Spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), was monitored from 2010 to 2014 in 314–828 sites located in interior fruit-growing regions of OR and WA, United States, and BC, Canada, using traps baited with apple cider vinegar or sugar-water-yeast. Seasonal population dynamics and sex ratios were summarized for berry, cherry, stone fruit, grape, non-crop host plants, non-host sites, and for conventional IPM, certified organic, backyard, and feral sites, by region and year. Overwintering was detected in all regions and years, despite winter temperatures below -17°C. A spatial analysis was conducted using a Geographic Information System (GIS), daily weather data, geomorphometric measures of terrain, distance to water, and other variables, at each site. Overwintering success at a site, measured as Julian week of first capture of D. suzukii, was significantly related (R² = 0.49) in cherry habitats to year, agronomic treatment, and number of winter days with temperatures >-5°C. In berry, cherry, stone fruit and grape habitats, 2011–2014, it was significantly related (R² = 0.42) to year, agronomic treatment, the logarithm of peak population of D. suzukii in the prior autumn, latitude, elevation, and topographic wetness index. The results show that D. suzukii has adapted to exploit a succession of irrigated crops and feral habitats in mixed landscapes of a semi-arid region with cold winters and hot dry summers, and are shaping strategies for pest management and for biological control.

Modeling can be used to characterize the effects of environmental drivers and biotic factors on the phenology of arthropod pests. From a biological control perspective, population dynamics models may provide insights as to when the most vulnerable pest life stages are available for natural enemies to attack. Analyses presented here used temperature and habitat dependent, instar-specific, discrete models to investigate the population dynamics of Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). This pest is the target of a classical biological control program with the parasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae). The population trends of D. citri eggs, nymphs, and adults, citrus flush growth patterns, and T. radiata activity were monitored monthly on orange and lemon trees at 10 urban sites in southern California for a 2-yr period. Cumulative D. citri egg, nymph, and adult days recorded at each site, were regressed against accumulated degree-days (DDs) to model the population dynamics of each development stage in relation to temperature. Using a biofix point of 1 January, the model predicted that 10% and 90% of eggs were laid by 198 and 2,255 DD, respectively. Populations of small and large D. citri nymphs increased slowly with 90% of the population recorded by 2,389 and 2,436 DD, respectively. D. citri adults were present year round with 10 and 90% of the population recorded by 95 and 2,687 DD, respectively. The potential implications of using DD models for optimizing inoculative releases of natural enemies, such as T. radiata into citrus habitat infested with D. citri, are discussed.

Population dynamics of rusty grain beetle, Cryptolestes ferrugineus (Stephens; Coleoptera: Cucujidae), was studied using different sizes of grain bulks (patches) at various temperatures. The temperatures were 21, 25, 30, 35°C, T-decrease (30°C in the first 4 wk and then decreased 1°C /wk), and T-increase (21°C in the first 2 wk and then increased 1°C /wk). Number of adults and offspring and infested wheat kernels were counted every 4 wk up to 24 wk (31 wk for the T-decrease). The grain bulk patches used were: small (50 ml inner volume, 0.03 kg wheat), medium (2.6 liters inner volume, 2 kg wheat), and large (18 liters inner volume, 14 kg wheat). All of the correlation coefficients between the insect numbers and kernel infestation percentage were ≥0.63. Two types of the population dynamic curves were observed: insect number or density continually increased with time during the entire experiment, or there was a rise then a fall in insect number or density over time, giving a peak number or density. The peak insect density was approximately 400 to 500 adults/kg of wheat for all patches at 30°C or lower. At 35°C, the peak densities of live adults were 3,956 ± 630, 2,094 ± 34, and 1,003 ± 70 adults/kg of wheat in small, medium, and large patches, respectively. Patch size influenced insect population dynamics at 35°C. Insect number inside large patch was more dependent on the previous insect number than that inside small patches.

Data collected in Part I of this study were further analyzed by using mathematical modeling methods. Out of the nine unstructured population models tested, no model could fit the insect numbers under all of the tested conditions. This analysis showed that Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) inside small patches (50 ml volume) had different characterization of population dynamics from that inside large patches (18 liter volume) and had different population demography when the insect number at the previous time was different.The key factor analysis showed that the first two main factors influencing the population dynamics were the temperature and the previous insect numbers.The total numbers of insects increased with the increase of sum of degree days. However, the degree day model developed based on the constant temperatures could not predict insect numbers under fluctuating temperatures. A newly developed model, which used the result of the unstructured population models, key factor analysis, and the degree day model, could explain about 66% of the insect numbers under fluctuating temperature conditions.

Pantala flavescens (Fabricius 1798) (Odonata: Libellulidae) is one of the most common species of migratory dragonflies. P. flavescens adults were captured by a searchlight trap on Beihuang Island (BH Island; 38°24′N, 120°55′E) from 2003 to 2016, where there is no freshwater. This inspired our research to analyze the pattern of seasonal migration and population dynamics. Stable hydrogen isotope measurement and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) were used to simulate the migration pathway of P. flavescens between different breeding habitats. The results showed that there was no significant difference among population numbers of this overseas migration across years (F_{13, 2161} = 0.85, P = 0.604); however, the numbers were significantly different across months (F_{5, 2161} = 3.91, P = 0.003). Our geospatial natal assignment model suggested that P. flavescens trapped on BH were originated in different geographical regions and might have three movement strategies: wandering around northern China and north-bound (positive) and south-bound (negative) movements. Among them, the majority were engaged in wandering around northern China. Model simulations suggested that P. flavescens toured around BH. The results contribute to the knowledge of P. flavescens population ecology in a large-scale geographic region and will aid in the prediction and interpretation of insect migration patterns in response to climate change.

Pierce's disease of grapevine and almond leaf scorch disease are both caused by the bacterial pathogen Xylella fastidiosa Wells et al. In the Central Valley of California, Draeculacephala minerva Ball (Hemiptera: Cicadellidae) is the most common vector of X. fastidiosa. As alfalfa fields and pastures are considered source habitats for D. minerva, it is recommended that almond orchards and vineyards should be distanced from alfalfa and pastures. Here, risk of alfalfa and pastures serving as sources of D. minerva was compared to the potential benefit of alfalfa and pastures serving as sources of generalist natural enemies belonging to the families Chrysopidae and Coccinellidae. Populations of D. minerva were greatest in pastures, whereas chrysopids were least abundant in pastures, and coccinellids were only moderately more abundant in pastures than in vineyards or almond orchards. Accordingly, risk of pastures serving as a source of D. minerva was not offset by any potential benefit of pastures serving as a source of chrysopids or coccinellids. Abundance of D. minerva in alfalfa was low, whereas abundance of chrysopids and coccinellids in alfalfa was high. Thus, well-maintained alfalfa fields were a minor source of D. minerva that may contribute chrysopids and coccinellids to surrounding habitats. Spissistilus festinus (Say) (Hemiptera: Membracidae), a recently identified vector of grapevine red blotch virus, was abundant in alfalfa fields and was observed in vineyards. Thus, a full evaluation of the risk of planting vineyards near alfalfa may require considering risk associated with movement of S. festinus.

Leafhoppers constitute one of the largest groups of pests causing damage to crops worldwide. Edge grasses, which are border crops (also known as border grasses), contain diverse plant species and maintain large populations of leafhoppers during the tropical dry and wet seasons. However, little is known about the diversity of leafhoppers on these grasses.The objective of this study was to characterize the diversity of leafhoppers on maize and on surrounding border grasses during the dry and wet seasons. Leafhopper adults were collected with a sweep net from border grasses during the dry season, when maize is absent. During the wet, maize-growing season, leafhoppers were collected in both the maize fields and their surrounding edge grasses. A highly diverse (H′ = 1.97 ± 2.03) leafhopper population was seen on the edge grasses during the dry season, and during the wet season, leafhopper diversity was higher in the edge grasses (H′= 1.79 ± 1.72) than in the maize fields themselves (H′= 1.67 ± 1.12).Throughout the wet season, the most abundant leafhopper species in border grasses were Stirellus bicolor (Van Duzee) (Hemiptera: Cicadellidae), Graminella sonora (Ball) (Hemiptera: Cicadellidae), and Balclutha incisa (Matsumura) (Hemiptera: Cicadellidae), whereas Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) was the most abundant species in maize fields. All of these species were from the subfamily Deltocephalinae. Canonical Component Analysis showed that leafhopper abundance of Sibovia compta (Fowler) (Hemiptera: Cicadellidae), Graphocephala aurolineata (Fowler) (Hemiptera: Cicadellidae), D. maidis, and S. bicolor was associated with abiotic factors such as relative humidity, soil moisture, temperature, and pluvial precipitation. Nevertheless, for most leafhopper species, abundances were not significantly correlated with the abiotic variables measured.

Winter cover crop mulches can diversify agricultural habitats and provide a range of benefits for crop production and pest management. Here we report the influence of strip tilled winter cover crop mulches on arthropod abundance in organic vegetable plots. Crookneck squash (Cucurbita pepo L.; Cucurbitales: Cucurbitaceae) was direct seeded into mowed and strip tilled barley (Hordeum vulgare L.; Poales: Poaceae), crimson clover (Trifolium incarnatum L.; Fabales: Fabaceae), a barley + crimson clover mixture, or a no-cover crop control. Arthropods on squash plants were assessed weekly using visual counts. Seed predation was assessed using weed seed arenas. In 2013, mixed species cover crops produced the most ground cover, fewest weeds, and largest squash plants, but herbivore and predator abundance were not correlated with any of those factors. In 2014, mixed species cover crops again produced the most ground cover and fewest weeds, but the largest squash plants were found in no-cover crop control plots, which also had the highest herbivore abundance per plant. Predator and herbivore abundance were positively correlated with squash plant size in 2014. There were no differences in seed predation across treatments. Differences in ground cover biomass and weed presence between the 2 yr may have contributed to differences in squash plant quality and subsequent herbivore abundance between seasons. Results suggest that arthropods on plants responded largely indirectly to cover crops through host plant quality. Results are interpreted in light of overall costs and benefits of cover cropping.

Tree hollows are complex microhabitats in which a variety of abiotic and biotic factors shape the community assembly of saproxylic insects. Detecting non-random species co-occurrence patterns is a fundamental goal in ecology in order to understand the assembly mechanisms of communities. We study association patterns of species of Coleoptera and Diptera (Syrphidae), belonging to different trophic guilds, on 72 tree hollows at a local and regional scale in three protected areas in Mediterranean forests using a fixed–fixed null model. Our matrix-level analysis shows a tendency for segregation in species association (species exclusion) at the regional and site levels. However, the high complexity of tree-hollow habitats, offering different resources for a more or less specialized fauna, makes it difficult to prove competition interactions. Indeed, pairwise analysis shows a dominance of non-random aggregation patterns (species coexistence) at the local and regional levels. Both aggregation and segregation of non-random patterns were more common among species from different trophic guilds than within the same guilds, with predators being a common denominator for a high percentage of the inter-guild pairs. Our results suggest that predation and facilitation interactions, together with habitat segregation, are the main factors shaping tree-hollow assemblages, while competition seems to be less important. We conclude that species interactions take an important part of the process of assemblage structuration and special attention should be paid to ‘ecosystem engineers' and threatened species in the conservation of tree hollow assemblages.

Ant community assembly is driven by many factors including species interactions (e.g., competition, predation, parasitism), habitat filtering (e.g., vegetation differences, microclimate, food and nesting resources), and dispersal. Canopy ant communities, including dominant and twig-nesting ants, are structured by all these different factors, but we know less about the impacts of species interactions and habitat filters acting at the colonization or recruitment stage. We examined occupation of artificial twig nests placed in shade trees in coffee agroecosystems. We asked whether species interactions—aggression from the dominant canopy ant, Azteca sericeasur Longino (Hymenoptera: Formicidae)—or habitat filtering—species of tree where nests were placed or surrounding vegetation—influence colonization, species richness, and community composition of twig-nesting ants. We found 20 species of ants occupying artificial nests. Nest occupation was lower on trees with A. sericeasur, but did not differ depending on tree species or surrounding vegetation. Yet, there were species-specific differences in occupation depending on A. sericeasur presence and tree species. Ant species richness did not vary with A. sericeasur presence or tree species. Community composition varied with A. sericeasur presence and surrounding vegetation. Our results suggest that species interactions with dominant ants are important determinants of colonization and community composition of twig-nesting ants. Habitat filtering at the level of tree species did not have strong effects on twig-nesting ants, but changes in coffee management may contribute to differences in community composition with important implications for ant conservation in agricultural landscapes, as well as biological control of coffee pests.

Coconut plantations are attacked by the lethal yellowing (LY), which is spreading rapidly with extremely destructive effects in several countries. The disease is caused by phytoplasmas that occur in the plant phloem and are transmitted by Haplaxius crudus (Van Duzee) (Auchenorrhyncha: Cixiidae). Owing to their phloem-sap feeding habit, other planthopper species possibly act as vectors. Here, we aimed at assessing the seasonal variation in the Auchenorrhyncha community in six dwarf coconut accessions. Also, we assessed the relative contribution of biotic (coconut accession) and abiotic (rainfall, temperature) in explaining Auchenorrhyncha composition and abundance. The Auchenorrhyncha community was monthly evaluated for 1 yr using yellow sticky traps. Among the most abundant species, Oecleus sp., Balclutha sp., Deltocephalinae sp.2, Deltocephalinae sp.3, Cenchreini sp., Omolicna nigripennis Caldwell (Derbidae), and Cedusa sp. are potential phytoplasma vectors. The composition of the Auchenorrhyncha community differed between dwarf coconut accessions and periods, namely, in March and April (transition from dry to rainy season) and August (transition from rainy to dry season). In these months, Oecleus sp. was predominantly found in the accessions Cameroon Red Dwarf, Malayan Red Dwarf, and Brazilian Red Dwarf Gramame, while Cenchreini sp. and Bolbonota sp. were dominant in the accessions Brazilian Yellow Dwarf Gramame, Malayan Yellow Dwarf, and Brazilian Green Dwarf Jequi. We conclude that dwarf coconut host several Auchenorrhyncha species potential phytoplasma vectors. Furthermore, coconut accessions could be exploited in breeding programs aiming at prevention of LY. However, rainfall followed by accessions mostly explained the composition and abundance of the Auchenorrhyncha community.

Aphids (Hemiptera: Aphididae) can harbor two types of bacterial symbionts. In addition to the obligate endosymbiont Buchnera aphidicolaMunson, Baumann and Kinsey 1991 (Enterobacteriales: Enterobacteriaceae), several facultative symbiotic bacteria, called secondary (S) symbionts, have been identified among many important pest aphid species. To determine interpopulational diversity of S-symbionts, we carried out a survey in a total of 18 populations of six aphid species collected from six localities in Tunisia, by performing a diagnostic polymerase chain reaction analysis of partial 16S–23S rRNA operon sequences. While 61.7% of individuals contained only Buchnera, three S-symbionts were found at different frequencies. Arsenophonus sp. Gherna et al. 1991 (Enterobacteriales: Enterobacteriaceae) was found in all species under study except for Acyrtosiphon pisum (Harris 1776) (Aphidinae: Macrosiphini); Serratia symbiotica Moran et al. 2005 (Enterobacteriales: Enterobacteriaceae) was present in all analyzed individuals of A. pisum but only sporadically in Aphis spiraecola (Patch 1914) (Aphidinae: Aphidini) and Hyalopterus amygdali (Blanchard 1840) (Aphidinae: Aphidini), while Hamiltonella defensa Moran et al. 2005 (Enterobacteriales: Enterobacteriaceae) was found in all analyzed individuals of one population of Aphis gossypii (Glover 1877) (Aphidinae: Aphidini) and sporadically in two populations of Hyalopterus. The lysogenic bacteriophage APSE-1 (A. pisum secondary endosymbiont, type 1) was detected in the three populations infected with H. defensa. This bacteriophage has been associated with moderate protection against braconid parasitoids in pea aphids. The high prevalence of Arsenophonus sp. in our samples is in accordance with previous studies indicating that, among gammaproteobacteria, this genus is one of the most widespread insect facultative symbionts.

The wild cochineal (Dactylopius opuntiae Cockerell) (Hemiptera: Dactylopiidae) is considered to be the most important pest in cactus pear plantations. In Mexico, there are seven natural enemies that provide natural biological control of D. opuntiae. However, their role and impact have not been evaluated. In this article, we report on aspects of the population biology of Chilocorus cacti L. (Coleoptera: Coccinellidae), which is considered one of the main natural enemies of D. opuntiae. We also conducted experiments to evaluate the consumption of C. cacti by this predator when fed nymphs and adult females of D. opuntiae. Changes in the survival function of D. opuntiae in the presence or absence C. cacti were also identified. Both larvae and adults of C. cacti prefer to consume D. opuntiae nymphs because the wax produced by adult females presents a significant obstacle. The survival analysis showed that the presence of C. cacti had significant negative effects on D. opuntiae survival. C. cacti significantly increased its abundance while reducing the density of adult female D. opuntiae, but this impact occurred only after they had consumed the more preferred nymphs. For this reason, natural enemies other than C. cacti may be required to achieve adequate levels of biological control.

Agricultural practices affect arthropod communities and, therefore, have the potential to influence the activities of arthropods. We evaluated the effect of cover crop species and termination timing on the activity of ground-dwelling predatory arthropods in a corn-soybean-wheat rotation in transition to organic production in Pennsylvania, United States. We compared two cover crop treatments: 1) hairy vetch (Vicia villosa Roth) planted together with triticale (×Triticosecale Wittmack) after wheat harvest, and 2) cereal rye (Secale cereale Linnaeus) planted after corn harvest. We terminated the cover crops in the spring with a roller-crimper on three dates (early, middle, and late) based on cover crop phenology and standard practices for cash crop planting in our area. We characterized the ground-dwelling arthropod community using pitfall traps and assessed relative predation using sentinel assays with live greater waxworm larvae (Galleria mellonella Fabricius).The activity density of predatory arthropods was significantly higher in the hairy vetch and triticale treatments than in cereal rye treatments. Hairy vetch and triticale favored the predator groups Araneae, Opiliones, Staphylinidae, and Carabidae. Specific taxa were associated with cover crop condition (e.g., live or dead) and termination dates. Certain variables were positively or negatively associated with the relative predation on sentinel prey, depending on cover crop treatment and stage, including the presence of predatory arthropods and various habitat measurements. Our results suggest that management of a cover crop by roller-crimper at specific times in the growing season affects predator activity density and community composition. Terminating cover crops with a roller-crimper can conserve generalist predators.

The tachinid Nemorilla maculosa Meigen (Diptera: Tachinidae) was introduced from Taiwan to Benin for evaluating its potential as a biocontrol candidate against the cowpea pest Maruca vitrata (Fabricius) (Lepidoptera: Crambidae). To optimize its rearing, we assessed the influence of M. vitrata larval age and rearing substrate—cowpea germinating grains and peabush leaves—on its life table parameters, while its host specificity was investigated with regard to nontarget effects. Parasitism rates were higher when older larvae (10- and 14-d old) were offered to females of N. maculosa compared to the younger (2-, 4-, and 6-d old) host larvae. Regardless of the rearing substrate, development time was longer for females than males, and females lived longer than males irrespective of the age of the host. Sex ratio did not vary significantly with host ages or rearing substrate. The average number of eggs laid by a female reared from M. vitrata larvae feeding on cowpea germinating grains or peabush leaves was 94.2 ± 4.38 and 71.9 ± 1.70 eggs, respectively. The host suitability of N. maculosa was assessed by testing four nontarget Lepidoptera species: Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae), Sesamia calamistis Hampson (Lepidoptera: Noctuidae), Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae), and Eldana saccharina Walker (Lepidoptera: Pyralidae). Larvae of S. littoralis and C. cephalonica were successfully parasitized while N. maculosa did not develop in the larvae of E. saccharina and S. calamistis although they were parasitized. Despite the potential of N. maculosa as a biological control agent against the pod borer M. vitrata, more detailed nontarget studies, extending to other native Crambidae species, are needed before making decisions on field releases.

Pollination services provided by managed bees are essential for California almond (Prunus dulcis Mill.; Rosales: Rosaceae) production. Currently, pollination needs are met by rented or owned Apis mellifera L. (Hymenoptera: Apidae; honey bee) colonies. Excessive demand on a challenged A. mellifera industry to provide strong colonies in early spring has caused sharp increases in rental prices over the past decade, inviting the consideration of alternative pollinators in addition to, or in place of, A. mellifera. Osmia lignaria Say (Hymenoptera: Megachilidae; the blue orchard bee) is an excellent pollinator of fruit and nut trees, but its pollination impacts when used in tandem with A. mellifera have yet to be evaluated in commercial almond orchards. A 2-yr study was conducted in California orchards to compare almond pollination and production using A. mellifera as sole pollinator to an alternative practice of adding O. lignaria as a co-pollinator with A. mellifera. Almond orchard managerial decisions, such as for pesticide use and irrigation intensity, vary between almond growing regions because of local climates. Therefore, both north-central and southern sites of California's San Joaquin Valley are represented. We compared bee visitation, nut set, and nut yield between orchards and between tree rows within orchards. Also, O. lignaria reproductive success was recorded to assure that these bees remained in the orchards as pollinators and to assess the ability to sustain these bees under regional orchard conditions. We demonstrated that augmenting large commercial almond orchards with O. lignaria can significantly increase nut set and sometimes nut yield in both regions evaluated.

In 2015, we conducted a statewide assessment of honey bee exposure to pesticides with assistance of volunteer beekeepers. Pollen trapping was conducted at 32 sites in the spring, summer, and early fall. Apiary locations ranged from unmanaged natural landscapes to managed agricultural or urban landscapes. Pollen samples at each site were aggregated over the collection dates and chemical residue analysis was conducted on each pollen sample for 190 pesticides and metabolites using HPLC/MS. Twenty-five different residues were detected for an average of 2.9 detections per site. Detections were dominated by fungicides, but risk, calculated as: ppb residue concentration/ LD₅₀, was mostly due to insecticides. Beekeeper perceived land-use in the vicinity of each apiary was associated with significant differences in the number of detections and residue concentrations, agricultural landscapes greater than nonagricultural. However, there was no significant difference in oral or contact risk quotients due to land-use type. The landscape composition surrounding apiaries, derived with GIS, determined pesticide exposure for honey bees when total detections, log pesticide residue concentration, and log contact risk quotients were used as measures. Partial least squares explained 43.9% of the variance in pesticide exposure due to landscape composition. The best predictors describing pesticide exposure were: area (ha) of blueberry, coniferous forest, and urban/developed land cover types. Maine is the most forested state in the United States (as determined by % land area forested, 93%) and a negative exponential decay was observed between land area in conifer forest and the number of pesticide detections per apiary.

The resistance of commercial rice (Oryza sativa L.) varieties widely grown in Louisiana was assessed against the rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), the major insect pest of rice in the United States, in a 5-yr field study that included conventional inbred, herbicide-tolerant, and hybrid varieties. Resistance was evaluated by comparing densities of immature rice water weevils (larvae and pupae) in root–soil core samples taken at two time points after flooding. Randomized block experiments were conducted in two different locations to enable identification of potentially resistant varieties over diverse environments. There were small but significant differences in the resistance of commercial varieties over the 5-yr field study. The variety ‘Jefferson’ was found to support larval densities 6–70% lower than other varieties, while ‘Jupiter’ often supported higher larval densities. Greenhouse experiments evaluated adult preference for oviposition and survivorship of larvae on different varieties. Females exhibited limited ovipositional preference for varieties: numbers of weevil eggs per plant differed significantly among varieties in choice tests but not in no-choice tests, while first instar densities in both choice and no-choice tests showed no significant differences among varieties. Analysis of data from both choice and no-choice tests showed that numbers of late instars and pupae differed significantly among varieties, suggesting presence of antibiosis in some cultivars. Our results suggest that none of the varieties tested possess high levels of resistance to rice water weevil infestation, although ‘Jupiter’ appears to be more susceptible than other varieties and ‘Jefferson’ appears to be somewhat more resistant.

Vector-borne plant pathogenic bacteria can induce changes in infected plants favoring the insect vector behavior and biology. The study aimed to determine the effect of maize bushy stunt phytoplasma (MBSP) postinoculation period on the host plant preference and transmission efficiency by the corn leafhopper, Dalbulus maidis DeLong & Wolcott, 1923 (Hemiptera: Cicadellidae). In a series of choice tests, D. maidis preference was measured as settling and oviposition on healthy maize plants versus infected maize plants showing early disease symptoms, advanced symptoms, or no symptoms. Finally, transmission efficiency of D. maidis was measured when the vector previously acquired the phytoplasma from asymptomatic source plants at different postinoculation periods. D. maidis adults preferred to settle and to oviposit on healthy than on symptomatic infected plants with advanced disease symptoms, and preferred asymptomatic plants over symptomatic ones. MBSP transmission by D. maidis was positively correlated with the postinoculation period of the source plant. Results suggest an MBSP modulation for D. maidis preference on asymptomatic infected maize plants in the early stages of the crop, allowing the pathogen an undetected transmission.

Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is an egg parasitoid wasp from East Asia. It is considered to be an important natural enemy of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). Ongoing efforts to evaluate the physiological host range of this potential classical biological control agent have demonstrated that the wasp can parasitize at least 11 genera of nontarget Pentatomoidea in North America in no-choice tests. However, factors such as host-acceptance behavior that might affect nontarget parasitism in the field are poorly understood. We evaluated the preference of T. japonicus females provided with egg clusters of H. halys, Thyanta custator accerra McAtee (Hemiptera: Pentatomidae), Podisus maculiventris (Say) (Hemiptera: Pentatomidae), and Euschistus variolarius (Palisot de Beauvois) (Hemiptera: Pentatomidae) when wasps were reared on the target pest, H. halys, and the nontarget species, T.c. accerra and P. maculiventris. When reared on H. halys, T. japonicus showed a strong preference for H. halys, and frequently rejected nontarget hosts after inspection. When T. japonicus was reared on nontarget hosts, females showed reduced host-specificity, but were significantly smaller and produced a lower number of offspring.These results suggest that innate host-acceptance behavior is likely to reduce parasitism on some nontarget Pentatomoidea which T. japonicus will encounter in the field. Future efforts should be made to examine the ability of the wasp to reproduce long term on nontarget species when H. halys eggs are limited.

Thousand cankers disease (TCD) is a pest complex formed by the association of the walnut twig beetle (WTB), Pityophthorus juglandis Blackman (Coleoptera: Curculionidae: Scolytinae), with the fungal pathogen Geosmithia morbida Kolařík, Freeland, Utley and Tisserat (Ascomycota: Hypocreales: Bionectriaceae). Current monitoring and detection efforts for WTB rely on a pheromone lure that is effective over a limited distance while plant- and fungal-derived volatiles that may facilitate host location remain poorly understood. In this study, we test the hypothesis that adult beetles are attracted to volatiles of black walnut, Juglans nigra L. (Juglandaceae), and the pathogen, G. morbida. We measured the response of beetles to head-space volatiles collected from leaves and stems of 12 genotypes of black walnut and found genotypic variation in the attractiveness of host trees to adult WTB. Volatile profiles of the most attractive genotypes contained more α-pinene and β-pinene, and adult beetles were attracted to both of these compounds in olfactometer bioassays. In bioassays, we also demonstrated that adult WTB are attracted to volatiles of G. morbida. These findings suggest that, in addition to the aggregation pheromone, dispersing WTB potentially use host plant and fungal volatiles to locate suitable larval hosts. Finally, we conducted a field experiment to determine the extent to which ethanol, a common attractant for bark beetles, and limonene, a known bark beetle repellent, influence the behavior of adult WTB to pheromone-baited traps. Although ethanol did not increase trap capture, WTB were repelled by limonene, suggesting that this compound could be used to manipulate and manage WTB populations.

Intraspecific genetic variation in plants can contribute to the diversity and abundance of associated insects, though many questions remain about why some genotypes support more insects than others. Since plant secondary metabolites, which may be induced after insect attack, may potentially vary among genotypes, these compounds provide a possible explanation for insect abundance variation in plants with substantial genetic variation. In this study, we examined four genotypes of the old-field plant species Solidago altissima (L.; Asterales: Asteraceae) and asked if the abundance of the specialist aphid Uroleucon nigrotuberculatum (Olive; Hemiptera: Aphididae) was affected by genotype and previous foliage damage by a specialist beetle. We hypothesized that different genotypes and prior herbivory would result in different quantities of terpenes produced by S. altissima, and that terpenes would affect aphid abundance. We found evidence of foliar terpene induction in a greenhouse environment, and significant differences in terpene production among genotypes in a field setting, though prior damage had little effect on aphid abundance in the field. There were significant effects of genotypes on aphid abundance, as well as genotype effects on terpenes and foliar nutrients (leaf N and C:N). Noteworthy was a change in the allocation of particular terpenes among genotypes that related to aphid abundance. Our analyses demonstrated that phytochemicals, and especially terpenes, related to aphid abundance. This study adds to a previous finding that variation in leaf terpenes in S. altissima provides a partial explanation for variable abundance among genotypes of a specialist aphid, and suggests that differences in the allocation of compounds is important.

Harlequin bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae), is a widespread pest that feeds on a variety of brassicaceous crops and other plants.To understand olfactory cues that mediate host-finding, and their possible utility in pest management, we deployed aggregation pheromone (mixed murgantiols = 10,11-epoxy-1-bisabolen-3-ols) and/or isothiocyanate (ITC) host plant volatiles with potted host plants and nonhost soybean, in field choice bioassays. Adults of both sexes were strongly attracted (10–31×) to collard host plants baited with pheromone lures, compared with unbaited collards, as were nymphs. Collard plants baited with lures containing allyl and/or benzyl-ITC showed a 1.3× and 1.9× increase in attractiveness, respectively, neither differing by life-stage nor sex; multiple lures showed additive attraction. Nonhost soybean, baited with pheromone lure, was 4.6–7.5× more attractive to adults than unbaited collard; conversely, baited collard was 124× more attractive than unbaited soybean. The stark difference in observed effect of pheromone lure between unpoisoned plants, and those poisoned with imidacloprid, indicated that attraction was underestimated by circa-daily counts of unpoisoned plants, presumably because if not poisoned, bugs rapidly abandoned the baited nonhost soybean plant. Results indicate that harlequin bugs can be misled to encounter and feed on nonhosts by their aggregation pheromone, but additional means may be needed to retain them. Attraction to hosts is increased both by the aggregation pheromone, and at least two host plant volatiles, allyl and benzyl-ITC. These results contribute to our knowledge of host finding in harlequin bug, and to possible trapping and trap cropping schemes for pest management.

Natural mortality factors are responsible for regulating pest populations in the field. However, plant attributes such as the variety and phenological stage can influence the performance of these factors. Therefore, we investigated the performance of the natural mortality factors of Aphis gossypii (Glover; Hemiptera: Aphididae) as a function of the plant variety and phenology. To investigate the performance of these factors, we evaluated the mortality of A. gossypii caused by natural mortality factors for 2 yr in field conditions in transgenic (Bacillus thuringiensis/Roundup Ready) and non-transgenic cotton crops during vegetative, flowering, and fruiting stages. The natural mortality factors were affected similarly between the transgenic and non-transgenic plants; however, differences were observed in their performance, depending on the phenological stage of the cotton plant. Compared with other stages, predation was higher in the flowering stage, whereas the mortality caused by rainfall was higher in the vegetative stage. Coccinellid beetles were primarily responsible for the predation on A. gossypii. These findings highlight that the performance of the natural mortality factors of A. gossypii varied more as a function of the phenological stage of cotton than of the variety.

The oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), is a primary pest of stone fruits that cause significant economic damage. Larvae, which enter the host plant through shoot tips, damage shoots, and ripe fruits. Native to Asia, this pest now occurs in many fruit-growing countries, including the United States and Canada. Though the pest was previously reported from many states within the United States, its current distribution and the environmental variables that influence its distribution are not properly identified. The objectives of this study were to 1) identify the environmental factors associated with G. molesta current distribution, 2) predict the current distribution of G. molesta in Washington State (WA) using Maxent and Climex models, 3) identify those areas within WA best suited for establishment of pest free zones, areas of low pest prevalence, and pest free production areas, and 4) identify regions most at risk for further expansion of G. molesta populations as a function of climate change. The current models predicted a small portion of central WA is suitable to support G. molesta, which is consistent with observed distributions. However, climate change models predict that more areas will become suitable for the pest. These results indicate that action should be taken to monitor and reduce current populations of G. molesta to stem its potential expansion into the major commercial tree fruit production areas in the state.

Western cherry fruit fly, Rhagoletis indifferens (Curran; Diptera:Tephritidae), occurs in unmanaged cherries (Prunus spp.) across dry climates in Washington State and other regions in western United States and Canada. To help explain the fly's distribution in arid climates, we determined the effects of adding water to bare and grass-covered soils on pupal survival rates and adult emergence patterns of R. indifferens in central Washington. Water was added (‘irrigated’) or not to bare soil and grass-covered soil in cylinders pressed into the ground. Larvae were added to cylinders and pupal survival and adult fly emergence determined over three seasons. Irrigating bare soil had no effect on pupal survival or adult emergence, but in grass-covered soil, irrigation increased pupal survival (15.2–17.0% vs 6.7–9.5%) and adult emergence (2 of 3 yr, 12.8 and 24.1 vs 1.1 and 11.6%; no difference in 1 yr). Pupal survival was greater in bare (24.5–47.7%) than grass-covered soil (6.7–17.0%). Moisture was higher in irrigated than unirrigated treatments but within irrigated treatments, moisture in bare versus grass-covered soil did not differ. In both irrigated and unirrigated treatments, humidity in soil 5 cm below the surface where many pupae reside was >60%, including during summers. Results suggest R. indifferens pupae tolerate unirrigated soils during summer because soil moisture and high humidity there can prevent desiccation, contributing to the fly's wide distribution and abundance in dry climates, and that dry, grass-covered soils or mulch barriers in mid- and late-summer could reduce fly survival under some conditions.

Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), a common zoophytophagus bug, is a biological control agent for several groups of noxious agricultural pests, including whiteflies, aphids, and leafminers. To improve mass-rearing of this species and to optimize its application in integrated pest management, nymphal survival and developmental times of this predator were examined at seven constant temperatures ranging from 14 through 34°C. Eggs developed to adulthood at all temperatures tested. Egg-adult developmental time decreased sharply with increasing temperature, except at 34°C (17.21 d), for which developmental time was significantly longer than that obtained at 31°C (15.59 d). The lowest (11.36%) and highest (28.26%) percentage of mortality was found at 28 and 14°C, respectively. To describe the development rate of immature stages of N. tenuis as a function of temperature, two linear and 26 nonlinear models were fitted. The lower temperature threshold (T₀) and thermal constant (K) of total immature stages were estimated by the ordinary (10.94°C and 318.37 DD) and Ikemoto (10.28°C and 339.57 DD) linear models. Based on the Akaike information criterion (AIC), Lactin-1, Analytis-1/Allahyari and Janisch/Kontodimas were the best models to describe the temperature-dependent development rate of egg, nymph and whole immature stages of the predator, respectively. Our findings provide information on N. tenuis biology that will improve application of this predator as a biological control agent.

We examined the effects of humidity on the metabolic rates and respiratory patterns of Gromphadorhina portentosa (Schaum) (Blattodea: Blaberidae) to determine whether insects transition from continuous, cyclical, and discontinuous (DGC) respiration in response to water conservation. Eight male G. portentosa were placed under five different humidity treatments (0, 23, 40, 60, 80% RH). Using flow through respirometry we: (i) determined the effect of humidity on metabolic rate; (ii) observed if changes in metabolic rate were correlated with changes in closed/flutter (CF) or the open (O) phase of DGC; and (iii) determined whether increased spiracular closure was correlated with an increase in water retention. Although G. portentosa had similar rates of CO₂ release when placed under 0, 40, 60, and 80% RH, cockroaches placed at 23% RH had a significantly higher metabolic rate. There was no effect of humidity on the duration of the CF phase of the DGC. However, the O phase of DGC was significantly longer when G. portentosa was placed at humidity levels above 23% RH. Interestingly, we saw that the average rate of mass lost to the environment did not change when cockroaches were placed at humidity levels ranging from 0 to 80% RH.This suggests that modulation of the spiracles allows G. portentosa to regulate the amount of water lost to the environment.

Many studies have been conducted to investigate synergism among insecticidal proteins; however, a consensus on minimal data requirements and interpretation is lacking. While some have concluded that all additive predictive-type models should be abandoned, we advocate that additivity models can remain useful as assessment tools and that an appropriately designed interaction study will never systematically underestimate the existence of synergism, irrespective of which additivity model (or none at all) may be used. To generate the most meaningful synergy assessment datasets in support of safety assessments, we highlight two beneficial steps to follow: (i) select a testing model which is the most consistent with current knowledge regarding the action of the insecticidal proteins and (ii) avoid using bioassay methods which may result in excess response heterogeneity. We also outline other experimental design elements to consider, which may be crucial for conducting future studies of this type. A contrast of underlying testing assumptions associated with the additivity models is provided, along with a comprehensive review of interaction data for Cry1, Cry2, Cry3, Cry9, and Vip3A insecticidal proteins. Our review captures four recurrent findings: i) experiments reporting synergistic interactions are a minority, ii) the degree of synergism reported is low in magnitude, iii) reported interactions are sometimes equivocal/inconclusive due to unconfirmed model assumptions or other bioassay challenges, and iv) due to biological response variation many of the reported interactions may be artefactual. A brief overview of the positioning of interaction testing data in safety assessments of GM food crops is also provided.