wood wasp populations has increased. A study was conducted during fall 2011 to investigate the effects of forest stand type and characteristics on native wood wasp abundance, and to describe their flight phenology in northeastern Mississippi. In total, 609 native wood wasps were captured, consisting of 608 Sirex nigricornis F. and one Urocerus cressoni Norton. There were significant treatment and location effects that influenced wood wasp abundance. The flight period of wood wasps captured in our study (October–December) was similar to studies in the southeastern United States, but differed from results in Minnesota and the northeastern United States (June–October).Woodwasp abundance was significantly correlated with higher basal area, smaller tree diameter at breast height, and shorter trees, all indicators of forest stand stress. It appears proper silvicultural management of pine plantations may reduce native wood wasp population abundance in the southeastern United States, as it does to S. noctilio in the Southern Hemisphere. We propose implementing management models used for the southern pine beetle to reduce stand hazard of future infestations of native and invasive wood wasps.
Bemisia tabaci (Gennadius) is an economically important pest of agricultural and ornamental plants worldwide and is now widely recognized as a cryptic species complex. In North America, B. tabaci is a particularly important pest of greenhouse poinsettia. In poinsettia production, two cryptic species from the B. tabaci complex, Mediterranean and Middle East Minor 1, often infest crops simultaneously. Differences in pesticide susceptibility between these two cryptic species have the potential to influence growers' management decisions, including the use of biological control or insecticides, and the choice of insecticide active ingredient. However, the demographic behavior of mixed-species infestations in commercial greenhouses has yet to be investigated. We conducted a survey of B. tabaci populations in commercial greenhouses in Ontario, Canada, and provide evidence that under biological control-based management, Middle East Minor 1 can displace Mediterranean, whereas under insecticide-based management Mediterranean populations will persist. Furthermore, we comment on implications of this behavior on the management of B. tabaci, and comment on methods used to identify B. tabaci cryptic species.
The reproduction of lowbush blueberry (Vaccinium angustifolium Aiton) is closely tied to insect pollination, owing to self-incompatibility. Many species are known to have greater pollination efficiency than the introduced Apis mellifera L., commonly used for commercial purposes. In this study, we measured the pollen loads of several antophilous insect species, mostly Apoidea and Syrphidae, present in four lowbush blueberry fields in Lac-St-Jean, Québec. To measure pollen loads and species specificity toward V. angustifolium, we net-collected 627 specimens of pollinators, retrieved their pollen loads, identified pollen taxa, and counted pollen grains. We found that the sizes of pollen loads were highly variable among species, ranging from a few hundred to more than 118,000 pollen grains per individual. Bombus and Andrena species in particular carried large amounts of Vaccinium pollen and thus may have greater pollination efficiency. Also, two species (Andrena bradleyi Viereck and Andrena Carolina Viereck) showed nearly monolectic behavior toward lowbush blueberry. Finally, we identified alternative forage plants visited by native pollinators, notably species of Acer, Rubus, Ilex mucronata, Ledum groenlandicum, and Taraxacum. Protecting these flowering plants should be part of management practices to maintain healthy pollinator communities in a lowbush blueberry agroecosystem.
The idea of enhancing insecticide efficacy against phytophagous insects with feeding stimulators was proposed as early as the 1960s, and a number of insect feeding stimulators based on sugars, molasses, and cottonseed extracts, biologically active at relatively high (5% and higher) concentrations, have been advocated. Here, we show that an acidic amino acid, L-aspartate, stimulates feeding in codling moth neonates at much lower concentrations and acts as an effective tank-mixed additive for increasing efficacy of insecticides, reducing fruit damage, and increasing yield of the fruit. In laboratory experiments, 1 mg/ml L-aspartate increased foliage consumption by 40–60% and, when added to Assail 30 SG, Baythroid XL, Delegate WG, or Garbaryl 80S, maintained its feeding stimulatory properties and reduced LD50s by ≈10 times. In a 3-yr field trial, addition of L-aspartate to the aforementioned insecticides at 395 g/ha reduced fruit damage from ≈6%, on average to <1% for first-generation codling moth, and from ≈20 to ≈5% for the second generation. Interestingly, addition of L-aspartate also increased the average weight of apples by 11–27%, as measured at the time of harvest.
The sterile insect technique has been routinely used to eradicate fruit fly Bactrocera tryoni (Froggatt) incursions. This study considers whether fly quality in a mass-rearing facility can be improved by reducing irradiation doses, without sacrificing reproductive sterility. Pupae were exposed to one of five target irradiation dose ranges: 0, 40–45, 50–55, 60–65, and 70–75 Gy. Pupae were then assessed using routine quality control measures: flight ability, sex ratio, longevity under nutritional stress, emergence, and reproductive sterility. Irradiation did not have a significant effect on flight ability or sex ratio tests. Longevity under nutritional stress was significantly increased at 70–75 Gy, but no other doses differed from 0 Gy. Emergence was slightly reduced in the 50–55,60–65, and 70 -75 Gy treatments, but 40–45 Gy treatments did not differ from 0 Gy, though confounding temporal factors complicate interpretation. Reproductive sterility remained acceptable (>99.5%) for all doses—40–45 Gy (99.78%), 50–55 Gy (100%), 60–65 Gy (100%), and 70–75 Gy (99.99%). We recommend that B. tryoni used in sterile insect technique releases be irradiated at a target dose of 50–55 Gy, providing improved quality and undiminished sterility in comparison with the current 70–75 Gy standard while also providing a substantial buffer against risk of under dosing.
We evaluated a combination of noninsecticidal alternatives to control trunk-damaging dogwood borer, Synanthedon scitula (Harris), consisting of novel barrier technologies, used alone or in combination with mating disruption. Barrier formulations evaluated included fibrous barriers of nonwoven ethylene vinyl acetate (EVA) and nonfibrous barriers of rubberized paint (elastomer) used in building coatings. To examine efficacy of dogwood borer control in orchards, all barrier trials were replicated in field tests, both in combination with mating disruption and without it. Trunk inspections to determine whether mating disruption and barriers effectively reduced actual tree infestation showed pheromone disruption significantly reduced infestation compared with the untreated check, but was not as effective as trunk handgun sprays of chlorpyrifos. EVA trunk barriers were effective in preventing borer infestation compared with untreated trees. The elastomer did not differ from the check or the EVA treatment. There was no interaction between disruption and barrier treatments. Barrier field life and durability was assessed over 2 yr by comparing degradation over time due to weathering and other environmental effects including animal damage. The EVA persisted and remained more intact than the elastomer, but was in need of reapplication after 2 yr. Barriers were also screened for efficacy against voles in small-plot trials in nonorchard locations with known high vole pressure; they were tested either alone, combined with a repellent (thiram), or, in the case of the elastomer only, combined with an abrasive (sand). Only the EVA significantly lowered vole chewing damage relative to the untreated checks.
The potato psyllid, Bactericera cockerelli Sulc, also known as tomato psyllid, is a serious pest of solanaceous plants. Its host selection criteria are poorly understood. In this study, we tested whether the Solanum habrochaites (PI127826), a wild solanaceous plant known for its property to repel whiteflies, was repellent to potato psyllids. Using a combination of nonchoice assays and choice assays on different psyllid stages, we demonstrated that S. habrochaites is both repelling and toxic to potato psyllids compared with Solanum lycopersicum. However, those properties were not sufficient to avoid transmission of the plant bacterial pathogen “Candidatus Liberibacter solanacearum” vectored by potato psyllids, the causative agent of potato zebra chip disease. However, a lower bacterial transmission rate to S. habrochaites was observed compared with S. lycopersicum.
Obscure mealybug is a pest of grapes in the cool climate regions of coastal California, is found on some vineyard weeds, and is tended by the Argentine ant. A study was conducted at a vineyard in Arroyo Grande, CA, to evaluate the impact of weeds on ant activity on grapevines, and the role that ants and weeds have on obscure mealybug infestation in grape clusters. The incidence of the fungus Botrytis cinerea was recorded as well. Treatments were weed exclusion versus the presence of weeds, and ant exclusion versus the presence of ants. Ant activity was evaluated weekly using sugar-based monitoring stations, and mealybug infestation and Botrytis incidence of clusters were evaluated at harvest. Ant exclusion reduced the overall number of ant visits by 82%, and ants increased mealybug infestation of clusters by 53%. Ant activity was 33% higher in the weeds treatment, but there was no impact of weeds on mealybug infestation. We suggest that the higher ant activity recorded in the weeds treatment may have been an artifact of the sugar-based sampling method. Botrytis incidence was three times higher with ants, but did not differ between weeds and weed exclusion treatments. The study supports other research showing a relationship between mealybug infestation and the presence of ants, as well as the lack of impact of floor vegetation on mealybug infestation of grape clusters. It is the first report of a relationship between ants and Botrytis, although it is more likely that the higher Botrytis incidence found here is a result of increased mealybug density than a direct effect by ants.
A durable termite bait containing 0.5% noviflumuron was evaluated for physical durability, retention of active ingredient, consumption by termites, and toxicity to termites over 5 yr in field studies at locations in Indiana, Mississippi, and South Carolina. Plots in Indiana and Mississippi included both natural rainfall and irrigated plots, while plots in South Carolina received only natural rainfall. Samples collected every 3 mo for the first 4 yr were evaluated for consumption with a 7 d no-choice bioassay using Reticulitermes flavipes (Kollar). Consumption and toxicity of 5 yr samples were evaluated in similar bioassays conducted for 42 d. Durable baits received from field sites had some cracking, and a small amount of external flaking, but no major deterioration based on visual observation. There were no significant differences in noviflumuron concentration over the 5-yr period and no trend toward reduced concentrations of noviflumuron over time. Consumption of aged durable baits over 4 yr was variable, but termites usually consumed more aged durable bait than fresh durable bait and the differences were frequently significant. There were some exceptions, but termites consumed significantly more fresh durable bait than aged durable bait in only 4% of observations. When 5 yr samples were evaluated, consumption was lowest for fresh durable bait and termites consumed significantly more aged durable bait from irrigated plots in Indiana and from both natural and irrigated plots in Mississippi than fresh durable bait. Survival of termites fed blank durable bait was significantly higher than that for termites fed any of the baits containing noviflumuron and there were no significant differences in survival among the noviflumuron durable baits. Our results suggest that the bait would be durable for at least 5 yr and possibly longer under most environmental conditions.
Fresh and aged residual deposits of several insecticide products were tested against bed bug adults to determine if a recent bloodmeal affected their mortality response to the residues. The bed bugs with a recent bloodmeal survived significantly longer compared with the unfed ones on their exposure to fresh or aged residual deposits of chlorfenapyr and aged residual deposits of deltamethrin on a wooden substrate. Even though the survival time of fed bed bugs was significantly longer than that of unfed ones on their exposure to fresh residue of deltamethrin and aged residue of desiccant pyrethrin dust, these treatments resulted in similarly high final mortalities regardless of feeding status of the insects. Mortality responses of fed and unfed bed bugs were similar to fresh or aged residual deposits of imidacloprid cyfluthrin combination and fresh residual deposits of desiccant pyrethrin dust. Topical application assays indicated that a recent bloodmeal significantly increased the bed bug’s survival time for chlorfenapyr, but not for deltamethrin. Pyrethro id-resistant bed bugs also showed a similar increase in their survival time for chlorfenapyr after a bloodmeal. The comparison of mortality responses between fed and unfed bed bugs treated with similar amount of chlorfenapyr per fresh body weight indicated that increased body mass was not the primary cause for this bloodmeal-induced tolerance increase for chlorfenapyr. Because the surviving bed bugs can continue ovipositing, the effectiveness of chlorfenapyr residual deposits in bed bug harborages could be significantly affected by the feeding status of the adult bed bug populations.
The effects of the juvenile hormone analog pyriproxyfen (at concentrations of 0.1, 0.5, and 1%) on egg production, number of ovarioles, and length of oocytes were examined in queens of the Pharaoh ant Monomorium pharaonis (L.). Pyriproxyfen significantly reduced egg production in queens from week 3 onwards. Queens that were exposed to 1% pyriproxyfen stopped producing eggs at week 8. After 8 wk, ovaries were dissected from all queens, and the number of ovarioles and the length of the largest oocytes were recorded. The ovaries of queens in treated colonies were smaller than those in untreated queens, and the number of ovarioles in the ovaries was significantly lower in all pyriproxyfen-treated queens. Queens treated with the highest concentrations of pyriproxyfen tended to have significantly shorter oocytes than untreated queens. Histological studies of the ovaries revealed that pyriproxyfen caused vacuolation in the ovarioles, thickening of the tunica propria, development of small eggs, and underdevelopment of nurse cells and the follicular epithelium. Exposure to pyriproxyfen reduced egg production and induced severe morphological changes in the ovaries of queens, and the effects increased with increased concentration of pyriproxyfen.
Trehalase is the hydrolytic enzyme that catalyzed the hydrolysis of trehalose to glucose. In this study, trehalase activity in the fungus-growing termite, Odontotermes feae Wasmann had been examined. Trehalase activity in digestive tract and carcass of O. feae was higher than that in woodfeeding termite, Coptotermes gestroi Wasmann. The intestinal tract of worker caste of O. feae was the main source of trehalase compared with that in salivary, fat body, and carcass. In particular, the highest activity was found in the midgut and hindgut parts. More specifically, the contents of midgut and hindgut had higher enzyme activity compared with that trehalase prepared from their epithelial tissue. The enzyme activity of gut trehalase in three different termite castes, worker, soldier, and reproductive, had been determined. The result showed that female alate had the highest activity, followed by worker, male alate, and soldier castes. Trehalose concentration in the reproductive caste was at lowest level, while soldier and worker contained the high trehalose concentration. This study indicates that high trehalase activity locates in the midgut and hindgut contents and change in trehalase activity in fungus-growing termite is caste-specific. Validamycin inhibited trehalase activity of O. feae in vivo and caused high mortality, indicating that this trehalase inhibitor is valuable tools for termite control.
The oriental fruit fly, Bactrocera dorsalis (Hendel), is a globally important economic insect pest that has evolved resistance to various types of insecticides. Cyantraniliprole (DuPont Cyazypyr) is a new anthranilic diamide insecticide registered to control lepidopteran and sucking insects. The susceptibility of field-collected populations of B. dorsalis to cyantraniliprole was assessed via a diet incorporation bioassay in adults. Based on the obtained LC50 values (ranging from 3.29 to 15.83 µg/g), all the testing populations, including ZZ (Fujian province), HH (Yunnan province), JM (Guangdong province), SY (Hainan province), HZ (Zhejiang province), YL (Guangxi province), SH (Shanghai), WH (Hubei province), and CS (Hunan province), were susceptible to cyantraniliprole, with the samples of WH (Hubei province) being the most tolerant (by 4.80-fold). Two (SY, Hainan province; CS, Hunan province) of the nine field-collected populations of B. dorsalis showed a similar susceptibility to cyantraniliprole, while the remaining populations displayed narrow variations in tolerance compared with the laboratory strain. Synergist assays were performed to determine the potential detoxification mechanisms. Piperonyl butoxide showed significant synergism effects in lab, CS, and resistant strain. S,S,S-tributylphorotrithioate and diethyl maleate also showed obvious synergism effects in resistant strain. A 19.44-fold increase in resistance to cyantraniliprole was observed after 14 generations of selection in the laboratory. The present work clarifies the baseline susceptibility and primary mechanisms of B. dorsalis to cyantraniliprole in the south China and established a cyantraniliprole-resistant strain as well. A sound resistance management strategy is also discussed in relation to the risk of susceptibility.
Western flower thrips, Frankliniella occidentalis (Pergande), is an economically important pest all over the world. New products against thrips are necessary, as there are few effective compounds exhibiting cross-resistance among them. Lethal effects, cross-resistance, and baseline susceptibility to spirotetramat were evaluated in this study. A new bioassay method for testing thrips against spirotetramat was developed. Spirotetramat showed a significant mortality effect on larvae after 7 d of exposure, but a low effect was observed on adults. Baseline results for larval instars showed LC50 values ranging from 11.59 to 49.81 mg AI/liter, with a low natural variability (3.2-fold). Cross-resistance studies showed overlapping confidence limits of the LC50 values for laboratory-selected (against acrinathrin, methiocarb, formetanate, and spinosad) resistant and susceptible strains, and low resistance factors, from 0.5 to 1.9, suggesting no cross-resistance to conventional insecticides previously used. A slight ovicidal effect (21–40% reduction) was also detected. Despite presenting low effects on adults, spirotetramat showed high but slow efficacy on F. occidentalis larvae. Field populations in southeast Spain showed a consistent susceptibility to spirotetramat. Given the scarcity of effective products and the lack of cross-resistance to other insecticides, spirotetramat can be considered as a good chemical tool to control F. occidentalis.
The European grapevine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae), is the key pest of vineyard, Vitis vinifera L. In Italy, failures in field chemical pest control have been recently reported. The susceptibility to insecticides indoxacarb, methoxyfenozide, and emamectin benzoate was then evaluated in a L. botrana population collected from a vineyard in Emilia-Romagna (northeastern Italy) where pest management programs achieved unsatisfactory results. The field trial showed that the indoxacarb efficacy toward L. botrana was very low in the two timings of application (7.9 and -1.5%) in comparison with untreated control, while the efficacy of methoxyfenozide (76.1%) and emamectin benzoate (88.8%) was high. The decreased efficacy of indoxacarb was also supported by the results of the laboratory bioassay on neonate L. botrana larvae, in which the resistance ratio was 72-fold in comparison with that of the susceptible strain.
The rice stem borer, Chilo suppressalis (Walker), is an important rice pest in China, and has evolved resistance to several classes of insecticides. Flubendiamide is a phthalic diamide insecticide that shows selective insecticidal activity against lepidopterous insects. The susceptibility of 40 field populations of C. suppressalis, collected in 2011 and 2012 in seven provinces of south-eastern China, to flubendiamide was determined through rice seedling dipping bioassay method. Of these 40 populations, seven populations that were seldom exposed to flubendiamide were used to set up the baseline sensitivity, and the LC50 value was 0.092 mg/L. Variation in susceptibility among the 40 field populations was high (34-fold). The range of mean lethal concentration (LC50) values in response to this chemical was between 0.032 mg/L (FS11) and 1.090 mg/L (JH12) across the populations. Substantial variations of the susceptibility to flubendiamide were detected among different geographic populations. There was no significant difference observed between years for most populations, except for populations from Jinhua and Lujiang. Resistance ratios to the chemical ranged from 0.8 to 11.8, indicating that most colonies remained susceptible or showed certain decrease in susceptibility. It was found that 16 of the 40 populations had some level of resistance. However, moderate level of resistance was discovered in only one population from JH12 from Zhejiang province (11.8-fold). Other 15 populations showed low level of resistance (5.1–9.3-fold) to flubendiamide. These data are useful in future monitoring programs for detecting any changes in susceptibility as a result of using flubendiamide.
Bactrocera tau (Walker), a major invasive pest worldwide, was first described in Fujian (China) in 1849 and has dispersed to tropical and subtropical Asia and the South Pacific region. Few data are available on its colonization history and expansion processes. This pilot study attempted to reconstruct the colonization history and pathways of this pest in China and neighboring Southeast Asian countries based on mitochondrial DNA. Results of the study showed six genetic groups corresponding to geographical characteristics, although the pattern was relatively weak. Homogeneous genetic patterns were observed within southern and central China, and northern Vietnam. Continuous colonization from the coast of southern China to inland regions of China and northern Vietnam was suggested. Strong genetic structure was observed in western China, Thailand, and Laos. The isolation of four of the six groups was most probably attributable to major topographical barriers of western China. Yunnan acted as a contact zone of B. tau in China and neighboring Southeast Asia. The absence of isolation by distance and the overall low phylogeographic structure of B. tau suggested that long distance dispersal events and human activities could play a major role in the colonization and expansion patterns of B. tau. By analyzing the genetic diversity, gene flow, haplotype phylogeny, and demographic history of 23 fly populations,wehypothesized that B. tau could have been introduced long ago in southern China, from which it further expanded or that southern China could correspond to the native range of this species.
Changes in temperature can result in fundamental changes in plant physiology. This study investigated the impact of different temperatures from 14 to 26°C on the resistance or susceptibility to the Hessian fly, Mayetiola destructor (Say), of selected wheat cultivars that are either currently popular in the Great Plains area or soon to be released to this region. We found that many wheat cultivars including ‘Bill Brown,’ ‘Byrd,’ ‘Endurance,’ ‘Fuller,’ ‘GA-031257-10LE34,’ and ‘KS09H19-2-3’ were susceptible to Hessian fly infestation at ≥20°C, but became resistant at a certain lower temperature, depending on different cultivars. These cultivars were classified as Hessian fly susceptible according to the traditional standards, and their impact on Hessian fly management needs to be reevaluated. However, many wheat cultivars that were resistant at ≤20°C became destabilized at a certain higher temperature. Phenotypic variations among the resistant cultivars at different temperatures were also observed, suggesting potential different resistance mechanisms. Studies on the genetic and molecular mechanisms associated with resistance at different temperatures are needed, which may lead to improved wheat cultivars with more durable resistance to Hessian fly infestation.
Eight biotypes of the Russian wheat aphid, Diuraphis noxia (Kurdjumov), have been discovered in the United States since 2003. Biotypes are identified by the distinct feeding damage responses they produce on wheat carrying different Russian wheat aphid resistance genes, namely, from Dn1 to Dn9. Each Russian wheat aphid biotype has been named using plant damage criteria and virulence categories that have varied between studies. The study was initiated to compare the plant damage caused by all the eight known Russian wheat aphid biotypes, and analyze the results to determine how Russian wheat aphid virulence should be classified. Each Russian wheat aphid biotype was evaluated on 16 resistant or susceptible cereal genotypes. Plant damage criteria included leaf roll, leaf chlorosis, and plant height. The distribution of chlorosis ratings followed a bimodal pattern indicating two categories of plant responses, resistant or susceptible. Correlations were significant between chlorosis ratings and leaf roll (r2 = 0.72) and between chlorosis ratings and plant height (r2 = 0.48). The response of 16 cereal genotypes to feeding by eight Russian wheat aphid biotypes found RWA1, RWA2, RWA6, and RWA8 to differ in virulence, while Russian wheat aphid biotypes RWA3, RWA4, RWA5, and RWA7 produced similar virulence profiles. These biotypes have accordingly been consolidated to what is hereafter referred to as RWA3/7. Our results indicated that the five main biotypes RWA1, RWA2, RWA3/7, RWA6, and RWA8 can be identified using only four wheat genotypes containing Dn3, Dn4, Dn6, and Dn9.
Experiments were performed to determine the efficacy of a single aerosol application of the insecticides methoprene and piperonyl butoxide-synergized pyrethrin, alone or in combination, and the insecticide carrier, Isopar M, against Tribolium castaneum (Herbst), the red flour beetle. The initial test exposed adults to insecticide treatments and placed male/female pairs in flour. All adults exposed to synergized pyrethrin were knocked down for at least 24 h after exposure but they recovered. High adult survival and similar average numbers of living F1 progeny were produced regardless of treatment exposure. In a separate test, insecticide treatments were directly applied to newly laid eggs, which resulted in the suppression of egg hatch. Synergized pyrethrin was the most effective insecticide (P ≤ 0.001) for suppressing egg hatch. The effect of flour on insecticide activity to eggs and consequent insect development was also evaluated. An amount of 0.01 g of flour in the exposure arena, 62-cm2 area, was not sufficient for individuals to develop beyond the early larval stages, regardless of the treatment. As the flour amount in the arena increased from 1 to 5 g, the number of eggs that could develop to the adult stage increased, but this number was significantly lower in the insecticide treatments than in the control or carrier treatments. The results of the later tests indicate a high efficacy of the insecticides alone or in combination on T. castaneum egg hatch and development to the adult stage.
The invasive spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), has become a serious pest in the United States. Identification of immature and poorly preserved specimens can be difficult. A molecular diagnostic method for distinguishing D. suzukii from other Drosophila spp. associated with fruit in the United States was developed. A 709-bp region of the mitochondrial DNA cytochrome oxidase I gene was amplified from D. suzukii collections in the United States and compared with sequences of other Drosophila taxa from GenBank. Based on DNA sequence polymorphisms, a polymerase chain reaction—restriction fragment length polymorphism analysis using the restriction enzyme Msp-I was found to differentiate D. suzukii from other Drosophila spp. in the United States. This technique can identify field-collected specimens from various sources and specimens regardless of life stage. This molecular diagnostic method will be useful for monitoring the spread of this economically important invasive insect.
Current detection tools for Sirex noctilio F. (Hymenoptera: Siricidae) in North America are poor. To determine the importance of intercept trap type for capturing females of S. noctilio and its native congener, Sirex nigricornis F., in eastern North America, we report on seven trap comparison studies from different years and geographic locations. Among studies, total numbers of S. noctilio captured were low (mean of ≤1 wasp per trap). Total numbers of S. nigricornis caught were generally greater, and ranged from a mean of 1–13 wasps per trap. Nearly all studies found no significant differences among intercept trap types in the number of woodwasps caught. For future studies, we recommend that either panel or 12-unit Lindgren funnel traps be used to catch S. noctilio or S. nigricornis in eastern North America.
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