Research Project: Integrated Approach to Manage the Pest Complex on Temperate Tree Fruits

Location: Temperate Tree Fruit and Vegetable Research

2022 Annual Report

Objectives
The long-term objective of this project is to provide the basic and applied information needed for the development and transfer of safe and environmentally sustainable tools or methods for management of arthropod pests of temperate tree fruits. Specifically, during the next five years we will focus on the following objectives: Objective 1: Develop and improve tools and approaches for early detection, prediction, and monitoring of arthropod pests and their natural enemies in temperate tree fruits. • Sub-objective 1A: Determine if pre-harvest commercial pear is an acceptable host for apple maggot fly. • Sub-objective 1B: Identify volatile attractants from pear trees for early detection of orchard-colonizing winterform pear psylla. • Sub-objective 1C: Identify the primary non-orchard habitats that are sources of orchard-colonizing winterform pear psylla. • Sub-objective 1D: Identify the thermal tolerances of brown marmorated stinkbug and Trissolcus japonicus to more accurately determine potential establishment and spread. Objective 2: Provide basic and applied information of the physiology, biochemistry, behavior, and landscape ecology of arthropod pests and their natural enemies necessary to develop new or improve existing integrated pest management strategies in temperate tree fruits. • Sub-objective 2A: Determine the thermal kinetics of apple maggot. • Sub-objective 2B: Determine functions of proteins key to codling moth reproduction, development, physiology, and behavior. • Sub-objective 2C: Determine extent of cryptic species diversity in minute pirate bug fauna of the western U.S. in both orchard and non-orchard habitats. • Sub-objective 2D: Examine non-target effects of herbicides on key natural enemies of arthropod pests of apple and pear. Objective 3: Develop new or improved integrated management strategies to control arthropod pests in temperate tree fruits. • Sub-objective 3A: Improve control strategies for apple maggot in organic waste. • Sub-objective 3B: Develop pest management strategies for cherry fruit fly that incorporate newer and less toxic insecticides. • Sub-objective 3C: Model the relationship between estimated populations of Trechnites adults and rates of parasitism of pear psylla. • Sub-objective 3D: Develop management practices that increase the retention time of released natural enemies of arthropod pests of apple.

Approach
Objective 1. Sub-objective 1A: Behavioral and development bioassays will determine if pear is an acceptable host for apple maggot and whether pear fruit is a potential source for apple maggot introduction in export countries. Subobjective 1B: Volatiles will be identified from pear trees using GC-MS, and electroantennogram, behavior assays, and field trials will determine whether isolated volatiles elicit responses from pear psylla. The resulting lure will be used to monitor pear psylla populations. Sub-objective 1C: Gut content analysis will be used to where pear psylla overwinter. Sub-objective 1D: Differential scanning calorimetry will be used to determine the thermal capacity of brown marmorated stink bug and its parasitoid, and to identify climates that are favorable to their establishment and spread. Objective 2. Sub-objective 2A: The thermal death kinetics of apple maggot will be determined using differential scanning calorimetry and micro-respiration. Results will be used to improve management of apple maggot in commercial composting facilities located in apple maggot free zones. Sub-objective 2B: Candidate codling moth genes will be silenced using CRISP-Cas9 and behavior assays will be used to identify the function of the silenced genes. Results will identify viable gene-targets for use in codling moth control. Sub-objective 2C: Morphology of Orius will be examined to identify diagnostic traits and to possible new species, and a diagnostic key will be developed to identify species belonging to the group of important natural enemies. Sub-objective 2D: Standard laboratory bioassays will be used to examine the effects of herbicides and additives on mortality and fecundity of the key orchard predators Galendromus occidentalis, Amblydromella caudiglans, and the European earwig. Results of this study will allow growers to adapt orchard floor management strategies that conserve key natural enemies. Objective 3. Sub-objective 3A: Laboratory experiments will be conducted to determine whether 100% of apple maggot flies are killed by exposure to 55 degrees, the temperature found in commercial composting operations. Sub-objective 3B: Standard bioassays will be used to determine whether the insecticides tolfenpyrad, pyrifluquinazon, azadirachtin, and pyrethrins kill or reduce fecundity of cherry fruit fly and can be used as an alternative to spinosad as an attract and kill approach to fruit fly management. Sub-objective 3C: Adult populations of Trechnites will be monitored using traps and psylla parasitism rates will be monitored by dissection of psylla or by PCR and the relationship between adult populations of Trechnites and actual parasitism rates will be modeled to allow growers to incorporate biological control provided by Trechnites in psylla management practices. Sub-objective 3D: Field studies will be conducted in commercial apple orchards to test whether nutritional supplements including Typha spp. pollen or brine shrimp cysts increase the retention of released natural enemies, Orius insidiosus, Chrysoperla rufilabris, or Cryptolaemus montrouzieri. Results will improve augmentative biological control in commercial orchards.

Progress Report
Substantial progress was made on all three objectives with the overall goal to develop biorational management of insect pests of temperate tree fruits. The goal of Objective 1, which has four sub-objectives, is to develop or improve tools and approaches for early detection, prediction, or monitoring of tree fruit pests with a focus on apple maggot, pear psylla and brown marmorated stink bug. In support of Sub-objective 1A, experiments to test whether pre-harvest pear fruit is susceptible to attack by apple maggot suggested that unripe pears are susceptible to attack by flies under laboratory conditions. Lack of reports of apple maggot infesting pears under field conditions is therefore due to factors other than fruit hardness. Under Sub-objective 1B, volatiles were collected from pear trees beginning early February when the trees were dormant through the end of March following budbreak. This period corresponds with the colonization of pear orchards by overwintered pear psylla. Volatiles captured from pear trees are being identified and quantified using gas-chromatography mass spectrometry. The compounds will be used throughout the year to identify which compounds elicit responses from pear psylla. This information will be used to develop a lure to help monitor the arrival of overwintered pear psylla in pear orchards in early spring. For Sub-objective 1C, pear psylla were collected in early spring as they were recolonizing orchards from their winter shelter plants. Gut content analysis will be used to identify the dietary history of the psylla and the shelter plants on which pear psylla primarily overwinter. Experiments under Sub-objective 1D were completed, and a manuscript is being prepared to predict the limits of geographical expansion and colonization by brown marmorated stink bug. Progress was also made on several subordinate projects related to Objective 1. Several new compounds were identified from the venom reservoir of the invasive Asian giant hornet. Lures were made from to mimic the hornet’s alarm pheromone or prey. These lures are being field-tested in Washington where the hornet is invasive, and in the hornet’s native range in Asia. Laboratory experiments were also conducted to identify optimal trap designs for hornet capture. Results will help efforts to eradicate or manage Asian giant hornet in Washington and circumvent threats to the honeybee and tree fruit industries. In another subordinate project related to Objective 1, leafhopper vectors of x-disease phytoplasma were collected from diseased orchards throughout Washington and were tested for the presence of phytoplasma. The DNA samples were processed for gut content analysis to identify weedy sources of phytoplasma-infected leafhopper vectors. The goal of Objective 2 and its four sub-objectives is to provide information on the basic biology of tree fruit pests and their natural enemies. Experiments under Sub-objective 2A were completed, and a manuscript is being prepared to document lethal temperatures for apple maggot, which will be used to develop treatments to kill apple maggot in commercial composting facilities located in apple maggot free zones. In support of Sub-objective 2B, complete assessments have been made of odorant receptor gene expression patterns in codling moth female abdomen tip and ovipositor. Replicated findings indicate differences in odorant receptor expression in mated versus non-mated females. Results from these experiments will provide guidance on functional assays of specific receptor proteins. Gene editing experiments have been initiated to disable a single odorant receptor that is present in female codling moth antennae and abdomen tip but is not found in males. Initial genotyping evaluations indicate that editing has been successful. Current efforts are focused on establishing colonies with the odorant receptor deletion genotype. Experimental studies are being designed and will be conducted to assess the role on this odorant receptor on female codling moth olfactory behavior. Collectively, this knowledge will ultimately inform the development of sustainable integrated pest management strategies aimed at controlling codling moth damage in fruit orchards. In support of Sub-objective 2C, a first draft of a key to the minute pirate bugs (Orius spp.) of North America and Mexico was completed that includes the three known species of North American Orius plus six species that are as yet undescribed. Patterns among species in color, size, anatomical traits, geography, and plant associations are being used to separate species. The ultimate goal of this sub-objective is to formally name the undescribed species and to publish an identification key that will allow entomologists and biological control workers to discriminate among the nine species of this important complex of natural enemies. Nearly all experiments related to Sub-objective 2D have been completed, and manuscripts are being prepared to document the non-target effects of herbicides and adjuvants on orchard predators and to provide growers with knowledge to select pesticide spray practices that best conserve of beneficial arthropods. Subordinate projects related to Objective 2 were conducted to document the biology and life-history of Trechnites, an important parasitoid of pear psylla. Experiments were conducted to test the non-target effects of orchard pesticides on Trechnites to allow growers to select pesticides that can be used in combination with conservation biocontrol. Several psyllid parasitoids were found attacking non-pest psyllids related to pear psylla, but it remains uncertain whether these parasitoids will also attack pear psylla. Gut content analysis was used to identify plant resources used by Trechnites, and data are currently being analyzed. Lastly, Trechnites was found to harbor the bacterial endosymbiont, Wolbachia, which causes reproductive manipulations in insects and can improve the ability for some parasitoids to control pests. Wolbachia was less prevalent in southern versus northern latitudes. Another subordinate project Objective 2 identified from DNA sequence data several parasitoid flies and pathogens that attack leafhopper vectors of x-disease. Lastly, collaborative research was initiated to determine if pear trees that are exposed to chemical defense elicitors release volatile compounds that induce defenses in neighboring trees. The goal of Objective 3 and its four sub-objectives is to develop new or improved integrated pest management strategies to control arthropod pests in temperate tree fruits. In support of Sub-objective 3A, experiments were completed to test various heat regimes on apple maggot mortality and identified temperatures that kill 100% of apple maggot fly pupae in composting yard waste. In support of Sub-objective 3B, organic pyrethrin insecticides were mixed with a hydrophobic, organic coating to determine their efficacy in killing and preventing oviposition by western cherry fruit fly. The mixture of the two materials eliminated fly oviposition in cherries in laboratory trials. In support of Sub-objective 3C, the final year of sampling for the parasitoid Trechnites and its host pear psylla was completed. Data are being used to model relationships among pear psylla population densities, Trechnites abundance, time of year, and grower management records. These models will allow growers to adopt management practices that best conserve this parasitoid. Under Sub-objective 3D, experiments are being conducted in commercial orchards to test releases of the predators called mealybug destroyers for control of mealybugs. Progress was also made on subordinate projects related to Objective 3. Analysis of data from the previous reporting cycle indicated that releases of lacewings, important generalist predators, effectively reduced aphid populations in orchards. Work is continuing to determine the best methods for lacewing releases. Initial experiments were completed to develop protocols for removing earwigs from soft fruit orchards where they are pests and releasing them in pear and apple orchards where they are predators of aphids and psyllids. Results indicate that cardboard roll traps are the best method for catching and moving earwigs, and removal of earwigs reduced damage in apricot while releasing them in apple and pear moderately decreased pest abundance.

Accomplishments
1. Comprehensive description of pesticide non-target effects on a “new” predatory mite. Conservation of predatory mites that eat pest mites forms the cornerstone of integrated mite management in Washington apple. Prior research found that a predatory mite that was once uncommon in apples is now present in many orchards. Growers needed to know which orchard pesticides are harmful to the predatory mite so they can choose pesticides that control target pests without killing the predatory mite. ARS researchers in Wapato, Washington, and Washington State University scientists, tested 11 insecticides, nine miticides, four fungicides, seven herbicides, and five adjuvants for compatibility with the predatory mite. The researchers then categorized the pesticides as low, moderate, or high in terms of harm to the predator. Growers can now use this information to conserve the “new” predatory mite when making spray decisions.

2. Gene editing of female-specific codling moth odorant receptor. The codling moth is the most prominent insect pest of apple in the state of Washington. The sense of smell has great influence on codling moth behavior. Scientists in the past have successfully targeted codling moth sense of smell to manipulate their behavior and reduce codling moth damage in the apple orchards. Current research on the genetics of the codling moth sense of smell aims to increase knowledge on codling moth biology and improve pest management. ARS researchers in Wapato, Washington, utilized gene editing to disrupt a gene involved in codling moth sense of smell that is functional in female moths, but not in males. In future research, they will conduct studies with these genetically edited moths to determine how the disrupted gene influences behaviors of female codling moths.

3. Pyrethrin combined with an organic, food-grade coating protects cherries against western cherry fruit fly. Western cherry fruit fly is a quarantine pest of sweet cherries in western North America, where there is zero tolerance for fly-infested fruit. Organic control options for the fly are limited, and new management tools are urgently needed. ARS researchers in Wapato, Washington, and scientists at Lincoln University in Lincoln, New Zealand, determined the effects of combining organic insecticides (pyrethrins) with an organic, hydrophobic food-grade coating on egg laying by the western cherry fruit fly. They found that the combination of these two organic products reduced egg laying by flies in cherries nearly 100% more than using pyrethrins alone. These results provide cherry farmers a new organic-based method to control the western cherry fruit fly.

4. Heat treatments for killing apple maggot in organic yard waste. Apple maggot fly is a key quarantine pest of apple. Washington imposes strict guidelines on movement of apple maggot-infested materials to exclude this pest from apple growing regions of the state. Movement of apple maggot to fly-free regions occurs by transportation of yard waste from western Washington to commercial composting facilities in eastern Washington. ARS researchers in Wapato, Washington, and Engineered Compost Systems in Seattle, Washington, developed heat treatments to kill 100% of apple maggots in imported yard waste. Government agencies are now using this information to develop protocols to eliminate the movement of apple maggot in organic waste to fly-free apple growing regions of Washington.

5. Identification of stink bug salivary proteins and their potential role in disarming plant defenses. Stink bugs are notorious pests of crops that inject saliva into plants while they feed. Stink bug saliva has roles in digestion of plant tissues, but little is known about other possible roles. ARS researchers in Wapato, Washington, and Washington State University scientists, identified salivary proteins of five stink bug including two important invasive species, the brown marmorated stink bug and southern green stink bug, and three native pest species. The researchers identified numerous salivary proteins that potentially disarm plant defenses, allowing the insects to feed on a diversity of crop hosts. This study will help the researchers better understand how stink bugs avoid plant defenses and to develop crops that are resistant to stink bug pests.

6. eDNA technology to identify invasive species in green yard waste. As metropolitan areas grow, the sites where municipal waste can be sent and treated have become overwhelmed and cannot accept more waste. Therefore, many urban areas seek out new landfills to accept and treat municipal waste, often in rural locations where agriculture is a primary enterprise. A component of municipal waste is green yard waste, which may contain pests that could adversely impact agriculture near rural landfills. ARS researchers in Wapato, Washington, in collaboration with researchers at the University of British Columbia, Canada, developed a method called eDNA technology to detect invasive species in green yard waste. The method uses high-throughput sequencing to detect DNA signatures of the invasive species. This information will be useful in determining the risk of the introduction of invasive species to rural areas where landfills handle municipal waste containing green yard waste.

7. Discovery of new psyllid–parasite associations. Pear psylla is attacked extensively in Europe and to a lesser extent in North America by two parasitoids in the genus Prionomitus. While host records other than pear psyllids are well-known for these two parasites in Europe, little is known about which psyllid hosts are used by North American populations of the parasites. Non-pest psyllids in Europe help the parasites retain residency in pear growing regions by being hosts when pear psylla is not available. ARS researchers in Wapato, Washington, collected psyllids from native plant species of Washington State and allowed parasites to emerge from the insects. Both species of Prionomitus were found to parasitize native psyllids, including species not previously known to be attacked by Prionomitus in North America. These findings identify non-pest psyllid species in North America that are reservoirs of parasites that attack pear psyllids in Europe and North America.

8. Effects of winter length on fruit flies and their Braconid parasitoids. Fruit flies are major pests of fruits that are often attached by parasitoid wasps. Climate change and warming trends could upset the timing of life history events of flies and their wasp parasites and impact the contribution to fruit fly management provided by the parasitoids. A multi-state team of researchers that included ARS scientists in Wapato, Washington, determined the effects of simulated short and long winter lengths on the timing of fly emergence. Results suggest that the sensitivity of flies to winter cold length as measured by emergence timing is greater than that of wasps, while the sensitivity of wasps to warm summer conditions is greater than that of flies. The results suggest that global warming could have potentially significant evolutionary and biocontrol consequences for fruit flies.

9. Reverse ecological niche modeling, a new approach for predicting environmental suitability for invasive species. Determining the potential geographic distribution of every invasive pest for control efforts using current predictive modeling approaches is impractical because there are so many individual species. ARS researchers in Wapato, Washington, and APHIS researchers in Riverdale, Maryland, developed a new method called the reverse ecological niche modeling approach for predicting species distributions that does not require analyzing individual species. Results using this approach successfully predicted regions of the world that are climatically similar, showing that if species are introduced from environmentally similar areas to an area of interest, the probability of establishment there is very high. Results are important in that they introduce a novel tool for predicting the establishment of invasive species that may be useful for fundamental ecologists and regulatory agency personnel.

10. Description of thermal niche of brown marmorated stink bug. Brown marmorated stink bug BMSB) is an invasive species that causes injury to tree fruits. The potential of this species to establish and spread in a new environment is largely dependent upon the species tolerance to temperature extremes experienced in the new area. ARS researchers in Wapato, Washington, determined the lower, upper thermal limits of all life stages of BMSB as well as identifying the optimal temperature range for growth and development. The third instar was found to be the most thermotolerant of all the life stages. The optimal range of temperatures for growth and development was determined to be between 10 to 25 degrees C, Thermal stress was observed at temperatures between 30 and 35 degrees C, while all life stages exhibited thermal death between 35 and 40 degrees C. This information will be used in the development of modified ecological niche models to help predict the spread of the species as well as the potential effects of climate change.

Review Publications
Yee, W.L. 2021. Tolerances of apple maggot (Diptera: Tephritidae) larvae and different age puparia to water flotation and immersion. Environmental Entomology. 50(6):1407-1415. https://doi.org/10.1093/ee/nvab102.
Revadi, S.V., Gianuzzi, V., Rossi, V., Hunger, G.M., Conchou, L., Rondoni, G., Conti, E., Anderson, P., Walker III, W.B., Jacquin-Joly, E., Koutroumpa, F., Becher, P.G. 2021. Stage-specific expression of an odorant receptor underlies olfactory behavioral plasticity in Spodoptera littoralis larvae. BMC Biology. 19. Article 231. https://doi.org/10.1186/s12915-021-01159-1.
Chen, X., Kaur, N., Horton, D.R., Cooper, W.R., Qureshi, J.A., Stelinski, L.L. 2021. Crude extracts and alkaloids derived from Ipomoea-Periglandula symbiotic association cause mortality of Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae). Insects. 12(10). Article 929. https://doi.org/10.3390/insects12100929.
Serrano, J.M., Landolt, P.J., Reyes Corral, C.A., Millar, J.G. 2022. Sex pheromones and sex attractants of species within the genera Idolus Desbrochers des Loges and Dalopius Eschscholtz (Coleoptera: Elateridae) in the western United States. Agricultural and Forest Entomology. 24(3):301-309. https://doi.org/10.1111/afe.12494.
Cooper, W.R., Marshall, A.T., Foutz, J., Wildung, M.R., Northfield, T.D., Crowder, D.W., Leach, H., Leskey, T.C., Halbert, S.E., Snyder, J. 2022. Directed sequencing of plant specific DNA identifies the dietary history of four species of Auchenorrhyncha (Hemiptera). Annals of the Entomological Society of America. 115(3):275-284. https://doi.org/10.1093/aesa/saab053.
Millar, J.G., Williams Iii, L., Serrano, J.M., Halloran, S., Grommes, A.C., Huseth, A.S., Kuhar, T.P., Hanks, L. 2022. A symmetrical diester as the sex attractant pheromone of the North American click beetle Parallelostethus attenuates (Say) (Coleoptera: Elateridae). Journal of Chemical Ecology. 48;598-608. https://doi.org/10.1007/s10886-022-01360-8.
Bruzzese, D.J., Schuler, H., Wolfe, T.M., Glover, M.M., Mastroni, J., Doellman, M.M., Tait, C., Yee, W.L., Rull, J., Aluja, M., Hood, G.R., Goughnour, R., Stauffer, C., Nosil, P., Feder, J.L. 2021. Testing the potential contribution of Wolbachia to speciation when cytoplasmic incompatibility becomes associated with host-related reproductive isolation. Molecular Ecology. 31(10):2935-2950. https://doi.org/10.1111/mec.16157.
Orpet, R., Cooper, W.R., Beers, E.H., Nottingham, L.B. 2021. Test of plant defense elicitors for arthropod pest suppression and PR-1 gene induction in pear orchards. Entomologia Experimentalis et Applicata. 169(12):1137-1146. https://doi.org/10.1111/eea.13110.
Schmidt-Jeffris, R.A., Beers, E.H., Sater, C. 2021. Meta-analysis and review of pesticide non-target effects on phytoseiids, key biological control agents. Pest Management Science. 77(11):4848-4862. https://doi.org/10.1002/ps.6531.
Schmidt-Jeffris, R.A., Moretti, E.A., Bergeron, P.E., Zilnik, G.L. 2021. Nontarget impacts of herbicides on spiders in orchards. Journal of Economic Entomology. 115(1):65-73. https://doi.org/10.1093/jee/toab228.
Farfan, M.A., Coffey, J., Schmidt-Jeffris, R.A. 2021. Evaluation of Tarsonemus bilobatus and Podosphaera xanthii as suitable resources for Proprioseiopsis mexicanus in cucurbit systems in the Southeast USA. Experimental and Applied Acarology. 85:31-40. https://doi.org/10.1007/s10493-021-00658-8.
Yee, W.L., Forbes, A.A., Feder, J.L. 2021. Contrast in post-chill eclosion time strategies between two specialist braconid wasps (Hymenoptera: Braconidae) attacking rhagoletis flies (Diptera: Tephritidae) in western North America. Environmental Entomology. 50(5):1173-1186. https://doi.org/10.1093/ee/nvab080.
Neven, L.G., Wakie, T.T., Yee, W.L. 2021. The eclosion of Rhagoletis pomonella (Diptera: Tephritidae) under different chill durations and simulated temperate and tropical conditions. Environmental Entomology. 50(3):706-712. https://doi.org/10.1093/ee/nvab018.
Yee, W.L., Kaiser, C. 2022. Evaluation of organic, food-grade hydrophobic coatings for suppressing oviposition and increasing mortality of western cherry fruit fly (Diptera: Tephritidae). Environmental Entomology. Article nvac033. https://doi.org/10.1093/ee/nvac033.