Location: Temperate Tree Fruit and Vegetable Research
2018 Annual Report
Objectives
This research will provide basic and applied information for the development and transfer of sustainable and environmentally acceptable methods and technologies for management of insect pests of temperate tree fruit crops. The objectives are:
Objective 1: Develop new knowledge of the behavior, physiology, ecology, and biochemistry of insect pests and their natural enemies to suggest novel approaches to pest management and improve the use of existing methods, with focus on pest-host plant interactions of pear psylla and brown marmorated stink bug, pest-microbe interactions of codling moth and spotted wing drosophila, ecological and physiological criteria that limit pest distribution and abundance, and the functionality of codling moth receptors.
Subobjective 1A. Determine and characterize interactions between pear trees and pear psylla and between the brown marmorated stink bug (BMSB) and preferred host plants.
Subobjective 1B. Determine if volatiles emanating from microbial species found in the honeydew of aphids, mealybugs and psyllids are attractive to natural enemies.
Subobjective 1C. Determine factors affecting pupal mortality and adult emergence of western cherry fruit fly (WCFF) in the field.
Sub-objective 1D. Determine the upper and lower thermal limits for metabolism of different life stages of codling moth (CM), apple maggot (AM), and WCFF.
Subobjective 1E. Develop a CRISPR/Cas9 gene knock out system to determine functions of proteins key to CM reproduction and development.
Subobjective 1F: Determine undescribed cryptic species and undocumented range expansions of the community of minute pirate bugs in orchards and other habitats.
Objective 2: Develop alternatives to fumigation to meet quarantine restrictions for pest insects in exported fruits, with focus on developing codling moth detector technology and ecological niche modeling to determine limits to the establishment and spread of quarantined insect pests.
Subobjective 2A: Identify biochemical markers for apple fruit infested with CM larvae, in support of effort to develop detector technology.
Subobjective 2B: Improve ecological niche models for the potential of tree fruit pests of quarantine concerns to establish and spread in potential new export markets.
Objective 3: Develop and improve methods to reduce pesticide use and develop alternatives to pesticides, with focus on identifying and applying semiochemicals for pest management, and improved efficacy of natural enemies through application of foods and feeding attractants, and improvement of pear psylla control through induced or systemic acquired resistance in pear to psylla.
Subobjective 3A. Develop an attract-and-kill approach for management of codling moth and leafrollers.
Subobjective 3B. Improve efficacy of natural enemies through application of foods and feeding attractants.
Subobjective 3C. Determine field temperature influences on the efficacy of the insecticide spinosad and Delegate for management of WCFF.
Subobjective 3D. Improve pear psylla control through induced or systemic acquired resistance.
Subobjective 3E. Evaluate the use of microbial-based feeding attractants for management of codling moth.
Approach
1A. Plant resistance to pear psylla will be characterized using greenhouse and biochemical assays and electrical penetration graphs. Host preferences by brown marmorated stink bug will be assessed by determining patterns of host plant use in non-crop landscapes. Stink bug attraction to host odor will be tested using a laboratory olfactometer.
1B. To develop methods of recruiting natural enemies to orchards, microbes present in aphid and pear psylla honeydew will be identified, and odors emanating from honeydew-associated microbes will be tested for attractiveness to natural enemies.
1C. Western cherry fruit fly adult emergence will be compared from soils with varying moisture and cover to determine whether fruit fly infestations in orchards can emanate from trees located in unmanaged habitats with dry soil surfaces.
1D. Data from differential scanning calorimetry and laboratory assays will provide estimates of metabolic thermal limits for codling moth, apple maggot, and western cherry fruit fly to determine the liklihood for these pests to establish and spread in new geographies.
1E. A CRISPR/Cas9 gene knock out system will be used to determine the function of proteins key to codling moth reproduction and development in support of work to develop species-specific behavioral and physiological modifying analogs for use in pest management.
1F. To improve conservation biological control in orchards, undescribed cryptic species and undocumented range expansions of minute pirate bugs in orchards and other habitats will be described based on morphometric analyses and molecular genetics.
2A. In support of efforts to develop technology to detect codling moth infestations in stored fruit, biochemical markers for infested apples will be identified using GC-MS, and laboratory studies will be used to determine how long marker chemicals are emitted from infested fruit.
2B. Experiments conducted in environmental chambers will be used to determine the effects of tropical and sub-tropical climates and photoperiods on the growth and development of codling moth, western cherry fruit fly, and apple maggot. Data will be used to improve ecological niche models for tree fruit pests of quarantine concerns to estimate the risk for these pests to establish and spread in export markets.
3A. New attractant blends will be developed as an attract-and-kill or mass trapping approach for management of codling moth and leafrollers.
3B. Plant-based attractive lures and food provisioning will be tested as attract-and-retain method of improving biological control in orchards.
3C. Effects of temperature on the efficacy of the insecticides Spinosad and Delegate for management of western cherry fruit fly will be determined using laboratory assays.
3D. Greenhouse assays and field studies will be used to test whether elicitors of host plant defenses can be used for the control of pear psylla.
3E. Laboratory studies will be performed to determine whether the addition of different yeast species with cane sugar stimulate codling moth feeding and increase the efficacy of ingested microbial or chemical insecticides against codling moth.
Progress Report
This progress report covers year three of the continuing project to develop and improve sustainable and biorational management of insect pests of temperate tree fruits. Key pests of concern include codling moth, pear psylla, spotted wing drosophila, apple maggot, and western cherry fruit fly. Substantial progress was made on all three project objectives during fiscal year 2018.
Objective 1: Experiments have been initiated to identify mechanisms of plant resistance to pear psylla in several varieties or landraces of pear. Methods include fluorescence in situ hybridization and electrical penetration graphs to compare stylet-pathways and feeding behaviors on resistant and susceptible pear. Identification of resistance mechanisms will help breeders incorporate resistance traits in marketable varieties and will enable researchers to develop management programs which reduce the risk for pear psylla populations to develop virulence to plant resistance. Experiments are also underway to study the landscape-level migration patterns of pear psylla by optimizing a method for molecular gut content analysis to identify plant DNA in psylla for use under field conditions. This method is now being used to determine the dietary histories of field-collected psylla as they recolonize pear orchards in early spring. Identification of shelter plant sources of overwintered psylla that colonize pear will help growers target this bottlenecked stage of the population.
Biology of western cherry fruit fly: Western cherry fruit fly is abundant in unmanaged cherries in irrigated areas in the dry interior of the Pacific Northwest (PNW) of the U.S. Irrigation may allow pupae to survive in soil during hot summers when risk of heat stress and desiccation is greatest. The effects of three soil types either dry or moist on emergence times and survival of cherry fruit fly were tested in the field. Larvae were added to pots with different soils and moistures embedded in the ground in July and August 2017. Emergence of flies in 2018 was determined by placing a cage with a sticky yellow card above each pot. Data are currently being collected and will be completed by August.
Biology of apple maggot: Studies have been initiated to characterize the olfactory system of apple maggot and to identify and characterize target proteins that may lead to novel methods to keep commercial apples free of infestations. Odorant receptors, key proteins that mediate insect behaviors in response to apple volatiles, have been identified in transcriptomes generated from antennae of apple maggot males and females. With this knowledge, characterizations of specific odorant receptors are underway with the goal of identifying those that play key roles in apple maggot finding its host plant.
Biology of codling moth: Clustered regularly interspaced short palindromic repeats/CRISPR-associated 9 (CRISPR/Cas9) genome editing has been developed and successfully used to inactivate codling moth genes. This technique enables the rapid identification of novel protein targets that may be useful for codling moth control. Genes encoding odorant receptors, proteins that regulate female codling moth behaviors used to locate host plants and identify egg-laying sites, are potentially valuable targets for insect control in the orchard. In transcriptomes generated and analyzed in the past year, 15 odorant receptors that potentially respond to apple volatile compounds have been identified in both antennae (used to locate host plants) and abdomen tips (used to identify egg-laying sites). Using the transcriptome information, genes that encode the 15 odorant receptors have been identified and transcripts for 12 of these receptors have been characterized. From these characterizations, the components for CRISPR/Cas9 genome editing system have been generated. In the upcoming year, experiments will be performed to determine which odorant receptor targets have the greatest potential for use to control codling moth in the orchard.
Biology of minute pirate bugs: Understanding the role of natural enemies in orchards is made more complex with our realization that the natural enemy community in orchards and neighboring habitats includes species not previously known to occur in the PNW. One important group of predators includes the minute pirate bugs, which are generalist predators of mites, psyllids, aphids, eggs and small larvae of caterpillars, and other soft-bodied arthropods. Ongoing collecting of minute pirate bugs from the western U.S. and Canada, combined with examination of specimens obtained through loans from university museums, has led to the discovery of several unnamed species. Identifying these cryptic species was found to require a combination of behavioral assays (mating trials), plant records, morphological and anatomical examination, and analysis of DNA-sequences. At least 2 of these unnamed species appear to be substantially limited in the number of plant species with which they associate, which is behavior quite different from that of our more common and named species. Collecting efforts in the western U.S. are continuing. A key to species of North America is being developed that relies on external traits of specimens, host plant records, and structure of the male and female reproductive organs. This key will allow researchers to identify to species minute pirate bugs from western North America, including currently unnamed species.
Objective 2: Significant progress was made on determining the upper and lower thermal limits of codling moth using differential scanning calorimetry. The immature stages completed are the egg, 4th and 5th instar, and the pupae. These thermal limits were used in ecological niche modeling papers for the world and China. The world maps were shared with both the industry and the United States Department of Agriculture-Animal and Plant Health Inspection Service (USDA-APHIS) to address concerns of apple importing countries in relation to the invasive potential of codling moth in their country. The model for China was developed to determine the stages of codling moth invasion, spread, and establishment in China to help develop control strategies to stem the spread of this destructive pest. Upon completion of the dataset, the values for the other immature stages will be used to modify, if needed, the current ecological niche maps.
Objective 3: Spinosad (Entrust) and spinetoram (Delegate) effects on kill and oviposition of western cherry fruit fly were determined by exposing 3-4, 7-10, or 14-18 day old flies to dry spinosad and spinetoram and untreated cherries or to insecticide-treated cherries at 15.6 degrees Centigrade (°C), 22.5°C, and 29.4°C to improve attract-and-kill approaches for western cherry fruit fly management. It was found that kill was not affected by fly age. Spinetoram killed more female flies by day 1 than spinosad at all temperatures. In both treatments, kill was lower at 15.6°C than 22.5°C and 29.4°C, although a difference between 22.5 and 29.4°C was detected more often in spinosad treatments. Both insecticides killed 3-4 day old flies quickly enough to prevent oviposition (the process of laying eggs), but neither prevented oviposition by 7-10 and 14-18 day old flies. Oviposition by flies exposed to spinosad and spinetoram did not differ at any temperature. Results indicate spinetoram is more toxic to flies than spinosad, but that higher toxicity is not needed to prevent oviposition by younger flies. Spineotoram residues are not sufficient to kill older flies quickly enough to reduce oviposition more than spinosad.
Studies were conducted to address several components needed to develop a successful, efficacious attract and kill approach for codling moth and leafrollers. Flight tunnel studies have compared the effectiveness of different trap liners with captured females to lure additional males to the trap. Studies were conducted to develop a liquid method to catch moths in bucket traps that combines the use of organic oil, vinegar, and propylene glycol. The interaction of several aromatic volatiles with the sex pheromones of leafrollers were evaluated. Mass trapping studies are currently in place in commercial orchards. Further field comparisons of volatile blends for codling moth and leafrollers are being investigated. Studies are also being conducted to characterize the volatiles released by various microbes that are both present in various host plants and in shoots damaged by aphids and leafroller larvae. The microbiome will be characterized, prominent species will be cultured and identified, and volatile emissions will be collected to develop new attractants for leafrollers.
Accomplishments
1. Identification of odorant receptors expressed in the abdomen tips of codling moth females. Odorant receptors are the key proteins involved in the insect sense of smell and study of these proteins has mainly focused on those expressed in antennae (the insect equivalent of our nose) which overlooks the other important odorant receptors. Scientists at the USDA-ARS Temperate Tree Fruit and Vegetable Research Unit in Wapato, Washington, and at the Swedish University of Agricultural Sciences, Alnarp, Sweden have used genomic technology to identify 39 odorant receptors expressed in female abdomen tips. Almost half of the odorant receptors identified in the abdomen tip are highly related to receptors in other insects that have been shown to respond to plant-derived semiochemicals, suggesting a potential role in oviposition site identification. The results produced in this study provide insights in how codling moth females locate host plants and egg-laying sites and may lead to more effective biorational control strategies against this insect pest.
2. Identified temperatures in waste piles deadly to apple maggot fly pupae. The apple maggot fly is a major quarantine pest of commercial apple in the U.S. Movement of plant waste containing apple maggot fly pupae to apple-growing areas for composting threatens the apple industry in Washington. ARS scientists in Wapato, Washington, determined whether heat in waste piles can kill pupae by placing pupae in small bags at different depths in ground plant waste piles covered with tarp insulation. Except near the bottom of piles during cold weather, all pupae exposed to heat in piles were killed. Results are important in that they show insulating ground plant waste piles is effective for killing apple maggot pupae. During cold periods, bottoms of piles may also need to be insulated to kill pupae near the ground, making the process more effective.
3. Efficacies of European cherry fruit fly traps. Western cherry fruit fly is a quarantine pest of cherries in western North America that is best detected using Yellow Sticky Strip (YSS) rectangle traps. Recently, the European cherry fruit fly invaded eastern North America, prompting surveys for it in the West. Sticky crossed-panel yellow Rebell and cylindrical-type yellow PALz traps were developed for this fly, raising the question of efficacies of these traps versus the YSS against western cherry fruit fly. ARS scientists in Wapato, Washington, determined the efficacies of the YSS versus Rebell and PALz traps baited with ammonia against western cherry fruit fly. The Rebell and YSS traps caught similar numbers of flies and more than the PALz trap. This result is important because it shows that the Rebell trap could be used to monitor western cherry fruit fly and suggests that the PALz trap is selectively better than the Rebell trap for surveys of European cherry fruit fly, as fewer western cherry fruit flies would clutter traps.
4. Reducing the emergence and survival of western cherry fruit fly. Western cherry fruit fly is a threat to the commercial cherry industry in the western U.S. The fly’s ability to survive in dry climates affects its distribution and pest status, but it is unclear if its survival rates are increased by irrigation in different soils. ARS scientists in Wapato, Washington, determined the effects of adding water to bare and grass-covered soils on survival rates of fly pupae in central Washington. Results showed that fly pupae survived equally well in irrigated and unirrigated bare soils but suffered relatively high mortality in unirrigated grass-covered soils. Results are important because they show that unirrigated, grass-covered soils or mulch barriers in mid- and late-summer could reduce fly survival, thus suppressing fly abundance.
5. Risk of global establishment of the European cherry fruit fly (ECFF). The European cherry fruit fly or Rhagoletis cerasi, is a highly destructive pest of cherries in Europe and Asia. The pest was recently detected in Canada and the U.S. for the first time. Its further expansion could threaten the tree fruit industry in the U.S., including the major cherry growing regions of Michigan, Washington, Oregon, and California. ARS scientists in Wapato, Washington, used ecological niche models to determine the risk of ECFF global establishment focusing on the major cherry growing regions of the U.S. Results show that under a no-irrigation scenario, the pest would establish in the East and West Coasts of the U.S; however, under an irrigation scenario, its distribution would expand to the major cherry-growing regions in the interior of central and eastern Washington and in California. Our results stress the importance of surveying for European cherry fruit fly to prevent its spread and establishment, both globally and particularly, in the U.S.
6. Phytoplasma alters flight behavior of pear psylla. Pear psylla is a key pest of pear and one of the most serious insect pest of pears because of its ability to develop resistance to insecticides and to vector the pathogen that causes pear decline. In the pear growing regions of the Pacific Northwest, nearly thirty percent of pear psylla harbor the plant pathogen Phytoplasma pyri, but the effects of Phytoplasma on pear psylla biology are not known. ARS scientists in Wapato, Washington, in collaboration with researchers at Heritage University in Toppenish, Washington, found that pear psylla infected with Phytoplasma are less likely to disperse from pear trees. By showing that Phytoplasma alters pear psylla flight behavior, these results will help elucidate patterns in psylla dispersal and colonization of pear orchards.
Review Publications
Yee, W.L. 2017. Temperature and food availability effects on spinosad and malathion against Rhagoletis indifferens (Diptera: Tephritidae) in the laboratory. Phytoparasitica. 45(5):673-682. https://doi.org/10.1007/s12600-017-0627-5.
Elmquist, D.C., Landolt, P.J., Ream, L.J., Cha, D.H. 2017. Laboratory demonstrations of pheromone-mediated scent-marking, orientation, and mounting behavior in Polistes exclamans Vienick (Hymenoptera: Vespidae). Annals of the Entomological Society of America. 111(1):21-30.
Neven, L.G., Kumar, S., Yee, W.L., Wakie, T. 2018. Current and Future Potential Risk of Establishment of Grapholita molesta (Lepidoptera: Tortricidae) in Washington State. Environmental Entomology. 47(2):448-456. https://doi.org/10.1093/ee/nvx203.
Wakie, T., Yee, W.L., Neven, L.G. 2018. Assessing the risk of global establishment of Rhagoletis cerasi (Diptera: Tephritidae), with emphasis on the United States. Journal of Economic Entomology. 111(3):1275-1284. https://doi.org/10.1093/jee/toy054.
Jaffe, B., Landolt, P.J. 2018. Field validation of a three chemical controlled release dispenser to attract codling moth (Cydia pomonella) (Lepidoptera: Tortricidae). Journal of Economic Entomology. 111(3):1268-1274. https://doi.org/10.1093/jee/toy045.
Tassin, M., Herrera, S., Knight, A.L., Barros-Prada, W., Contreras, E., Pertot, I. 2018. Volatiles of grape inoculated with microorganisms: Modulation of grapevine moth oviposition and field attraction. Microbial Ecology. https://doi.org/10.1007/s00248-018-1164-6.
Horton, D.R., Miliczky, E., Lewis, T.M., Cooper, W.R., Waters, T., Wohleb, C., Zack, R., Johnson, D., Jensen, A. 2018. New North American records for the Old World psyllid Heterotrioza chenopodii (Reuter) with biological observations (Hemiptera: Psylloidea: Triozidae). Proceedings of the Entomological Society of Washington. 120(1):134-152.
Gundersen, D.E., Adrianos, S.L., Allen, M.L., Becnel, J.J., Chen, Y., Choi, M.Y., Estep, A., Evans, J.D., Garczynski, S.F., Geib, S.M., Ghosh, S.B., Handler, A.M., Hasegawa, D.K., Heerman, M.C., Hull, J.J., Hunter, W.B., Kaur, N., Li, J., Li, W., Ling, K., Nayduch, D., Oppert, B.S., Perera, O.P., Perkin, L.C., Sanscrainte, N.D., Sim, S.B., Sparks, M., Temeyer, K.B., Vander Meer, R.K., Wintermantel, W.M., James, R.R., Hackett, K.J., Coates, B.S. 2017. Arthropod genomics research in the United States Department of Agriculture-Agricultural Research Service: Applications of RNA interference and CRISPR gene editing technologies in pest control. Trends in Entomology. 13:109-137.
Yee, W.L., Goughnour, R.B., Feder, J.L., Linn, C.E., Cha, D.H. 2017. Comparative responses of Rhagoletis zephyria and R. pomonella (Diptera: Tephritidae) to commercial and experimental sticky traps and odors in Washington State. Environmental Entomology. 46(6):1351-1358. https://doi.org/10.1093/ee/nvx130.
