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Cover crops can be planted in rotation with cash crops to improve soils, assist in weed growth prevention, and help suppress plant pathogenic nematode populations. Experiments were conducted in northern and north-central Florida to evaluate bee populations within cover crop plants, including sunn hemp (Crotalaria juncea L.), sorghum-sudangrass (Sorghum bicolor [L.] Moench × S. bicolor var. sudanense [Piper] Stapf.), and cowpea (Vigna unguiculata [L.] Walp.). Almost 150 bees in 10 species and over 700 bees in 15 species were collected in pan (bee bowls) and blue vane traps, respectively. Both sets of traps captured bees from within all cover crop plots, indicating that these bees forage in disturbed habitats. The dominant bees collected, Melissodes spp., are ground-nesting solitary bees which may have been utilizing the ground below the plants and the border plot areas as a nesting site. Only a subset of the species composition associated with the cover crops was relevant to the pollination of sunn hemp, which requires large-bodied bees such as species of Xylocopa and Megachile.
Postharvest almond moth (Cadra cautella Walker; Lepidoptera: Pyralidae) infestation is one of the primary challenges for production of dates, Phoenix dactylifera L. (Arecaceae) cv. ‘Khodari.’ This study was a simulation of early almond moth infestations in uncontrolled storage conditions. It aimed to investigate the effects of low level almond moth infestations on the population growth of the moth, the damage to the dates, bacterial and fungal contamination, and the nutritional value of the dates. One, 2, and 3 pairs of male and female moths were introduced into 250 g Khodari date samples. Noninfested dates were used as controls. Each treatment was performed in 10 replicates. The results showed a more than 25-fold increase in the almond moth population and significant damage to the dates. The moth population in the 2 pair treatment was the highest. Moth infestation also increased microbial contamination by more than 3-fold compared with noninfested dates. The treatment of the 3 pairs of moths significantly increased the bacterial load more than 20-fold when compared to the control. The fungal contamination in the 2 and 3 pair treatments were more than 5-fold higher than that of the control. In contrast, the moth pairs did not significantly affect the sugar, protein, fiber, ash, or water contents of dates. The results suggest that infestation by a single pair of almond moths at the initial stage postharvest causes significant damage and contamination in Khodari dates.
Climate change impacts the current and potential distribution of many insects, since temperature is often a limiting factor to where the insects can survive. The Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), has never been reported in South Korea despite its close proximity to 2 countries (China and Japan) where this economically important pest has been reported. This may be due to the average winter temperature in South Korea which is below 4 °C, the lower limit of the current distribution range of Formosan subterranean termite. However, with climate change leading to increased temperatures, South Korea may be susceptible to successful invasion by Formosan subterranean termite. The objective of this study is to estimate the future possible distribution of Formosan subterranean termite in Korea based on temperature. Climate data from Korea showed a significant increase of 2.19 °C per 100 yr in average annual temperature from 1910 to 2018. Previous and current average winter temperatures were higher than 4 °C only in Jeju, and most provinces did not exceed 4 °C, except for some southern cities such as Busan in 2000 to 2019. With the estimated rate of temperature rises, winter temperatures in Gyeongsangnam-do will exceed 4 °C starting from 2020, and Jeollanam-do will exceed 4 °C from 2060. Coupled with the statistically significant, increased annual trade between Korea and other countries (China, Japan, Taiwan, and the USA) where C. formosanus is currently distributed, we predict that Formosan subterranean termite will become established in South Korea, probably starting from a southern trade port such as Busan.
The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephrtitidae), and the Chinese citrus fly, Bactrocera minax (Enderlein) (Diptera: Tephritidae), are 2 destructive citrus fruit pests in China. A field study was conducted during Sep to Oct of 2018 in Dongkou County of Hunan Province to assess (1) fruit infestations at the time of harvest under 2 management levels, and (2) the efficacy of culling at harvest (i.e., visual inspection and removal of the infested fruits) on reducing the number of infested fruits. A total of 26,400 fruits of Satsuma mandarins, Citrus unshiu (Swingle) Marcov (Rutaceae), were harvested from 2 groves with 1 representing highly managed groves, and the other representing commonly managed groves (low management). Fruit culling was conducted immediately to separate fruits into 5 groups: (1) B. minax infested fruits, (2) B. dorsalis infested fruits, (3) B. minax + B. dorsalis infested fruits, (4) suspected fruit fly infested fruits, and (5) fruit fly free fruits. Fruit dissection was conducted 4 wk later to determine the actual number of the infested fruits, and also to act as a check on the accuracy of visual inspection on the reduction of the number of infested fruits. The highly managed grove had 0.02% infested fruits vs. 2.19% in the low managed grove, a 99.09% reduction in infestation rate. Culling reduced the infested rate to 0.0077% in the highly managed grove and 1.14% in the low managed grove, a reduction of 62% and 48%, respectively, compared to that before culling. About 99% and 73% of fruits which were identified as infested actually were pest free in the 2 groves, respectively. The result of this study suggests that field management is highly effective and critical in reducing fruit fly infestation. The efficacy of culling at harvest on reducing the number of infested fruits was moderate. The accuracy of using culling for identifying the infested fruits was unreliable.
Since 1987, as many as 16 southeastern US states participate in a 4 wk annual spring Dendroctonus frontalis (Zimmerman) (Coleoptera: Curculionidae) trapping survey. The purpose of the survey is to assess the current D. frontalis outbreak potential, and anticipate prevention and suppression needs for the coming yr. This prediction system relies on capturing the peak D. frontalis spring dispersal, thus timing of trap deployment is crucial. Forest managers traditionally attempt to deploy traps at the onset of flowering dogwood (Cornus florida L.; Cornaceae) bloom, which is commonly assumed to coincide with peak D. frontalis spring dispersal. The objective of this study is to examine the validity of dogwood bloom as an indicator of peak D. frontalis spring dispersal. Yr-round trapping data in 2014 and 2015 from Mississippi and Florida were used to identify peak D. frontalis and Thanasimus dubius (Fabricius) (Coleoptera: Cleridae) dispersal periods. Peak D. frontalis dispersal then was compared with dogwood blooming dates from the USA National Phenology Network and personal records. Then, both dogwood bloom dates and peak D. frontalis dispersal were compared with timing of actual historic state D. frontalis trapping efforts. We also compared peak D. frontalis dispersal with T. dubius peak dispersal, because T. dubius trap captures are used in the prediction model. Last, we examined the utility of extending the spring survey to 6 wk by comparing the 4 wk peak D. frontalis trap captures with a corresponding 6 wk peak. On average, mean onset of dogwood bloom occurred 3 wk after the peak 4 wk period of D. frontalis flight activity. The average T. dubius peak dispersal occurred 1.5 wk after peak D. frontalis dispersal. The 6 wk extension provided only a 12% overall average increase in D. frontalis trap captures. Eastern redbud (Cercis canadensis L.; Fabaceae) also had been suggested as a replacement trap deployment cue; therefore, eastern redbud and flowering dogwood blooming dates in 2019 were monitored on a Mississippi State University property in Oktibbeha County, Mississippi, USA. On this site eastern redbud trees bloomed on average 2.3 wk before the average bloom date of flowering dogwood trees.
Francelina Aparecida Duarte Rocha, Yaremis Beatriz Meriño-Cabrera, Eliseu José Guedes Pereira, José Cola Zanuncio, Wellington Garcia Campos, José Eduardo Serrão, Maria Goreti Almeida Oliveira
Spodoptera cosmioides Walker and Spodoptera eridania Stoll (both Lepidoptera: Noctuidae) are herbivorous insects affecting crop yield. Understanding midgut digestive enzyme properties in these caterpillars when feeding on different resources is important for control strategies of these agricultural pests. This study evaluated the activity of midgut digestive enzyme total proteases, trypsin, cysteine proteases, and chymotrypsin in S. cosmioides and S. eridania feeding on natural soybean and cotton leaves and artificial diets. The proteolytic activities of midgut digestive enzymes in S. cosmioides and S. eridania vary according to diet, suggesting adaptation of these caterpillars to different host plants in order to avoid the inhibitory effects of secondary metabolites through the overexpression of proteases. High activities occur for trypsin and total proteases in both insects indicating that these enzymes are potential targets for inhibition in pest control programs.
In turfgrass systems, nematicides are a valuable tool for managing plant-parasitic nematode populations, but few studies have examined non-target nematicide effects on arthropods. Our study evaluated effects of turfgrass nematicide formulations of abamectin (Divanem SC), fluopyram (Indemnify), furfural (MultiGuard Protect EC), and fluensulfone (Nimitz Pro G) on arthropod populations in bermudagrass (Cynodon spp.; Poaceae). A randomized block design was used with 5 replications of the 4 nematicide treatments and an untreated control. Plots were 6 m2 with 0.6 m untreated borders between adjacent plots. Data were collected from 1.5 m2 subplots located in the center of the treatment plots. Nematicides were applied at labeled rates every 4 wk as a summer treatment program from 7 Jun to 30 Aug 2016 and from 24 Apr to 18 Jul 2017 at the University of Florida Plant Science Research and Education Unit in Citra, Florida, USA. Samples were collected before treatment and at 2 d, 14 d, 56 d, and 238 d after the final treatment. Data from each nematicide treatment were compared to the untreated data at each sample date using analysis of covariance with initial population counts serving as the covariate. Abamectin treatments significantly increased fungivore mite abundance relative to the untreated control at 2 sampling dates in 2016 and 3 sampling dates in 2017. Abamectin also decreased collembolan abundance significantly at 2 sampling dates in 2017. Fluopyram increased predatory mite abundance significantly at 3 sampling dates in 2016; decreased collembolan abundance significantly at 4 sampling dates in 2017; and significantly increased phytophagous insect abundance at 2 dates in 2017. Furfural and fluensulfone had low impacts on arthropod abundance. The results of this study suggest nematicides can impact arthropods in bermudagrass, which could affect organic matter decomposition and nutrient cycling processes.
Wolbachia Hertig and Wolbach (Rickettsiales: Anaplasmataceae) are non-culturable, bacterial endosymbionts that have been found in a broad range of arthropods and other invertebrate species. They have been implicated in human and veterinary pathologies, and may play a major role in embryonic development and evolution of host species. Given the apparent ubiquity of Wolbachia in certain animal taxa suggested by previous studies, there are still many unanswered questions about its biology. Like other obligate intracellular bacteria, they are difficult to cultivate outside of their host and often are analyzed using molecular methods. Polymerase chain reaction (PCR) assays have been developed previously for Wolbachia detection within host species, and several genes have been explored for strain typing and phylogenetic reconstruction. However, given the expansive host range and biological complexity of symbiotic relationships between Wolbachia and its host species, new methods could help accelerate the pace of Wolbachia research. As part of an overarching goal to study the distribution of Wolbachia in local mosquitoes and in the heartworm, Dirofilaria immitis (Leidy) (Rhabditida: Onchocercidae), we aimed to develop cost-effective methods that can be used in strain identification and analysis. We developed a novel PCR assay targeting the gyrA gene of Wolbachia and explored various methods of sample preparation. Presumptive Wolbachia were detected in mosquito specimens from several genera, as well as from D. immitis samples obtained from canine necropsy. DNA sequence analysis of the PCR products confirmed the identity of Wolbachia and revealed variability within some regions of the gyrA gene that correspond to host species. Consequently, this gene could be useful for future phylogenetic and population studies.
Reynaldo Millán-Chaidez, José Antonio Garzón-Tiznado, Perla Judith Linares-Flores, Sixto Velarde-Félix, Gabriel Antonio Lugo-García, Jesús Enrique Retes-Manjarrez
Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Mediterranean (Q biotype) is a major pest of tomato (Solanum lycopersicum L.; Solanaceae) globally. To our knowledge, no whitefly resistant cultivar has been released commercially, and breeding programs are hampered by the lack of resistance sources to this insect which are related closely to the cultivated tomato. Two non-free-choice experiments on B. tabaci with 22 landrace (S. lycopersicum) and wild tomato (S. lycopersicum var. ‘cerasiforme') populations from Mexico were performed to find sources of antibiosis resistance to this insect. Plants were infested with 20 insects per 1 leaflet of each plant using plastic micro-cages. In both assays, the number of adults and eggs were counted at 4 d post infestation, the number of nymphs (12 d post infestation), new adults, and non-glandular trichomes at 28 d post infestation. The highest B. tabaci resistance was detected in the UTC-SV13 population followed by UTC-SV12, UTC-SV1, and UTC-SV3 with a range of 15.0 to 20.0 dead adults, 0.0 to 16.5 eggs, 0.0 to 12.6 nymphs, 0.0 to 9.7 new adults per leaflet, and with a reproduction index of 0.0 to 21.7. Ten populations showed an intermediate level of resistance significantly lower in the number of dead adults, eggs, nymphs, new adults, and reproduction index compared to the commercial cultivar (‘Bonny Best') used as the standard. The remaining 8 genotypes and the commercial cultivar were fully susceptible to B. tabaci. The number of non-glandular trichomes correlated significantly with the number of eggs, nymphs, and new adults emerging from the infested plants, suggesting that the density of non-glandular trichomes is favorable for whitefly reproduction. Those genotypes with moderate to high levels of resistance to B. tabaci are potential candidates for developing commercial tomato cultivars with some resistance levels to this insect.
Methionine is a naturally occurring amino acid that has demonstrated toxic properties for control of larval mosquitoes in laboratory experiments. Methionine offers many desirable qualities for an effective, biorational pesticide, including its minimal effects on non-target species. Because previous studies regarding this amino acid's toxicity were laboratory based, the next step is to establish if methionine is likely to have similar effects in natural water bodies before attempting costly field trials. Therefore, the goal of this study was to test the effectiveness of DL-methionine applied to various water sources. Concentration response experiments conducted in glass jars used larval Aedes aegypti (L.) (Diptera: Culicidae) as a model organism. Well, deionized, and pond water were evaluated in the study. In general, increased mortality of Ae. aegypti larvae occurred with increasing concentrations of DL-methionine at 48 h. However, larval DL-methionine LC50 values were not different between water sources. This study has shown that DL-methionine can be added to various water sources as a possible biorational larvicide when applied to natural water sources such as ponds or water-holding containers that often are preferred larval developmental sites for a variety of mosquito disease vectors.
The nutritional properties of subterranean termite exuviae (shed exoskeletons) are not well-known because obtaining the large quantities necessary for investigation is difficult. A method for collecting large numbers of exuviae is reported here for the Asian subterranean termite, Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae), an invasive and economically important tropical termite species. In this study, groups of 1,000 C. gestroi workers from 4-yr-old laboratory colonies (n = 3) were allowed to feed on a media pad dyed with Nile Blue A for 2 d. Approximately 16% of the original 1,000 workers did not uptake dye. These individuals were then placed into a Petri dish with dyed filter paper and checked hourly (10:00 A.M. to 10:00 P.M.) for 7 d. Newly molted workers and those individuals that started turning blue were removed to prevent feeding on exuviae. An average of 14 workers molted per d that yielded an average of 12 exuviae with an overall mean of 86 exuviae collected over the 7 d study period. We also found the number of individuals that acquired dye during the study significantly decreased by d. However, variables such as the number of exuviae, newly molted individuals, and cadavers were not correlated with d of collection because termites molt asynchronously.
The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a key pest of sweet pepper cultivation, where it causes feeding damage, excretes phytotoxic substances, and transmits important viruses. Control with chemical insecticides often is ineffective because endophytic oviposition and the cryptic habits of the pest provide protection. In Uruguay, the biological control program of this pest in sweet pepper crops is at risk due to the low settlement rate and high dispersal of releases of predator Orius insidiosus (Say) (Hemiptera: Anthocoridae). Previous studies have ruled out an antibiosis effect as the cause of dispersal; therefore, we hypothesized antixenosis (non-preference) for the sweet pepper plants as the cause of poor biological control by O. insidiosus. The effect of olfactory stimuli from different structures of strawberry, corn, and sweet pepper plants (lamuyo and blocky type) on the behavior of O. insidiosus was evaluated in olfactometry and free-choice cage experiments. Since Orius tristicolor (White) (Hemiptera: Anthocoridae) occurs naturally in the area, it was included also in the study with the aim of assessing whether there are differences in behavior between the species. Orius tristicolor may act as a complementary biocontrol agent or competitor on sweet pepper. Y-tube experiments showed no preference for plant volatiles in any combination, and response to volatile stimuli generally was poor. However, in the free-choice cage experiment, females of both species of Orius preferred the flowering strawberry plants over the flowering sweet pepper plants, which could explain the low establishment of O. insidiosus when released on pepper with neighboring strawberry fields. Given that horticultural greenhouses in Uruguay and in many other countries are open, this information can be very useful in designing the spatial and temporal management of different crops on a production field, which enhances the effectiveness of these predatory species.
A thorough understanding of the local mosquito fauna is required to develop effective mosquito abatement programs and assess risk of arbovirus transmission in an area. Although many mosquito control districts routinely survey adult populations of mosquitoes, few studies address trap bias, attractant bias, and the sampling effort needed to fully describe mosquito community diversity. Quantifying and visualizing differences in mosquito community composition and abundance, collected in adjacent mosquito control districts that use different attractants, provides a first step toward understanding and communicating cross-district arbovirus risk in continuous geographic areas. We obtained female mosquito collection data from CDC (Centres for Disease Control and Prevention) suction light traps from St. Johns County (baited with octenol) and Duval County (baited with dry ice) in Florida, USA, presenting a unique opportunity to summarize and compare collections across 2 attractants in adjacent Florida mosquito control programs. In the current work, we describe the seasonal distribution of mosquito species, highlight proportions of vector species of importance, quantify and assess diversity, and summarize the variation explained by attractant type using partial redundancy analysis. Numerous actual and potential vector species of importance were abundant throughout the sampling period that included Aedes atlanticus (Dyar & Knab), Anopheles crucians Weidemann, Culex erraticus (Dyar & Knab), and Culex nigripalpus Theobald (all Diptera: Culicidae). Dry ice collections yielded the greatest diversity of species with the least trapping effort. Traps baited with octenol yielded the greatest number of mosquitoes with a greater proportion of vector species. The results of the partial redundancy analysis revealed that attractant explained a significant proportion of the variance in the data set. But a significant linear trend also was present indicating that additional spatially structured variables were responsible for a large proportion of the variance in the data. It is necessary to know the differences between mosquito species and trap numbers when varying collection methods and attractants are used to assess arbovirus transmission risk across mosquito control district administrative boundaries. This information can be used to provide more robust and comprehensive surveillance information capable of identifying new challenges to public health safety.
Plant derived volatiles are cues used widely that guide the behavior of plant associated insects, influencing both the ability of insects to locate host plants, as well as tritrophic interactions with predators or parasitoids. Therefore, an understanding of how volatiles impact a specific ecological system may aid the development of plants that are less attractive to pests or more amenable to biocontrol. Because each plant-insect interaction is different, it is important to develop bioassays to compare plants with different volatile profiles and assess their comparative attractiveness to specific insects. To this end, we developed a laboratory-based pair-wise choice assay to determine the oviposition preference of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), a global crop pest, to maize, Zea mays L. (Poaceae) plants with different volatile profiles. An alternative greenhouse-based assay also was developed to assess the effect of different Z. mays plants on the oviposition behavior of Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae), a parasitoid wasp that can be used as a biocontrol agent for S. frugiperda. These bioassays are easily adaptable for use on a range of plant-insect interactions.
This article is the first report on the phytophagous activity of C. hesperidum on hemp plants grown in greenhouses in Kentucky, USA. Hemp plants were grown in a greenhouse where ornamental plant species were previously grown but were not present at the same time. Coccus hesperidum may have been carried by wind because greenhouse windows were kept open. Coccus hesperidum successfully fed and reproduced on the stems and leaves of hemp. After 2 wk a single plant, kept in laboratory for further studies, died as a consequence of the feeding damage caused by a large population of scales. As hemp is expanding to different production areas, C. hesperidum might be a potential pest for hemp grown in greenhouses. The surveillance and early detection of C. hesperidum will contribute to the production of healthy hemp plants to be planted in open fields, especially in southern states of the USA.
Detection of invasive populations of Bactrocera dorsalis relies on traps baited with the male-specific attractant methyl eugenol. Standard protocol involves applying 5 mL of liquid methyl eugenol (1% naled) to a cotton wick, which is then placed inside a Jackson trap. Because of the lure's high volatility, the lure is replaced every 6 wk. Prolonging the lure's longevity would increase trap servicing intervals and reduce associated costs. Conducted at 2 sites in Hawaii, the present study investigated the performance of weathered solid dispensers containing 3, 6, or 10 g of methyl eugenol, deployed with solid insecticidal strips, relative to freshly baited liquid-bearing cotton wicks. At the cooler site, the solid lure/toxicant combination captured as many males as the fresh liquid formulation for as long as 12 wk. At the warmer site, the solid lure/toxicant system had shorter longevity, apparently owing to the reduced effectiveness of the insecticidal strip over time.
Though once considered extinct in Florida, the Eumaeus atala butterfly (Poey) (Lepidoptera: Lycaenidae) has made a slow but steady recovery thanks to grassroots conservation efforts targeting the butterfly and its only native foodplant, the cycad Zamia integrifolia L.f. (Cycadales: Zamiaceae). A robust E. atala population occurs at the Montgomery Botanical Center, a research and conservation facility in Coral Gables, Florida, USA, that cultivates a living collection of global cycads, many of which are critically endangered in the wild. Since the early 2000s, the E. atala population at the Montgomery Botanical Center has grown and adopted an expanded host range, much to the detriment of the plants; both native and exotic cycads incur consistent and severe damage from larval herbivory. This presents a complex situation in which in situ butterfly conservation conflicts with ex situ cycad conservation. Here we describe the local population of E. atala at the Montgomery Botanical Center, suggest testable hypotheses for explaining the butterfly's localized abundance, and discuss implications for butterfly and cycad conservation efforts in Florida.
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