Location: Temperate Tree Fruit and Vegetable Research
2016 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 is the first report for this new project which began on October 26, 2015 and continues research from the previous project, “Biorational Management of Insect Pests of Temperate Tree Fruits”, 2092-22430-001-0D.
Substantial progress was made for all sub-objectives of Objective 1, to develop new knowledge of the biology of insect pests and their natural enemies.
Sub-objective 1A: Stink bugs were collected in 67 samples of natural and suburban vegetation to develop hypotheses on the habitats and types of plants used by a number of pest stink bugs, including brown marmorated stink bugs. In dry non-agricultural areas, plants that are succulents and plants with fruits accounted for most phytophagous stink bugs sampled. Brown marmorated stink bug distributions remained strictly urban.
Sub-objective 1B: Surveys were conducted to identify microbial species colonizing aphid honeydew in apple and pear orchards. Microbes associated with sentinel Petunia and Nicotiana flowers deployed in orchards and riparian areas were also surveyed. A total of 40 bacterial species from 16 genera were identified by sequencing 16S rDNA. Volatiles produced by these microbes were tested for their attractiveness to assorted insect group in field trapping trials. These trapping trials showed that small Drosophila, Noctuid moths, beneficial parasitoids in the Ichneumonidae, and Vespid wasps were attracted to microbe-associated volatiles.
Sub-objective 1C: Experiments on Western cherry fruit fly were conducted to determine the effects of moist vs. dry soil and bare ground vs. grass cover on pupal mortality and adult emergence. Preliminary studies indicated that unlike some other fruit flies, pupal Western cherry fruit flies are tolerant of dry soil and dry grass and are well adapted to climates with little moisture during the summer. Flies emerged significantly earlier from bare soil than from grass, but total emergence was not consistently different. Results may help explain the current distribution of Western cherry fruit fly, and may be useful for predicting their potential establishment in other regions of the world.
Sub-objective 1D: The upper and lower thermal limits of Western cherry fruit fly adults and pupae were determined by measuring oxygen consumptions and metabolic rates of insects under a range of temperatures. Results indicated that as adult flies age, their range of thermal tolerance decreases. Also, overwintering pupae remain resistant to freezing until just before they emerge as adult flies.
Sub-objective 1E: A genome editing system to study protein function was developed for codling moth. Experiments to optimize the amount of genome editing were performed. Preliminary studies indicated that we have developed a functional CRISPR/Cas9 technique for use in codling moth that creates gene mutations with high efficiency. This gene editing tool will allow researchers to characterize the proteins involved in the molecular mechanisms of codling moth host or mate finding behaviors.
Sub-objective 1F: Over 1,000 specimens of minute pirate bugs have been obtained during our own collecting efforts and as loans to us from University and USDA entomology museums. The specimens are in the process of being sorted and carefully examined, with final objectives being to produce a new key to the minute pirate bugs of North America. Traits under examination include color, external morphology, and size and form of the male and female genitalia. On-loan specimens are being re-labeled with correct identifications in the event that the loaned specimen was misidentified.
Progress was also made in subordinate projects highly related to Objective 1: A set of compounds in wine and produced by yeasts were tested as attractants for Polistes paper wasps, as part of an effort to mitigate problems with these wasps at Air Force Bases. Although the work is ongoing, results are promising with a 250% improvement in the catch of these wasps in traps compared to current technology. Additionally, a second set of these yeast-produced compounds was found to be attractive to yellowjacket wasps.
In another subordinate project, pear psylla were collected from Washington and Oregon to survey populations for associated bacterial endosymbionts. Two bacteria - Arsenophonus and Phytoplasma pyri - were present in a large number of insects. Results of laboratory experiments suggest that Phytoplasma decreases fecundity and mobility of psylla. Future experiments will investigate the effects of Arsenophonus on psylla biology.
Progress was made for both sub-objectives of Objective 2, to develop alternatives to fumigation to meet quarantine restrictions for pest insects in exported fruits.
Sub-objective 2A: Preliminary assessment has been made of volatile compounds emitted by mature apple. This information will provide a basis for comparison with fruit infested by codling moth to identify biochemical markers for infested apples.
Sub-objective 2B: Studies have been initiated to improve ecological niche models for codling moth and Western cherry fruit fly to better estimate establishment and spread of these pests in export markets. To support these models, extensive field surveys for codling moth and Western cherry fruit fly were completed, and synthesis of available data on the public database, Pestworld, has been completed.
Progress was made for most sub-objectives of Objective 3, to develop and improve methods to reduce pesticide use and to develop alternatives to pesticides.
Sub-objective 3A: Field tests have confirmed control of codling moth in apple orchards with kairomone-baited traps at 50 traps per acre. Thirty-day tests of trapping out codling moths in 4 acre plots showed 70+% reductions in new damage to the crop over this time frame. Laboratory studies of release rates of these kairomone compounds provided a sachet dispenser system to replace the more expensive vial system. The new sachet dispenser was validated as equally attractive when tested as a lure in traps in field trials. Initial moth retention and influence of field-aging was compared among different adhesive trap liners used in mass-trapping approaches for codling moth and leafrollers. Results indicate that different trap liners vary in mass-trapping efficacy. A non-saturating bucket trap filled with certified-organic mineral oil or propylene glycol for non-organic orchards caught ten-times more moths and required less labor than the standard sticky trap with removable liners.
Sub-objective 3B: Studies have been initiated to attract and retain natural enemies in orchards using plant derived volatiles and supplemental foods sources.
Sub-objective 3C: A first set of experiments testing the effects of three temperatures on kill and oviposition of flies exposed to the insecticides spinosad (Entrust) and spinetoram (Delegate) was completed.
Accomplishments
1. Development of an inexpensive kairomone dispenser system for use in codling moth mass trapping. Codling moth is a key pest of apple, pear, and walnuts in the United States and elsewhere in the world. New approaches and technologies, such as mass trapping with lures for female moths, are needed to replace pesticide applications and to augment mating disruption which is in widespread use. ARS scientists in Wapato, Washington, developed an inexpensive sachet system for providing optimized controlled release of acetic acid, a fruit volatile, and pear ester as a lure for female and male codling moths. Field tests validated the attractiveness and performance of the new dispenser system as a lure for traps. Previous and parallel research demonstrated control of codling moth damage at 50 kairomone-baited traps per acre, and reduced costs for lures and traps will benefit growers adopting this approach. These developments show promise as new technologies for the control of codling moth by conventional and organic fruit growers.
2. Identification of ammonium carbonate loss rates that maximize catches of Western cherry fruit fly while minimizing non-target insect captures. Western cherry fruit fly is a quarantine pest of sweet cherry in the Pacific Northwest of the U.S. that can be monitored using traps baited with ammonia. However, ammonia-based attractants also attract non-target flies that clutter traps and reduce trap efficiency. ARS researchers in Wapato, Washington, determined whether ammonium carbonate (AC) loss rates from lures differentially affect numbers of cherry fruit fly and non-target flies caught on sticky yellow traps in cherry trees. Results showed that lures with an AC loss rate of 0.19 mg/hour maintained high cherry fruit fly captures while reducing non-target fly captures. This rate thus should be used for monitoring cherry fruit flies in areas where there are many non-target flies.
3. Effectiveness of benzoid plant volatiles plus acetic acid to monitor Obliquebanded leafroller in apple orchards under mating disruption. Effective, low-cost monitoring of tree fruit pests is an important component of developing integrated programs which can minimize the use of insecticides. ARS researchers in Wapato, Washington, in collaboration with researchers in Chile and Canada developed a new lure for obliquebanded leafroller and compared it with a sex pheromone lure in orchards treated with sex pheromone. It was determined that the new lure was more effective than the sex pheromone lure and caught both sexes. Information from this research supports the continued effort to develop even more effective lures that can be used in trap-based monitoring program for important moth pests in tree fruits.
4. Mapping global potential risk of establishment of Rhagoletis pomonella (Diptera:Tephritidae) using MaxEnt and CLIMEX niche models. The apple maggot is a major quarantine pest of apples in the U.S. To reduce the threat of apple maggot to export countries and to facilitate the movement of commercial apples, an assessment of potential risk of establishment of apple maggot in export countries is needed. ARS researchers in Wapato, Washington, and Colorado State University in Fort Collins, Colorado, used the predictive models MaxEnt and CLIMEX to determine global potential risk of establishment of apple maggot. Both models correctly predicted the known distribution of apple maggot in North America and mostly agreed on climatic suitability worldwide for the fly. Our results are important because they can be used to make science-based international trade decisions on apple movement by policy makers.
5. Taxonomic reassessment of the minute bug fauna of the western United States. The minute pirate bugs (Orius) are important sources of biological control in agricultural crops worldwide. ARS scientists in Wapato, Washington, found that the minute pirate bug fauna in western North America includes specimens whose body traits differ from traits of described species, suggesting that the minute pirate bugs of North America are actually a complex of described species and undescribed cryptic species. Body traits allowing identification of undescribed species were defined, and separation of species using these characteristics was confirmed by an analysis of DNA-sequences. These results will help scientists, field biologists, and others interested in biological control to identify minute pirate bugs found in agricultural crops of western North America, leading to more efficient use of these species in biological control. Results additionally raised concerns about whether identifications of minute pirate bugs in the North American biological control literature may often be incorrect.
6. Reduction of optimal thermal range in aging western cherry fruit flies. The western cherry fruit fly is an economically important pest of sweet cherries in the western U.S., and may have potential to spread to new areas. This potential to invade other geographic areas is probably limited by intolerance to extreme temperatures resulting in a shutdown of metabolic activity and development. This can be measured as its oxygen consumption and metabolic rate. ARS scientists in Wapato, Washington, determined that the fly tolerance of temperature extremes is impacted by the age of the fly. Newly emerged flies showed the broadest tolerance to temperatures, maintaining metabolic activity from 6.6 to 42.2 degrees Celsius (a range of 35.8 degrees), and fly tolerance to temperature variation was reduced with age; 28-day old flies showed the shortest range of temperatures suitable for metabolic activity from 10.5 to 37.8 degrees Celsius (a range of 27.2 degrees). These results were used to refine a model to predict the potential distributions of this pest on national and global bases, which in turn is being used by the northwest sweet cherry industry to renegotiate current and establish new trade agreements where quarantine restrictions exist against the western cherry fruit fly and the models show no risk of invasion.
7. How far south can codling moth spread in China? Potential distribution and stages of invasion are critical information. Codling moth, Cydia pomonella, is a major quarantine pest of apples in the U.S and several other countries. Although codling moth originally developed in central Asia Minor, most likely Kazakhstan, it was not reported in China until 1953. ARS scientists in Wapato, Washington, and scientists at Colorado State University in Fort Collins, Colorado and the Institute of Zoology, Chinese Academy of Sciences in Beijing, China, collaborated to model the stages of invasion of this pest in China as well as identifying those areas most at risk of invasion by this pest. The model accurately predicted the progression of codling moth using 2010 data and comparing to 2015 currently infested areas. The revised model showed those regions most at risk of invasion by this pest and showed areas of invasion stages of population stabilization, colonization, adaptation, and sink. These data will be used to develop improved, environmentally sustainable monitoring and management practices in China, which will help to stem the spread of this pest on a global level as exports of Chinese apples increase.
8. Improved trapping of pestiferous paper wasps on Air Force Bases. Several species of Polistes wasps cause problems at Air Force Bases in the Southeast U.S., both as a stinging hazard at base housing, but more importantly within Air Traffic Control towers where they form mating and overwintering swarms in autumn. ARS scientists in Wapato, Washington, Gainesville, Florida, and Poplarville, Mississippi, working with scientists at Sterling International Inc. of Spokane, Washington, and the Tyndall and Moody Air Force Bases in Florida and Georgia respectively, developed a new combination lure-and trapping system that is far more effective than previous systems tested, and discovered a yeast-produced chemical that improves the catch of these wasps on traps by 250%. Testing of chemicals as attractants continues, but these results provide improved means to manage wasp populations in limited areas where they are pestiferous.
9. Identification of bacterial endosymbionts associated with pear psylla. Pear psylla is a key pest of pear in the western United States. Psyllids are often associated with bacterial endosymbionts that can alter the insects' susceptibility to parasitism, insect pathogens, and insecticides. ARS scientists in Wapato, Washington, screened pear psylla populations in the Pacific Northwest for bacterial endosymbionts. They found that all populations carry the endosymbiont Arsenophonus, which provides another psyllid pest with protection against parasitism. They also found that Phytoplasma pyri, a pathogen associated with pear decline disease and yellow peach leafroll disease, was more prevalent in psylla populations in the Yakima Valley than in other regions. This study is the first to characterize the diversity of endosymbionts of pear psylla in North America.
ARS scientists in Wapato, Washington, mentored research projects by two undergraduate students for the Research for Undergraduates (REU) program at Heritage University, a predominantly Hispanic-serving liberal arts college located on the Yakama Indian Reservation. The projects consisted of 1) isolating and characterizing the salivary proteins of pear psylla, and 2) assessing the effects of Phytoplasma infection on pear psylla behavior.
Review Publications
Galdino, T., Kumar, S., Oliveira, L., Alfenas, A., Neven, L.G., Al-Sadi, A., Picanco, M. 2016. Mapping global potential risk of mango sudden decline disease caused by fungus Ceratocystis fimbriata. PLoS One. 11(7):e0159450.
Cooper, W.R., Horton, D.R. 2015. Effects of elicitors of host plant defenses on pear psylla (Cacopsylla pyricola: Psyllidae). Entomologia Experimentalis et Applicata. 157:300-306.
Walker, W.B., Gonzalez, F., Garczynski, S.F., Witzgall, P. 2016. The chemosensory receptors of codling moth Cydia pomonella – expression in larvae and adults. Scientific Reports. doi: 10.1038/srep23518.
Neven, L.G., Hale, A. 2015. Use of scanning calorimetry and microrespiration to determine effects of Bt toxin doses on Pandemis leafroller (Lepidoptera: Tortricidae) metabolism. Trends in Entomology. 11:39-46.
Yee, W.L., Alston, D.G. 2016. Sucrose mixed with spinosad enhances kill and reduces oviposition of Rhagoletis indifferens (Diptera: Tephritidae) under low-food conditions. Journal of Entomological Science. 51(2):101-112.
Yee, W.L., Klaus, M. 2015. Implications of Rhagoletis zephyria, 1894 (Diptera: Tephritidae), captures for apple maggot surveys and fly ecology in Washington state, U.S.A. Pan-Pacific Entomologist. 91(4):305-317.
Horton, D.R., Lewis, T.M., Garczynski, S.F., Thomsen Archer, K.L., Unruh, T.R. 2016. Morphological and genetic reappraisal of the Orius fauna of the western United States (Hemiptera: Heteroptera: Anthocoridae). Annals of the Entomological Society of America. doi: 10.1093/aesa/sav155.
Wang, J., Gu, L., Ireland, S., Garczynski, S.F., Knipple, D.C. 2015. Phenotypic screen for RNAi effects in the codling moth Cydia pomonella. Gene. 572:184-190.
