Location: Temperate Tree Fruit and Vegetable Research
2020 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
This is the final report for project 2092-22430-002-00-D, “New Technologies and Strategies to Manage the Changing Pest Complex on Temperate Tree Fruits,” which is set to expire on October 25, 2020. The project was subject to substantial personnel changes including 3.5 scientist vacancies with expertise in chemical ecology, biological control, and insect genetics, and one new scientist hired with expertise in biological control. Progress was made for all 3 objectives despite these critical vacancies.
In support of Objective 1, research was conducted to improve knowledge of behavior, physiology, ecology, and biochemistry of key insect pests - brown marmorated stink bug, pear psylla, western cherry fruit fly, Asian giant hornet, and codling moth - and their key natural enemies.
Reserch on Sub-objective 1A focused on the Brown marmorated stink bug which was recently introduced to the Pacific Northwest. Natural and suburban vegetation was sampled to monitor the spread of this invasive insect in eastern Washington. Distributions remained primarily urban during the sampling period, while most stink bugs present in non-agricultural areas were collected from succulent or fruiting plants. Native stink bugs collected during these surveys were catalogued to provide a resource for examining how the invasion of brown marmorated stink bug impacts native insect populations.
Additional research on Sub-objective 1A focused on developing greater knowledge of the overwintering biology of pear psylla with the goal of better managing early-season infestations. A method was developed to identify the dietary history of psylla by sequencing plant DNA found in the insect’s gut. This information can then be used to identify which non-crop shelter plants are most likely to be sources of overwintered pear psylla arriving in orchards in early spring. This method is being adapted to study the landscape-movements of leafhopper vectors of X-disease phytoplasma and provided justification for an objective of the new project plan. In a subordinate project, changes in transcriptome-wide gene expression are being analyzed to better understand the genetic basis and timing for changes in pear psylla biology occurring during winter and spring.
For Sub-objective 1B, research focused on the identification of attractants for generalist natural enemies which would enable the development of lures to attract predators to infestations within orchards. Research was initiated to determine whether volatiles emanating from microbial species growing on the honeydew of aphids are attractive to natural enemies. Field surveys revealed at least 40 bacterial species within 16 genera growing on aphid honeydew in apple and pear orchards, and that several species of parasitoid wasps were attracted to volatiles produced by these bacteria.
For Sub-objective 1C, research focused on the Western cherry fruit fly, a major pest of cherry, which develops within fruit but pupates in soil. Research assessed the ability of the western cherry fruit fly to survive in dry soils and showed that fly pupae survived equally well in irrigated and unirrigated bare soils but suffered relatively high mortality in unirrigated grass-covered soils. These results suggest that unirrigated, grass-covered soils or mulch barriers in mid- and late-summer could reduce fly survival, thus suppressing fly abundance. A related study is examining the effects of irrigation and soil composition on survival of western cherry fruit fly pupae. Results are showing that variations in sand, silt, and clay can impact when and how many western cherry fruit flies emerge. Collectively, these results will allow researchers to better predict the types of habitats and climates that are most susceptible to infestation by western cherry fruit fly.
Sub-objective 1D continued to evaluate the upper and lower thermal limits of all developmental stages of the codling moth, apple maggot, and western cherry fruit fly which were determined using differential scanning calorimetry.
In support of Sub-objective 1E, research continued to investigate the function of codling moth genes, which is challenging due to the ineffectiveness of standard methods for functional genomics of moths. A CRISPR-Cas9 genome editing system was developed for codling moth to study protein function. After optimizing this system by editing a male dosage compensation protein gene, the tool was used to study the function of an odorant receptor gene used by males to locate females for mating. Unexpectedly, the knock-down of this odorant receptor in females caused mated females to lay unviable eggs. Subsequent experiments showed that this odorant receptor, which was previously only known to be expressed in male antennae, was also expressed in the female abdomen tip. These results suggest that this odorant receptor has a previously unknown role in signaling to females that they have mated. The validation of CRISPR-Cas9 gene editing tool for codling moth provided justification for an objective in the new project plan.
For Sub-objective 1F, morphological, behavioral, and molecular genetic techniques were used to show that the minute pirate bug complex in western North America includes four described native species and six previously unknown species. The morphological data were used to develop a dichotomous key for identifying described and undescribed species. Field-collecting of specimens from multiple geographic regions combined with examination of over 3,000 museum-housed specimens was used to develop distribution maps based upon over 600 unique geographic records. These data were used to define each species’ known current distribution in western North America. Geographic and biological data, combined with the dichotomous key, provide growers and pest control advisors the tools needed to identify species of minute pirate bugs common in orchards of western North America. That information in turn will allow growers to more effectively incorporate biological control considerations into pest management decisions.
In a subordinate project related to Objective 1, trapping methods were tested to monitor adult Trechnites populations and methods for detecting cryptic parasitoids were developed. Work was initiated to correlate adult population estimates with parasitism rates of pear psylla using these new methods. A method developed for obtaining large numbers of Trechnites from orchards will assist future work to determine pesticide non-target effects on Trechnites and improve pest management decisions. This research provided the basis for an objective in the new project plan. Other related subordinate projects compared non-target effects of common insecticides, fungicides, and acaricides on two predatory mites and used gut content analysis to evaluate seasonal changes in dietary breadth of predatory mites. In yet another subordinate project, studies were initiated to identify attractants for the newly introduced Asian giant hornet and to develop tools to detect and monitor the spread of this pest.
In support of Sub-objective 2B, research was conducted to improve ecological niche models used to determine the limits to establishment and spread of quarantined insect pests. In a subordinate project, ecological niche modeling for 16 species of tree fruit pests of potential risk for movement from Canada to Washington via transport of municipal green waste revealed that several of these pests pose a significant risk to establish and spread in central Washington. These data will aid USDA-Animal Plant Health Inspection Service and Washington State Department of Agriculture in establishing guidelines for proposed shipments of municipal waste from Canada to the United States.
For Objective 3, research was conducted to develop and improve use of alternatives to conventional pesticides.
Sub-objective 3A focused on identifying volatile compounds that would be attractive to both sexes of moths and lead to the development of an effective attract and kill approach. Lures emitting plant-based kairomones that are highly attractive to both sexes of codling moth and leafrollers were developed and are a being tested by private companies for use in attract and kill management approaches.
Sub-objective 3B evaluated three commercially available natural enemy food product supplements (Typha pollen, brine shrimp cysts, and Ephestia kuehniella eggs) were tested as potential food supplements for two predatory mite species. Initial results provided a foundation for an objective of the new project plan to devise ways to retain predators within orchards.
Sub-objective 3C examined whether temperature alters the efficacy of the insecticides spinosad and Delegate for management of western cherry fruit fly. Results of laboratory assays were mixed and showed that the increased activity of western cherry fruit fly at higher temperatures caused them to be killed more quickly by both insecticides, but also resulted in greater oviposition rates. In contrast, the efficacy of the conventional pesticide, malathion, was not affected by temperature. The management of western cherry fruit fly could be improved by using increasing rates of spinosad or Delegate with increasing temperatures.
For Sub-objective 3D, laboratory and field studies showed that several commercially available elicitors of acquired plant defenses reduce populations of pear psylla suggesting that the use of these elicitors for management of fire flight may also contribute to the management of pear psylla. Results from a subordinate project demonstrated that foliar applications of the alternative dietary sweetener, erythritol, deters settling and oviposition by pear psylla and reduces pear psylla survival. Erythritol also caused increased mortality of mite pests but had negative non-target effects on a predatory mite. These findings show that erythritol could be developed into a safe and effective tool for insect management.
Accomplishments
1. Identifying diagnostic genetic markers for cryptic invasive agricultural pests. The apple maggot fly is an important quarantine pest of apples in the Pacific Northwest of the United States that is monitored using traps. The similar-looking snowberry maggot fly is frequently caught on these traps and can be mistaken for apple fly, which could lead to unjustified quarantines. Researchers at the USDA laboratory in Wapato, Washington, in collaboration with researchers at the University of Notre Dame, Indiana, Wayne State University, Detroit, Michigan, and McGill University, Canada, developed inexpensive, quick and reliable methods for discriminating the two fly species. A simple and cost-effective diagnostic approach using Illumina sequencing of double digest restriction-site associated DNA markers was developed. In addition, a diagnostic test based on agarose gel electrophoresis of restriction enzyme-digested polymerase chain reaction amplification products was able to distinguish the fly species. Results are important in that they present an effective strategy for apple maggot and are transferable to other cryptic pests.
2. Non-target effects of common orchard pesticides on a predatory mite. The non-target effects of pesticides on a common orchard predatory mite, Galendromus occidentalis, are well-described and used by orchardists to conserve this predator to prevent disruption of mite biological control. Another predatory mite, Amblydromella caudiglans, has also become common in apple orchards in recent years, but there is almost no research describing its pesticide sensitivity. Researchers at the USDA in Wapato, Washington in collaboration with scientists at Washington State University documented the non-target effects of common orchard insecticides and fungicides to Amblydromella. This information allows for modification of current recommendations to growers regarding which pesticides are least likely to disrupt mite biological control, which in turn will reduce the number of miticide applications they need to make each year.
3. Food supplements for improving biological control. Natural enemies may find it difficult to survive in orchards when pest populations are low and therefore cannot respond quickly to growing pest populations. Generalist natural enemies, some of which feed on non-pest resources (e.g. flower pollen, non-pest insects), may use these resources in times when other prey (pests) are scarce, which allows them to remain in the orchard even when pests are not present. Researchers at the USDA in Wapato, Washington, examined the ability of two predatory mites to reproduce and complete development on Typha pollen, brine shrimp cysts, and Ephestia kuehniella eggs, which are commercially available food supplement products. Neither predatory mite could consume Ephestia kuehniella eggs, but one species could complete development and reproduce on the pollen and cysts. Future work will examine the potential of these food products to boost populations of predatory mites in the field and to encourage grower-released natural enemies to remain in the orchard where they are released.
4. Rapid and repeatable host plant shifts drive reproductive isolation following a recent human-mediated introduction of the apple maggot fly. Apple maggot fly is a quarantine pest of apple in the western United States. Understanding the effects of host-shifting by flies as a mechanism for fly diversification is poorly understood. ARS researchers in Wapato, Washington, and Hilo, Hawaii, in collaboration with researchers at the University of Notre Dame, Wayne State University, Binghamton University, and Western Washington University, tested for genetic differentiation among apple maggot flies infesting apple and black and ornamental hawthorn fruit co-occurring at three sympatric sites. Evidence was found that populations of the three host-associations are genetically differentiated at the local level, indicating that partial reproductive isolation has evolved in the western United States. Results suggest that conditions suitable for initiating host-associated divergence may be common in nature, allowing for the rapid evolution of new host races when ecological opportunity arises.
5. Morphological and molecular genetic tools show that species diversity within the minute pirate bug complex of western North America is considerably larger than previously appreciated. Making full use of biological control opportunities in orchards requires tools for identifying predatory species of importance. Researchers at the USDA laboratory in Wapato, Washington, showed that the minute pirate bug (Orius) complex in western North America comprises at least ten native species instead of the four species commonly accepted in taxonomic treatments of this group, due to the discovery of previously unknown and undescribed species virtually identical in appearance to described species. Morphological, behavioral, and molecular genetic tools were employed in developing a dichotomous key to the ten species, allowing correct identification of species occupying agricultural and other habitats of western North America. Biological and geographic data collected during this research, when combined with these dichotomous keys, will allow fruit growers and pest control advisors to more effectively weigh the potential importance of these sources of biological control as they choose among different pest control options.
6. The artificial sweetener, erythritol, is insecticidal to pear psylla. Pear psylla is a key pest of commercial pear that requires repeated applications of insecticides to manage. New management tools are needed to reduce the risk that pear psylla populations will develop resistance to current insecticides. The artificial sweetener, erythritol, is non-toxic to humans but is insecticidal when ingested by certain insects. Researchers at the USDA laboratory in Wapato, Washington, and Heritage University in Toppenish, Washington, examined whether erythritol is also lethal to pear psylla. Results of laboratory and field experiments showed that treatment of pear with 20% erythritol causes 60-80% mortality of pear psylla nymphs and adults. These findings demonstrate that erythritol could be developed into a safe and effective tool for the management of pear psylla.
7. Methods for monitoring Trechnites, a key parasitoid of pear psylla. Pear psylla, the key insect pest of pear, is primarily controlled by pesticides while biological control by natural enemies remains underutilized. This is due in part to a poor understanding of the biology of its most important natural enemy, the parasitoid Trechnites spp. Researchers at the USDA in Wapato, Washington, in collaboration with scientists at Washington and Oregon State Universities, determined that screened sticky cards and custom-designed 3D-printed traps are effective methods for monitoring adult Trechnites and are superior to the traditional methods of monitoring by unscreened sticky card or beat tray. Additionally, the team determined that Trechnites parasitism levels can be monitored by molecular detection, visual observation following dissection, or using cardboard shelters to capture overwintering parasitized psylla. Future research will determine the relationship between adult Trechnites trap capture, psylla age distribution, and parasitism levels in the field so growers can anticipate the level of control provided by Trechnites in a given orchard.
8. Non-target effects of erythritol on the predatory mite Galendromus occidentalis. The artificial sweetener erythritol shows promise for controlling pear psylla. Pear psylla are currently the most critical pest of pears, but spider mites are ranked by growers as their second most important arthropod pest. Spider mite outbreaks occur when their natural enemies are killed by broad-spectrum pesticides used to control other pests, including pear psylla. To determine if erythritol can be integrated into pear pest management without causing spider mite outbreaks, researchers at the USDA in Wapato, Washington, examined the non-target effects of erythritol on the key predatory mite, Galendromus occidentalis in laboratory assays. Tests on this mite via multiple routes of exposure determined that erythritol is somewhat harmful to Galendromus occidentalis, but substantially less so than other psylla control products currently being used. Incorporation of erythritol into psylla management may allow growers to reduce the use of pesticides that are harmful to humans and beneficial organisms.
9. Determination of the thermal limits of apple maggot pupae. Apple maggot is a serious pest of apples in North America and is considered a pest of quarantine concern to most countries importing apples from the United States. Information on the survival and longevity of apple maggot under various rearing temperatures and day-lengths is needed to help predict the risk of apple maggot introductions in export countries. Researchers at the USDA in Wapato, Washington, investigated the potential impact of chill duration and exposure to tropical or subtropical climates and day-lengths on pupal diapause and subsequent adult emergence. They found that survival of apple maggot pupae was greatest when pupae were reared at 26-degrees C regardless of day-length, and that flies required more time to emerge when reared at lower temperatures and temperate day-lengths. These results will improve models to predict the probability of apple maggot to occupy environments different from those in North America.
10. Efficacies of cyantraniliprole, spinetoram, and Chromobacterium subtsugae biopesticide against Rhagoletis indifferens. Efficacies of cyantraniliprole, spinetoram, and Chromobacterium subtsugae biopesticide against western cherry fruit fly. Western cherry fruit fly is a quarantine pest of cherries in western North America. Diamides are a relatively new class of insecticides that appear effective in controlling fruit flies and could be useful in rotation with other insecticide chemistries to offset potential insecticide resistance. Personnel at the USDA laboratory in Wapato, Washington, compared efficacies of the diamide cyantraniliprole with that of the standard spinetoram and the biopesticide Chromobacterium subtsugae extract, either alone or mixed in bait against the fly. It was found that cyantraniliprole in bait caused as much or greater fly mortality and reduced oviposition more than spinetoram in bait. Chromobacterium subtsugae extract in bait usually did not cause mortality higher than controls. Results indicate that cyantranilirpole in bait could be useful as an insecticide for controlling western cherry fruit fly.
11. Distinct adult eclosion traits identified for sibling apple maggot fly and snowberry fly species. The apple maggot fly and snowberry fly are genetically closely related flies that attack apple and snowberry fruit, respectively. In part because of their use of different host plants, their responses to various environmental factors may have diverged. Personnel at the USDA laboratory in Wapato, Washington, Washington State University in Vancouver, Washington, and the University of Notre Dame, Indiana, compared the timing of adult fly emergence after their pupae were chilled or not. After chilling, emergence distributions of apple maggot flies were more dispersed than of snowberry flies. When pupae were not chilled, many more apple maggot than snowberry flies emerged. Results can benefit researchers who study evolutionary biology as well as Washington State Department of Agriculture and county pest control pest boards (regulatory agencies) that track emergence times and activity periods of apple maggot flies for management as well as activity periods of snowberry maggot flies, which can be confused with apple maggot flies.
Review Publications
Horwood, M., Milnes, J., Cooper, W.R. 2019. Brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae) (Stål, 1855), detections in Western Sydney, New South Wales, Australia. Austral Entomology. 58(4):857-865. https://doi.org/10.1111/aen.12421|.
Elmquist, D.C., Landolt, P.J., Cooper, W.R., Reed, H., Foutz, J., Clepper, T., Kacprzyk, B., Teig, D., Zack, R.S. 2020. Polistes venom compound N-3-methylbutyl acetamide is a sex pheromone of Polistes metricus Say and attracts males of several Polistes (Fuscopolistes) species. Journal of Economic Entomology. 113(12):10-73-1079. https://doi.org/10.1093/jee/toaa065.
Schmidt-Jeffris, R.A., Cutulle, M. 2019. Non-target impacts of herbicides on Tetranychus urticae and its predator, Phytoseiulus persimilis: implications for biological control. Pest Management Science. 75(12):3226-3234. https://doi.org/10.1002/ps.5443.
Wakie, T., Yee, W.L., Neven, L.G., Kumar, S. 2019. Modeling the abundance of two Rhagoletis fly (Diptera: Tephritidae) pests in Washington State, U.S.A.. PLoS One. 14(6). https://doi.org/10.1371/journal.pone.0217071.
Yee, W.L., Forbes, A.A., Feder, J.L. 2020. Eclosion and adult longevity traits of Rhagoletis tabellaria (Diptera: Tephritidae) and Utetes tabellariae (Hymenoptera: Braconidae) in the laboratory. The Canadian Entomologist. 152(2):145-158. https://doi.org/10.4039/tce.2019.74.
Doellman, M.M., Hood, G.R., Gersfeld, J., Driscoe, A., Xu, C., Sheehy, R., Holmes, N., Yee, W.L., Feder, J. 2020. Identifying diagnostic genetic markers for a cryptic invasive agricultural pest: a test case using the apple maggot fly, Rhagoletis pomonella (Diptera: Tephritidae). Annals of the Entomological Society of America. 113(4):246-256. https://doi.org/10.1093/aesa/saz069.
Yee, W.L., Goughnour, R.B. 2019. Assessments of Rhagoletis pomonella (Diptera: Tephritidae) infestation of temperate, tropical, and subtropical fruit in the field and laboratory in Washington State, U.S. Journal of British Columbia Entomological Society. 116(3):40-58.
Yee, W.L. 2020. Evaluation of Cyantraniliprole, Spinetoram, and Chromobacterium subtsugae extract in bait for killing and reducing oviposition of Rhagoletis indifferens (Diptera: Tephritidae). Journal of Economic Entomology. 113(3):1256-1362. https://doi.org/10.1093/jee/toaa056.
Yee, W.L. 2020. Laboratory evaluation of CX-10282 containing Beauveria bassiana (Hypocreales: Clavicipitaceae) strain GHA against adult Rhagoletis indifferens (Diptera: Tephritidae). Phytoparasitica. 48(2):231-245. https://doi.org/10.1007/s12600-020-00797-5.
Bergeron, P., Schmidt-Jeffris, R.A. 2020. Not all predators are equal: miticide non-target effects and differential selectivity. Pest Management Science. 76(6):2170-2179. https://doi.org/10.1002/ps.5754.
Neven, L.G., Wakie, T., Yee, W.L. 2020. Low temperature duration and adult rearing regimes affect eclosion of Rhagoletis indifferens (Tephritidae: Diptera). Environmental Entomology. 49(3):660-666. https://doi.org/10.1093/ee/nvaa044.
Wakie, T., Neven, L.G., Yee, W.L., Lu, Z. 2019. The establishment risk of Lycorma delicatula (Hemiptera: Fulgoridae) in the United States and globally. Journal of Economic Entomology. 113(1):306-314. https://doi.org/10.1093/jee/toz259.
