Efficacy and residual toxicity of chitosan for Rhagoletis pomonella (Diptera: Tephritidae).

Chitosan is a naturally derived polymer that has significant potential for use as a bioinsecticide. Despite this, there is a lack of research as to the efficacy of chitosan for many insect pest species. The apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), is one such pest for which chitosan toxicity has not been explored. In this study, the toxicity of chitosan for R. pomonella adults was tested via no-choice feeding assays. An aging trial was further used to test the mortality of flies provided dried chitosan-sucrose treatments (CST), which were aged for 0 or 3 days in greenhouse conditions. This study found that the CST is toxic for R. pomonella adults when ingested, leading to a significant increase in the rate of mortality compared to control groups. The use of dried chitosan, however, did not change the mortality of flies, suggesting this will not be an effective delivery mechanism. Effective biopesticide delivery systems have not been defined for chitosan use outside of a laboratory, indicating the need for further research testing delivery mechanisms. It is suggested that an effective method of delivery can be as a food-based bait in attract-and-kill traps, as chitosan must be ingested to kill flies. Forming a viscous solution, chitosan may be best suited to these lure systems.

Effects of nonnutritive sugar inclusion in laboratory diets and attracticidal spheres on survivorship and mobility of 2 Dipteran species, Rhagoletis pomonella (Diptera: Tephritidae) and Drosophila suzukii (Diptera: Drosophilidae).

Native apple maggot fly, Rhagoletis pomonella, and invasive spotted-wing drosophila, Drosophila suzukii, are key pests of apple and small fruit, respectively, in the United States. Both species are typically managed with standard insecticide applications. However, interest in alternative strategies that result in insecticide reductions has led to evaluations of nonnutritive sugars as toxicants for Drosophila species and development of attracticidal spheres for both species. Here, we evaluated the survivorship of R. pomonella and D. suzukii when provided with standard diets that substituted saccharin, sucralose, aspartame, erythritol, dextrose, or mannitol for the sucrose component and compared them with standard diets and water-only controls for up to 15 days. Presence of erythritol and mannitol significantly decreased survivorship of R. pomonella and erythritol significantly decreased the survivorship of D. suzukii. However, mobility trials following a 2 h exposure to aqueous solutions of each sugar treatment resulted in no strong impact on either species. Survivorship after 30 min exposure to erythritol or mannitol alone, or in combination with varying concentrations of sucrose (serving as a phagostimulant) at 30 min and 24 h were evaluated for both species. Only D. suzukii survivorship was affected with decreased survivorship on erythritol:sucrose solutions of 20:0% and 15:5% for 24 h. Based on all results, erythritol appeared most promising, and was integrated into attracticidal spheres as a toxicant but even at the highest concentration, survivorship remained unaffected for either species, thus making this nonnutritive sugar impractical and ineffective as a toxicant substitute in attracticidal spheres.

Voltage-gated sodium channel gene mutation and P450 gene expression are associated with the resistance of Aphis spiraecola Patch (Hemiptera: Aphididae) to lambda-cyhalothrin.

Aphis spiraecola Patch is one of the most economically important tree fruit pests worldwide. The pyrethroid insecticide lambda-cyhalothrin is commonly used to control A. spiraecola. In this 2-year study, we quantified the resistance level of A. spiraecola to lambda-cyhalothrin in different regions of the Shaanxi province, China. The results showed that A. spiraecola had reached extremely high resistance levels with a 174-fold resistance ratio (RR) found in the Xunyi region. In addition, we compared the enzymatic activity and expression level of P450 genes among eight A. spiraecola populations. The P450 activity of A. spiraecola was significantly increased in five regions (Xunyi, Liquan, Fengxiang, Luochuan, and Xinping) compared to susceptible strain (SS). The expression levels of CYP6CY7, CYP6CY14, CYP6CY22, P4504C1-like, P4506a13, CYP4CZ1, CYP380C47, and CYP4CJ2 genes were significantly increased under lambda-cyhalothrin treatment and in the resistant field populations. A L1014F mutation in the sodium channel gene was found and the mutation rate was positively correlated with the LC50 of lambda-cyhalothrin. In conclusion, the levels of lambda-cyhalothrin resistance of A. spiraecola field populations were associated with P450s and L1014F mutations. Our combined findings provide evidence on the resistance mechanism of A. spiraecola to lambda-cyhalothrin and give a theoretical basis for rational and effective control of this pest species.

Male and Female Tortricid Moth Response to Non-Pheromonal Semiochemicals.

In eastern North America, apple orchards are often attacked by several species of tortricid moths (Lepidoptera), including Cydia pomonella, Grapholita molesta, Argyrotaenia velutinana, and Pandemis limitata. Sex pheromones are routinely used to monitor male moth populations. Adding plant volatiles to monitoring traps could increase the capture of moths of both sexes and improve the effectiveness of mating disruption systems. This study sought to quantify the attraction of adults of four tortricid moth species to five olfactory treatments, namely (1) Pherocon® CM L2-P, (2) Pherocon Megalure CM 4K Dual® (=Megalure), (3) Megalure + benzaldehyde, (4) TRE 2266 (linalool oxide + (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT)), and (5) TRE 2267 (linalool oxide + DMNT + benzaldehyde), in non-mating disrupted commercial apple orchards in Massachusetts. The commercial lure Megalure was attractive to both sexes of G. molesta and C. pomonella. The addition of benzaldehyde to TRE 2266 or to Megalure significantly increased the capture of male G. molesta during the mid and late season of 2021. Only when benzaldehyde was added to TRE 2266 did the latter lure attract P. limitata in 2020 and 2021. The greatest number of tortricid moths (all four species combined) was captured by TRE 2267. This finding highlights the opportunity to enhance the attractiveness of a commercial lure through the addition of benzaldehyde, an aromatic compound, to Megalure. The potential of these additional volatiles to detect moths in a mating-disrupted orchard and/or remove female moths as a component of a management system is discussed.

Methyl salicylate improves the effectiveness of the odor-baited trap tree approach for adult plum curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), monitoring and attract-and-kill.

In commercial apple orchards, the odor-baited trap tree approach involving the synergistic lure composed of benzaldehyde (BEN) and the PC aggregation pheromone grandisoic acid (GA) serves as an effective monitoring tool as well as an attract-and-kill strategy for plum curculio (PC), Conotrachelus nenuphar Herbst. (Coleoptera: Curculionidae), management. However, the relatively high cost of the lure and the degradation of commercial BEN lures by UV light and heat discourage its adoption by growers. Over a 3-yr period, we compared the attractiveness of methyl salicylate (MeSA), either alone or in combination with GA, to plum curculio (PC) with that of the standard combination of BEN + GA. Our main goal was to identify a potential replacement for BEN. Treatment performance was quantified using 2 approaches: (i) unbaited black pyramid traps (2020, 2021) to capture PC adults and (ii) PC oviposition injury (2021, 2022) on apple fruitlets of trap trees and of neighboring trees to assess potential spillover effects. Traps baited with MeSA captured significantly more PCs than unbaited traps. Trap trees baited with a single MeSA lure and 1 GA dispenser attracted a similar number of PCs as trap trees baited with the standard lure composed of 4 BEN lures and 1 GA dispenser based on PC injury. Trap trees baited with MeSA + GA received significantly more PC fruit injury than neighboring trees suggesting no or limited spill-over effects. Our collective findings suggest that MeSA is a replacement for BEN thereby cutting costs of lures by ca. 50% while maintaining trap tree effectiveness.

Combined application of entomopathogenic nematodes and fungi against fruit flies, Bactrocera zonata and B. dorsalis (Diptera: Tephritidae): laboratory cups to field study.

BACKGROUND: The peach fruit fly, Bactrocera zonata, and the Oriental fruit fly, B. dorsalis (Diptera: Tephritidae), are economically important fruit fly species in various regions of the world. We evaluated the effects of separate and combined applications of the entomopathogenic fungi (EPF) Beauveria bassiana (WG-18) and Metarhizium anisopliae (WG-02), and the entomopathogenic nematodes (EPNs) Heterorhabditis bacteriophora (VS strain) and Steinernema carpocapsae (ALL strain) against larvae, pupae and pharate adults, of B. zonata and B. dorsalis under laboratory, glasshouse and field cage conditions. RESULTS: Combined applications of EPF and EPNs produced greater mortality than individual treatments under all conditions. Against both species, the combination of B. bassiana and H. bacteriophora consistently exerted strong effects that were similar to the combined application of B. bassiana and S. carpocapsae whereas M. anisopliae applied with S. carpocapsae was least effective in all combinations. In a laboratory bioassay, synergistic interactions were detected between B. bassiana and H. bacteriophora applied against larvae and pharate adults of both fly species, between B. bassiana and S. carpocapsae against larvae of both species and pharate adults of B. zonata, and between M. anisopliae and H. bacteriophora against B. zonata larvae. Other combined treatments resulted in additive effects, especially against fly pupae. In a potted soil bioassay, there were only additive interactions in all combinations against different stages of both flies. The 3rd instar of both flies was more susceptible than pharate adult and pupal stages. Additive interactions between EPNs and EPF were detected in the glasshouse against 3rd instars and pupae, and under field conditions against 3rd instars of both fly species. CONCLUSION: These results indicate how particular combinations of entomopathogenic fungi and nematodes could be deployed in integrated pest management of tephritid fruit flies in orchard agro-ecosystems. © 2022 Society of Chemical Industry.

Effects of diluted Concord grape juice laced with sodium chloride and selected boron-containing compounds on attraction, consumption, crop muscle contractions, and mortality of adult Drosophila suzukii Matsumura (Diptera: Drosophilidae).

BACKGROUND: In recent years, there has been interest in low-cost, reduced-risk materials that could be used for attract-and-kill of the invasive pest, spotted-wing Drosophila, Drosophila suzukii. This pest causes heavy economic damage to soft-skinned fruits in many countries. In this study, we evaluated physiological and behavioral effects of adding either borax, boric acid, or sodium chloride to diluted Concord grape juice (DGJ), a material that is attractive to adult D. suzukii. RESULTS: Results showed that the addition of borax, sodium chloride and boric acid did not significantly affect the response of adult D. suzukii, relative to DGJ alone. Increases in concentrations (to 5% and 10%) of borax, sodium chloride and boric acid were correlated with decreased ingestion of materials. Mortality of males and females was almost 100% with lower concentrations (1% and 5%) of borax and boric acid within 72 h. The higher concentrations of sodium chloride (5% and 10%) resulted in 100% mortality of both sexes within 72 h. There was no significant effect of chemicals on the number of crop contractions of flies when fed for 4 h. CONCLUSIONS: This study suggests that some substances such as boric acid and borax may act as toxicants without influencing the behavioral response of D. suzukii. © 2021 Society of Chemical Industry.

Sublethal Effects of Abamectin on the Development, Reproduction, Detoxification Enzyme Activity, and Related Gene Expression of the Oriental Fruit Moth (Lepidoptera: Tortricidae).

Grapholita molesta is one of the most important fruit pests worldwide. Abamectin is a biological pesticide frequently used to control fruit borers like G. molesta in part owing to its translaminar properties. In this study, we characterized the toxicity of abamectin to G. molesta larvae using the diet incorporation method. The sublethal effects of abamectin on the development, reproduction, detoxification enzyme activity, and related gene expression of G. molesta were assessed. The results showed that the LC20 and LC50 values of the insecticide against G. molesta 72 h post-treatment were 1.17 mg L-1 and 5.85 mg L-1, whereas the LC20 and LC50 values 96 h post-treatment were 0.34 mg L-1 and 3.63 mg L-1. When compared to the control, sublethal concentrations of abamectin 1) significantly increased the mortality of the larvae, prepupae, and pupae of G. molesta, 2) prolonged the duration of 3rd to 5th instar larva, prepupal and pupal periods, 3) shortened the longevity of adults, and 4) reduced female fecundity. The enzymatic activity of glutathione S-transferase (GST) varied significantly after exposure to sublethal concentrations of abamectin, but the cytochrome P450 monooxygenases and carboxylesterase activity were not significantly affected. Thirteen of the 25 GST genes were significantly upregulated under different sublethal concentrations of abamectin. The combined findings increase our understanding of the effects of abamectin on G. molesta and the potential role of GSTs in the metabolic interactions of abamectin in this pest, and have applications for more rational and effective use of abamectin to control G. molesta.

Evaluation of Locally Isolated Entomopathogenic Fungi against Multiple Life Stages of Bactrocera zonata and Bactrocera dorsalis (Diptera: Tephritidae): Laboratory and Field Study.

Fruit flies including Bactrocera zonata and B. dorsalis (Diptera: Tephritidae) are considered major pests of orchard systems in Pakistan. This study evaluated the laboratory virulence, sub-lethal effects, horizontal transmission, greenhouse, and field-cage efficacy of locally isolated entomopathogenic fungi (EPF) against B. zonata and B. dorsalis. In virulence assays against third instars and adults, all 21 EPF isolates (Beauveria bassiana and Metarhizium anisopliae) tested were pathogenic and caused varying levels of mortality to the fruit flies. Based on the initial screening, four isolates (B. bassiana WG-21 and WG-18 and M. anisopliae WG-07 and WG-02) were selected for further study. The isolate WG-18 was the most virulent against larvae and adults of B. zonata and B. dorsalis followed by WG-21, WG-02, and WG-07. In both species, adults were more susceptible than larvae to all isolates, and pupae were the least susceptible. Isolates WG-18 and WG-21 strongly decreased female fecundity and fertility, the highest adult and larval mortality, and longest developmental time of larvae and pupae. Fungal conidia were disseminated passively from infected to healthy adults and induced significant mortality, particularly from infected males to non-infected females. In greenhouse and field-cage experiments, WG-18 and WG-21 were the most effective isolates in reducing adult emergence when applied to larvae and pupae of both fruit fly species. Our results indicate that B. bassiana isolates WG-18 and WG-21 were the most virulent against multiple life stages of B. zonata and B. dorsalis, and also exerted the strongest sub-lethal effects.

Effects of chitosan and erythritol on labellar taste neuron activity, proboscis extension reflex, daily food intake, and mortality of male and female spotted-winged drosophila, Drosophila suzukii.

In recent years, there has been interest in reduced-risk materials with insecticidal properties for the invasive pest spotted-wing drosophila, Drosophila suzukii. Here, we compared the peripheral sensitivity (via the tip-recording technique, used to monitor the neural activity of gustatory receptor neurons [GRNs]) and palatability (via the Proboscis Extension Reflex [PER]) of chitosan, a polysaccharide derived from chitin, with that of erythritol, a sugar alcohol, to male and female D. suzukii. Because in some insect species it has previously been shown that chitosan has some insecticidal properties, then treatment effects on mortality rates of male and female D. suzukii were quantified. Physiological recordings from the l-type labellar sensilla showed that erythritol evoked responses from one GRN, while chitosan elicited spiked activity from a second one. The first PER bioassay revealed that the level of response to erythritol increased significantly for males and females as the concentrations increased, and the effect of fly sex was non-significant. The second PER bioassay compared the male and female response to chitosan and erythritol each at 0.125, 0.25, 0.5, 1, and 2% concentrations. The overall female PER to erythritol was significantly greater than that exhibited by males, and no differences were noted between sexes when chitosan was evaluated. These results indicate that chitosan alone can elicit PER responses in adult D. suzukii. In the third experiment, chitosan was toxic to D. suzukii. When combined with sucrose (2%), chitosan elicited high levels (80-100%) of mortality of adult D. suzukii within 3 days, particularly in males. The presence of erythritol did not seem to increase the toxic effect of chitosan.

Olfactory Cues From Host- and Non-host Plant Odor Influence the Behavioral Responses of Adult Drosophila suzukii (Diptera: Drosophilidae) to Visual Cues.

While trapping methods for Drosophila suzukii Matsumura (Diptera: Drosophilidae) have typically relied on fermentation volatiles alone or in association with a visual stimulus, the relative contribution of visual and olfactory stimuli to the food- and host-seeking behavior of D. suzukii is poorly understood. This study quantified the type of response exhibited by male and female D. suzukii to color and the effects that volatiles (fermentation, fresh fruit, and leaf) exert on the outcome. Seven-, four- and two-choice assays were used to quantify interactions between visual and olfactory cues. When no volatiles were present in a seven-choice assay, D. suzukii preferred red, black, and green pigments. Black and red were preferred when yeast odors were present, and black alone was the most attractive color when blueberry odor was present. A strawberry leaf terpenoid, ß-cyclocitral, seemed to have overridden the flies' response to color. In four-choice assays, blueberry odor was more likely to interact synergistically with color than yeast or ß-cyclocitral. This study demonstrates that D. suzukii modulates the response to multimodal sensory modalities (vision and olfaction) depending, to some extent, on the type of olfactory stimuli. Our findings also provide insight into the relative importance of vision as a function of odor quality in this invasive species.

Contrasting Behavioral and Electrophysiological Responses of Eucryptorrhynchus scrobiculatus and E. brandti (Coleoptera: Curculionidae) to Volatiles Emitted from the Tree of Heaven, Ailanthus altissima.

Eucryptorrhynchus scrobiculatus and E. brandti (Coleoptera: Curculionidae) are host-specific pests of Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae), causing extensive damage to the host. There are no effective attractants available for pest management. The main aim of this study was to explore the role of host plant-derived volatiles in the behavioral response of both weevil species. In a field experiment, both weevil species showed positive response to phloem, and there was no preference for phloem associated with healthy or injured trees. Significantly more E. brandti adults responded to the olfactory treatments compared to E. scrobiculatus. In a large-arena experiment, both males and females of E. scrobiculatus significantly preferred phloem from the tree trunk while adults of E. brandti responded in significantly greater numbers to tree limbs than to any other parts of host. Females and males of E. scrobiculatus responded positively to all parts of host tested in the Y-tube bioassay, while E. brandti adults were only attracted by the phloem from healthy and injured trees. There were dissimilar electroantennographic responses to compounds such as 1-hexanol and (1S)-(-)-ß-pinene between the two weevil species. This study represents the first report documenting behavioral and electrophysiological responses of E. scrobiculatus and E. brandti to volatiles from various parts of A. altissima and findings may aid efforts to develop attractants.

Virulence of Entomopathogenic Fungi to Rhagoletis pomonella (Diptera: Tephritidae) and Interactions With Entomopathogenic Nematodes.

The objectives of this study were to quantify the virulence of four entomopathogenic fungal species to pupae of Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) and to determine the potential to combine entomopathogenic fungi (EPFs) and entomopathogenic nematodes (EPNs) for biological control of this pest. The four species of EPFs included Beauveria bassiana (strain GHA), Metarhizium brunneum (strain F52), Isaria javanica (wf GA17), and Isaria fumosorosea (Apopka 97 strain). In laboratory assays, all fungi reduced adult emergence but there were no differences between fungal species. Isaria javanica and M. brunneum were examined further in a EPFs and EPNs bioassay that also included the EPNs Steinernema carpocapsae (ALL strain) and S. riobrave (355 strain). All nematodes and fungi were applied either alone or in combination (fungus + nematode). There were no differences between species within the same entomopathogen group (fungi and nematodes). However, the treatment with S. riobrave resulted in lower R. pomonella emergence than either fungal species. The combination of S. riobrave and I. javanica resulted in the lowest R. pomonella emergence (3%) at fourth-week interval, which was significantly lower than any of the single-agent applications, yet virulence of the other three combination treatments was not different from their respective nematode treatments applied alone. Additive interactions were detected for all fungus-nematode combinations. This study suggests that application of entomopathogenic nematodes and fungi could be an effective option to suppress R. pomonella populations.

The Mayan Tropical Rainforest: An Uncharted Reservoir of Tritrophic Host-Fruit Fly-Parasitoid Interactions.

Over a two-year period, we surveyed natural areas of the Mayan rainforest in Quintana Roo, Mexico. We found 11 species of Anastrepha Schiner (Diptera: Tephritidae) infesting 25 species of fruits belonging to ten plant families. We report the first records of 10 host plant species of the genus Anastrepha, which include the first report of a plant family (Putranjivaceae) serving as host of Anastrepha fraterculus (Wiedemann) infesting Drypetes lateriflora (Sw.) Krug and Urb. (Putranjivaceae). Pouteria reticulata (Engl.) Eyma (Sapotaceae) was found, for the first time, to be infested by Anastrepha serpentina (Wiedemann) and by a new undescribed species of Anastrepha. We also report Casimiroa microcarpa Lundell (Rutaceae) as a possible ancestral host for the Mexican fruit fly, Anastrepha ludens (Loew), in Central America. The family Sapotaceae was the best-represented host group with three fruit fly species recovered: A. serpentina, an economically-important species, found in eight host plants, and A. hamata and A. sp. (new species). We recorded six species of koinobiont parasitoids: Doryctobracon areolatus Szepligeti, Utetes (Bracanastrepha) anastrephae Viereck, Opius hirtus Fisher, and Doryctobracon zeteki Musebeck, (all Braconidae), and Aganaspis pelleranoi (Brethés) and Odontosema anastrephae Borgmeier, (both Figitidae). All these parasitoid species represent at least a new report for their host plants. Of the whole parasitoid community, D. areolatus was the most important parasitoid species with 52.7% of presence in 12 host plant species, parasitizing six fruit fly species. The interaction between fruit flies and their parasitoids with host plants depends on fruit availability, which is crucial for the survival of each of these species. Conserving the landscape of the Mayan rainforest is important not only for species conservation, but also for the maintenance of fruit fly host plants in orchard agroecosystems in southeastern Mexico.

Potential of entomopathogenic nematodes against the pupal stage of the apple maggot Rhagoletis pomonella (Walsh) (Diptera: Tephritidae).

The apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), is considered a key pest of apples and is native to the eastern United States. The virulence of seven different species of entomopathogenic nematodes (EPN) was assessed against pupae of R. pomonella under laboratory conditions. Nematode species and strains included Steinernema carpocapsae (ALL strain), Steinernema feltiae (SN strain), Steinernema riobrave (355 strain), Steinernema glaseri (VS strain), Heterorhabditis bacteriophora (VS strain), Heterorhabditis indica (HOM1 strain), and Heterorhabditis megidis (UK211 strain). We conducted three bioassays: (i) short-term exposure cup bioassay (7 d), (ii) long-term cup bioassay (30 d), and (iii) pot bioassay (30 d). In the short-term exposure bioassay, all nematode strains (applied at 54 infective juvenile nematodes (IJs) cm-2) significantly reduced (range: 42.9-73.8%) insect survival relative to the control, but no differences were observed among the treatments. For the long-term exposure bioassay, using the same EPN application rate as the short exposure assay, all treatments reduced adult R. pomonella emergence compared with the control. Steinernema riobrave was the most virulent (28.3% survival), and S. glaseri and H. megidis were the least virulent (53.3% survival). In the pot experiment, S. riobrave and S. carpocapsae (applied at 27 IJs cm-2) had the highest virulence (23.3 and 31.7% survival of R. pomonella, respectively), while H. bacteriophora was the least effective (68.33% survival). Our results indicate that S. riobrave, S. carpocapsae, and S. feltiae have substantial potential to attack R. pomonella pupae, and their field application under the tree canopy (prior to adult emergence) in the spring when temperatures are conducive might be a good option for successful IPM of apple maggot fly.The apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), is considered a key pest of apples and is native to the eastern United States. The virulence of seven different species of entomopathogenic nematodes (EPN) was assessed against pupae of R. pomonella under laboratory conditions. Nematode species and strains included Steinernema carpocapsae (ALL strain), Steinernema feltiae (SN strain), Steinernema riobrave (355 strain), Steinernema glaseri (VS strain), Heterorhabditis bacteriophora (VS strain), Heterorhabditis indica (HOM1 strain), and Heterorhabditis megidis (UK211 strain). We conducted three bioassays: (i) short-term exposure cup bioassay (7 d), (ii) long-term cup bioassay (30 d), and (iii) pot bioassay (30 d). In the short-term exposure bioassay, all nematode strains (applied at 54 infective juvenile nematodes (IJs) cm−2) significantly reduced (range: 42.9-73.8%) insect survival relative to the control, but no differences were observed among the treatments. For the long-term exposure bioassay, using the same EPN application rate as the short exposure assay, all treatments reduced adult R. pomonella emergence compared with the control. Steinernema riobrave was the most virulent (28.3% survival), and S. glaseri and H. megidis were the least virulent (53.3% survival). In the pot experiment, S. riobrave and S. carpocapsae (applied at 27 IJs cm−2) had the highest virulence (23.3 and 31.7% survival of R. pomonella, respectively), while H. bacteriophora was the least effective (68.33% survival). Our results indicate that S. riobrave, S. carpocapsae, and S. feltiae have substantial potential to attack R. pomonella pupae, and their field application under the tree canopy (prior to adult emergence) in the spring when temperatures are conducive might be a good option for successful IPM of apple maggot fly.

Toward the Integration of an Attract-and-Kill Approach with Entomopathogenic Nematodes to Control Multiple Life Stages of Plum Curculio (Coleoptera: Curculionidae).

Efforts to reduce insecticide inputs against plum curculio, Conotrachelus nenuphar, a key pest of apples in eastern North America, include perimeter-row insecticide sprays applied after the whole-orchard petal fall spray to manage dispersing adults and, more recently, insecticide sprays confined to odor-baited trap trees. Entomopathogenic nematodes (EPNs) are virulent to ground-dwelling stages of C. nenuphar, and may be applied to the ground underneath trap-tree canopies. Here, we (1) compared the efficacy of the odor-baited trap tree approach with grower-prescribed (=grower standard) sprays to manage C. nenuphar populations over a six-year period in seven commercial apple orchards in New England; and (2) assessed the performance of the EPN Steinernema riobrave at suppressing ground-dwelling stages of C. nenuphar. In addition, the performance of S. riobrave was compared against that of S. carpocapsae and S. feltiae in one year. Across the six years, percent fruit injury on trap tree plots averaged 11.3% on odor-baited trap trees and 1.4% on unbaited trees in grower standard plots, highlighting the ability of trap trees to aggregate C. nenuphar activity and subsequent injury. Mean percentage injury on fruit sampled from interior trees, the strongest measure of treatment performance, in trap tree plots did not differ significantly from that recorded on interior trees in grower standard spray plots (0.95 vs. 0.68%, respectively). Steinernema riobrave consistently reduced C. nenuphar populations as indicated by the significantly lower number of adult C. nenuphar that emerged from the soil, when compared to water control. Steinernema carpocapsae and S. riobrave performed similarly well, and both EPN species outperformed S. feltiae. Our combined findings indicate that an IPM approach that targets multiple life stages of C. nenuphar has the potential to manage this pest more sustainably in a reduced-spray environment.

Electrophysiological and Behavioral Responses of Drosophila suzukii (Diptera: Drosophilidae) Towards the Leaf Volatile ß-cyclocitral and Selected Fruit-Ripening Volatiles.

The spotted-wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is attracted to numerous volatile organic compounds (VOCs) emitted from several ripening, small fruit crops. However, the strawberry leaf terpenoid, ß-cyclocitral, is reportedly very attractive to D. suzukii (but not to all Drosophila spp.). This suggests that leaf and fruit VOCs may be critical sources needed to further develop a more species-specific D. suzukii monitoring lure, or semiochemically based attract-and-kill systems. This study investigated the electrophysiological responses of male and female D. suzukii towards selected host fruit-ripening VOCs and ß-cyclocitral, along with behavioral responses toward combined fruit VOCs with ß-cyclocitral. Electroantennogram (EAG) results revealed a positive dose-response, for both sexes, as concentrations increased for all VOCs tested. For ß-cyclocitral, hexyl acetate and methyl butyrate, the mean male EAG responses were significantly greater than the female responses at lower doses. In caged behavioral bioassays, only in the ß-cyclocitral treatments were the mean number of flies captured (sexes combined) significantly greater than that captured in solvent (mineral oil) controls. Our study has demonstrated that while single fruit-based VOCs alone are not enough to cause a strong behavioral attraction by both male and female D. suzukii, the addition of ß-cyclocitral did produce a significant attraction response from both sexes. In both bioassays, males had higher responses to ß-cyclocitral than females, which suggest a greater sensitivity to this compound. Further studies are needed to ascertain the role ß-cyclocitral may play in the development of a more species-specific D. suzukii monitoring lure.

ß-cyclocitral synergizes the response of adult Drosophila suzukii (Diptera: Drosophilidae) to fruit juices and isoamyl acetate in a sex-dependent manner.

Semiochemicals play a pivotal role in the location, evaluation, and utilization of hosts by herbivorous insects. Mixtures of host plant-derived compounds are often required to elicit appropriate levels of response to olfactory stimuli. In multiple-choice bioassays, we characterized the response of adult Drosophila suzukii to foliage- and fruit-based synthetic compounds tested alone and in association with grape and tart cherry juices, and assessed whether synergistic interactions among olfactory stimuli are involved in the olfactory-driven behavior of D. suzukii. Our results established (1) significant attraction of females (but not males) to ß-cyclocitral and isoamyl acetate when tested singly, (2) the presence of a synergistic interaction between ß-cyclocitral and cherry juice only for females, and (3) the presence of a synergistic interaction between ß-cyclocitral and isoamyl acetate but only in the case of males. Our findings increase our understanding of male and female D. suzukii olfactory responses to synthetic compounds and fruit juices as sources of attractants. Combinations of foliage- and fruit-based compounds may be needed to increase SWD attraction.

The 'Botanical Triad': The Presence of Insectary Plants Enhances Natural Enemy Abundance on Trap Crop Plants in an Organic Cabbage Agro-Ecosystem.

Habitat manipulation through the incorporation of non-crop plants such as trap crops (to lure pests away from the cash crop) and insectary plants (to provide resources for natural enemies) into agro-ecosystems is an ecological approach to pest management. In a field-scale study, we quantified the effects of integrating the use of trap crops with insectary plants as a novel method to control pest herbivores in an organic cabbage agro-ecosystem. We hypothesized that pests would be concentrated in the trap crop habitat and suppressed by insectary-subsidized natural enemies in situ. We documented arthropod abundance (both adults and immature stages) associated with (1) two insectary plant species (sweet alyssum, Lobularia maritima, and buckwheat, Fagopyrum esculentum) either alone or in combination; (2) a trap crop mixture of mighty mustard (Brassica juncea), red Russian kale (Brassica oleracea var. acephala), and glossy collards (Brassica oleracea var. italica), and (3) cabbage cash crop (Brassica oleracea var. capitata). Trap crops were more attractive to pests than the cash crop. On a per-plant basis, densities of the herbivores Evergestis rimosalis, Trichoplusia ni, and Plutella xylostella were 154, 37, and 161× greater on the kale trap crop than on the cabbage cash crop, and 54, 18, and 89× greater on the collards trap crop than on the cash crop. Insectary plants contributed to the consumption of pests that aggregated on the trap crop. Parasitism of E. rimosalis by the braconid wasp Cotesia orobenae was significantly increased, and the abundance of eggs and larvae of the predatory coccinellid beetle Coleomegilla maculata was greater on the trap crop in the presence of insectary plants compared to trap crops that lacked insectary plants. The 'Botanical Triad' of cash crop, trap crop, and insectary plants represents a new type of agro-ecosystem manipulation that integrates ecosystem service providers (e.g., predators and parasitoids) within the cropping system.

Effect of Physiological State on Female Melon Fly (Diptera: Tephritidae) Attraction to Host and Food Odor in the Field.

Foraging behavior of wild female melon fly, Bactrocera (Zeugodacus) cucurbitae Coquillett, a worldwide pest of economically important cucurbit crops, was examined through mark and recapture studies in both wild (Kona: dominated by the invasive weed ivy gourd, Coccinea grandis [L.] Voigt [Cucurbitaceae]), and cultivated (Kapoho: dominated by papaya, Carica papaya L. [Caricaceae] orchards) habitats on Hawaii Island. In particular, the extent to which wild melon flies and color-marked F2 females responded to cucumber odor and Solulys yeast hydrolysate laced with ammonium acetate (1%, wt/vol) according to sexual maturity stage and degree of protein hunger was documented. Kona results indicated that more wild and color-marked F2 females responded to cucumber (Cucumis sativus L. [Cucurbitaceae]) odor than to protein odor with the exception of captured wild flies without eggs, which responded similarly to protein bait and cucumber odor. Results with captured wild females and color-marked F2 females in Kapoho suggested a significant preference for cucumber odor over protein odor regardless of whether or not they had eggs in their ovaries with the exception of protein-deprived color-marked F2 females, which responded to both odors in equal numbers. Implications of these new findings based on wild melon flies in natural habitats are discussed with respect to integrated pest management control strategies with protein bait sprays used in Hawaii. The possibility of adding cucurbit volatiles to protein-based baits is discussed.