Location: Temperate Tree Fruit and Vegetable Research
2019 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 likelihood 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
Under Objective 1, progress was made on improving knowledge of the behavior and ecology of winterform pear psylla. Many winterforms leave pear to overwinter on shelter plants and then return to pear in the spring. In fiscal year FY19, high-throughput sequencing of plant deoxyribonucleic acid (DNA) present in pear psylla guts was used to infer the landscape-level movements of winterform pear psylla. Work was also initiated using ribonucleic acid (RNA) sequencing to identify the genetic mechanisms for changes in behaviors among summerform, diapausing winterform, and post-diapause winterform pear psylla. This work is providing a better understanding of the biology, behavior, and landscape ecology of the winterform pear psylla, which will allow us to develop or improve management tactics that target this portion of the population.
Progress was made to determine factors that affect pupal mortality and adult emergence of western cherry fruit fly in the field. Immature stages of the fly overwinter as pupae in soil. The first year of the experiment determined that some soils are more conducive to pupal survival and adult fly emergence than others, but that soil moisture is needed for all soils to maximize survival. The second year of experimentation was initiated in FY19 and early-season results are now being tabulated to verify results from the first year.
The upper and lower thermal limits of codling moth, apple maggot and western cherry fruit fly were determined using differential scanning calorimetry and were compared to previously published phenology models for these species. The differential scanning calorimetry values agreed with the phenology models and showed that differential scanning calorimetry can be used to quickly identify thermal limits for a species, making identification of limits for newly invasive species quicker and easier to obtain. This knowledge of thermal limits can aid in determining the potential for invasive species to establish and spread in new environments.
Research continued from FY18 to characterize the role of putative odorant receptor genes in locating host plants and egg-laying sites. In addition, 40 neuropeptide/peptide hormone transcripts were identified using transcriptomes of the female abdomen tips, and research was initiated to characterize the roles of these genes.
Taxonomic examination was performed on minute pirate bugs collected from several poorly studied geographic regions, including rural areas in Montana and Oregon, agricultural regions in central Washington State, and desert regions in southern California. These collections allowed advances to be made in determining the species diversity of minute pirate bugs in North America and helped clarify host plant associations of certain poorly studied species of these insects. These advances will lead to a new and updated identification key for the North American fauna of this important group of predatory insects.
Subordinate projects related to Objective 1 include studies on Trechnites insidiosus, a parasitoid of pear psylla, and on predatory mites that attack pest spider mites. Work on Trechnites was initiated to compare trapping methods to monitor adult Trechnites populations and to correlate Trechnites population estimates with rates of parasitism of pear psylla. A Trechnites colony has also been created to determine pesticide non-target effects on this natural enemy; knowledge gained from this project will allow growers to make pesticide choices that minimally impact their Trechnites populations. Colonies of two species of predatory mites were established to support future work on pesticide non-target effects testing. Progress has also been made in assessing how gut contents of several predatory mite species changes throughout the season to better determine the role these organisms play in controlling pests in orchards.
Ecological niche models help identify environments where a species may establish and spread. This is important not only for newly invasive species, but for endemic species whose range may expand in response to climate change. Ecological niche models are only as accurate as the data used to train the program (machine learning). The addition of critical physiological parameters, such as upper and lower thermal limits, as well as the species distribution across different landscapes, can increase the accuracy and predictability of these models. In support of Objective 2, largescale landscape heterogeneity study for four important tree fruit pests – codling moth, oriental fruit moth, apple maggot, and western cherry fruit fly – was conducted in Washington State and underscored differences in habitat and landscape utilization among the four species. The landscape heterogeneity was also used to project the potential spread of these species in response to climate change. The strength of these models is that they can point out critical locations to concentrate pest control measures to stem the expansion of the distribution of these pests.
Laboratory and field experiments were initiated in support of Objective 3 to determine whether the artificial sweetener, erythritol, is lethal to pear psylla and other key pests of pear when applied to pear leaves.
Progress was made on determining temperature influences on the efficacy of the insecticides, spinosad and Delegate, for management of western cherry fruit fly. This was determined under laboratory conditions, as determining the influence of temperatures on insecticide effects in the field proved too difficult because larval infestations in cherries were non-existent, even in control trees in some years. Laboratory tests were completed and showed that under higher temperatures, flies were more active and killed more quickly by both materials applied on surfaces than at lower temperatures. However, more oviposition occurred at higher than lower temperatures.
In subordinate projects related to Objective 3, substantial progress was made toward developing attractive lures for monitoring and controlling paper wasps. Experiments were completed showing that the invasive European paper wasp is attracted to peony plants, and studies are underway to identify which peony compounds the wasps are attracted. A compound from the female sting apparatus of paper wasps was also found to be highly attractive to male wasps, and field experiments demonstrated that traps baited with the compound capture large numbers of wasps.
Accomplishments
1. Molecular gut content analysis of pear psylla. Pear psylla, the key insect pest of pears, occurs as two behavioral forms referred to as the summerform and winterform. The winter form of pear psylla is known to leave orchards in large numbers and overwinter on non-pear plants before recolonizing orchards in spring. ARS researchers in Wapato, Washington, in collaboration with scientists from Washington State University and Oregon State University, developed a method for gut content analysis of pear psylla and demonstrated that this method can be used to infer diets and landscape-level movements of psylla. Scientists then used this new tool to discover that the so-called non-dispersing summer stage of pear psylla, much like the winter behavioral form, is actually quite dispersive, and moves into habitats surrounding orchards in summer from which they then colonize new orchards. This unexpected finding must be acknowledged in predicting summer outbreaks of psylla in orchards and in evaluating spread of insecticide-resistant genotypes. Methods used in developing this new tool were published in a peer-reviewed journal, and that article was then featured in Entomology Today, a web-based publication of the Entomological Society of America which provides popularized or layperson accounts of new and interesting discoveries in entomology.
2. Three-dimensional versus rectangular sticky yellow traps for western cherry fruit fly. Western cherry fruit fly is a major quarantine pest of cherries in western North America that can be monitored using sticky yellow traps, but it is unclear which traps are best at detecting the fly. Personnel at ARS laboratory in Wapato, Washington, determined the effectiveness of three-dimensional versus rectangle yellow traps for catching the fly. It was found that a cross trap made of thin yellow plastic was more effective than a similar cross trap made of a thicker yellow plastic and yellow rectangles. Further work showed that its effectiveness was due to its large surface area and possibly its shade of yellow. Results are important in that the new cross trap could be an effective option or addition to rectangles for monitoring the fly.
3. New attractive lure to monitor and control paper wasps. Several species of Polistes paper wasps are significant pests when they swarm and aggregate on man-made structures in the southeastern U.S. Paper wasps use chemicals to communicate during these swarms, and identification of these chemicals may provide attractants that are useful for wasp control. ARS researchers in Wapato, Washington, Washington State University, and Department of Defense, found that paper wasps were attracted to a compound, N-3-methybutyl acetamide (MBA), emitted from the female wasp venom, and demonstrated that traps baited with MBA capture large numbers of wasps. This study shows that traps baited with MBA will be an effective tool to monitor and control paper wasps.
4. Potential establishment of spotted lanternfly in the world. Native to Asia, the spotted lanternfly is an emerging pest of many commercially important plants in Korea, Japan, and the U.S. Determining its potential distribution is important for developing proactive measures to protect commercially important commodities. ARS researchers in Wapato, Washington, used ecological niche modeling to predict highly suitable areas for spotted lanternfly in Asia, Oceania, South America, North America, Africa, and Europe, but also predicted that tropical habitats are not suitable for its establishment, contrary to published information. Within the U.S., the ecological niche modeling predicted that spotted lanternfly can establish in Pennsylvania, New Jersey, Virginia, West Virginia, Delaware, New York, Massachusetts, Rhode Island, New Hampshire, Connecticut, Maryland, Virginia, North Carolina, Kentucky, West Virginia, Ohio, Indiana, Michigan, Illinois, Iowa, Missouri, Kansas, California, Washington, and Oregon. If introduced, the spotted lanternfly is likely to establish in fruit-growing regions of the Pacific Northwest. Results of this study can be used by regulatory agencies to guide spotted lanternfly surveys and prioritize management interventions for this pest.
5. Eclosion and adult longevity traits of Rhagoletis tabellaria and Utetes tabellariae. Rhagoletis (R.) tabellaria is a fruit fly that attacks dogwood and has been implicated as a pest of some commercial fruit, but little is known of its biology. ARS researchers in Wapato, Washington, in collaboration with the University of Iowa, and the University of Notre Dame, determined the effects of chilling on emergence and longevity of R. tabellaria and its major parasitic wasp. When chilled, flies emerged earlier than wasps in accordance with when fly stages are available for attack. Although the parasite did not require chilling to complete development, R. tabellaria failed to emerge when not chilled, suggesting different physiological responses to cold by host and parasite. Flies survived longer than wasps in accordance with the short period when susceptible fly stages are available for attack. Results are important in that they expand our knowledge of Rhagoletis flies and their coevolution with their parasites.
6. Temperate and tropical/subtropical fruit use by apple maggot. The apple maggot fly is a threat to domestic and foreign fruit markets. This threat can be reduced through knowledge of host plant use by the fly. The apple maggot fly is a threat to domestic and foreign fruit markets. This threat can be reduced through knowledge of host plant use by the fly. ARS researchers in Wapato, Washington, in collaboration with Washington State University, determined the use of unmanaged (non-commercial) apple and hawthorn trees by the fly in Washington. The researchers surveyed various fruit for use by the fly and tested whether tropical and subtropical fruits are suitable for attack by the fly. They learned that several plants were recorded as new hosts and discovered that hawthorns were used more than unmanaged apple trees and most subtropical and tropical fruit were not suitable for the fly. Findings are important in that they could be useful for developing policies to protect both U.S. and subtropical fruit markets. These data have been added to the USDA-APHIS handbook on Fruit Flies.
7. Modeling abundance of two fruit flies in Washington State. Apple maggot and western cherry fruit fly are the two key quarantine pests of apples and cherries in Washington State. These flies are a threat to the tree fruit industry due to quarantine-related market restrictions. There is little quantitative information on where they are found, and what environmental factors affect the abundance of these flies. ARS researchers in Wapato, Washington, conducted a landscape heterogeneity study in which they determined that apple maggot is abundant in western Washington and less abundant in central and eastern Washington. In contrast, western cherry fruit fly is abundant in central and eastern Washington and less abundant in western Washington. Establishment of Low Pest Prevalence or Pest Free Areas are recommended in areas with zero or very low apple maggot abundance to allow the movement of apples without cold treatments. These data have been published in a peer-reviewed scientific journal and shared with the tree fruit industry, Washington Department of Agriculture, and USDA-Animal and Plant Health Inspection Service for assistance in negotiating export workplans and agreements for tree fruits from the Pacific Northwest.
8. Environmental effects on western cherry fruit fly diapause. There is a zero tolerance for the presence of western cherry fruit fly in commercially produced sweet cherries, and this pest has often been cited as a quarantine concern by current and perspective importers. ARS researchers in Wapato, Washington, assessed whether chilling duration, rearing temperature, humidity, and photoperiod influenced diapause completion and emergence of western cherry fruit fly. They determined that a chilling period of 15 weeks or greater is necessary to begin synchronous emergence of western cherry fruit fly, and that rearing temperature affected the timing of fly emergence. Photoperiod and humidity did not affect timing of emergence. These data can be used to determine whether western cherry fruit fly poses a threat to other countries importing sweet cherries from the Pacific Northwest.
Review Publications
Lane, J., Kumar, S., Yee, W.L. 2018. Modeling the climatic suitability for Fopius arisanus (Hymenoptera: Braconidae) and its host fly Bactrocera dorsalis (Diptera: Tephritidae). Journal of Economic Entomology. 154(1):65-78. https://doi.org/10.31184/M00138908.1541.3909.
Tadeo, E., Muniz, E., Rull, J., Yee, W.L., Aluja, M., Lasa, R. 2017. Development of a low-cost and effective trapping device for apple maggot fly (Diptera: Tephritidae) monitoring and control in Mexican commercial hawthorn groves. Journal of Economic Entomology. 100(4):1658-1667. https://doi.org/10.1093/jee/tox167.
Zhu, H., Kumar, S., Neven, L.G. 2017. Codling moth establishment in China: Stages of invasion and potential future distribution. Journal of Insect Science. 17(4):85. https://doi.org/10.1093/jisesa/iex054.
Yee, W.L. 2018. Efficacies of Rhagoletis cerasi traps and ammonium lures for Western Cherry Fruit Fly (Diptera: Tephritidae). Journal of Insect Science. 18(3):14. https://doi.org/10.1093/jisesa/iey054.
Yee, W.L. 2018. Spinosad versus Spinetoram effects on kill and oviposition of Rhagoletis indifferens (Diptera: Tephritidae) at differing fly ages and temperatures. Journal of Insect Science. 18(4):15. https://doi.org/10.1093/jisesa/iey082.
Yee, W.L., Chapman, P.S. 2018. Irrigation and grass cover effects on pupal survival rates in soil and adult emergence patterns of Rhagoletis indifferens (Diptera: Tephritidae). Environmental Entomology. 47(2):457-466. https://doi.org/10.1093/ee/nvx209.
Cooper, W.R., Horton, D.R., Wildung, M., Jensen, A., Thinakaran, J., Rendon, D., Nottingham, L., Beers, E., Wohleb, C., Hall, D.G., Stelinski, L. 2019. Host and non-host whistle stops by psyllids: Molecular gut content analysis by high-throughput sequencing reveals landscape-level movements by Psylloidea (Hemiptera). Environmental Entomology. 48(3):554-566. https://doi.org/10.1093/ee/nvz038.
Knight, A.L., Stewart, W.L., Basoalto, E. 2018. Importance of trap liner adhesive selection for male moth catch (Lepidoptera: Tortricidae) with bisexual attractants. Journal of Applied Entomology. 142(8):731-744. https://doi.org/10.1111/jen.12528.
Knight, A.L., Light, D.M. 2018. Pear ester - from discovery to delivery for improved codling moth management. In: Beck, J., Rering, C.C., Duke, S.O., editors. Roles of Natural Products for Biorational Pesticides in Agriculture. Washington, D.C.: ACS Publications. p. 83-113. https://doi.org/10.1021/bk-2018-1294.ch008.
Judd, G., Knight, A.L. 2017. Trapping female Pandemis limitata (Lepidoptera: Tortricidae) moths with mixtures of acetic acid, benzenoid apple leaf volatiles, and sex pheromones. The Canadian Entomologist. 149(6):813-822. https://doi.org/10.4039/tce.2017.38.
Judd, G., Knight, A.L. 2017. Developing kairomone-based lures and traps targeting female Spilonota ocellana (Lepidoptera: Tortricidae) in apple orchards treated with sex pheromones. The Canadian Entomologist. 149(5):1-15. https://doi.org/10.4039/tce.2017.37.
