Location: Commodity Protection and Quality Research
2020 Annual Report
Objectives
Objective 1: Develop practical, systems-based strategies, for management of pests of fresh fruit and high valuable durable commodities (e.g., navel orangeworm in almonds, pistachios and walnuts, mealybugs on table grapes, codling moth in walnuts, tephritid fruit flies in fruit) through all aspects of production, distribution, and marketing that enhance production and commodity quality.
Subobjective 1A: Characterize the biotic and abiotic factors that affect the insecticides used to control navel orangeworm in tree nuts in order to optimize their efficacy and minimize non-target impacts on human health and environmental quality.
Subobjective 1B: Characterize and optimize semiochemical strategies for monitoring and control of key dipteran and lepidopteran pests in the context of minimizing preharvest and post-harvest chemical treatment requirements.
Subobjective 1C: Characterize and optimize control strategies, utilizing the physiology of key lepidopteran, coleopteran and dipteran pests, in the context of minimizing preharvest and post-harvest chemical treatment requirements.
Subobjective 1D: Develop an overall metric of treatment efficacy, via combining the individual contributions from preharvest and post-harvest processes, to evaluate systems-based strategies for insect control in fresh and durable commodities.
Objective 2: Develop new treatment technologies or modify existing protocols for post-harvest treatment of pests, such as the Indianmeal moth and the red flour beetle, with the objective of minimizing negative effects to the environment and food quality, while maintaining the positive sensory qualities and marketability of these commodities.
Subobjective 2A: Develop technologies to reduce, or eliminate, atmospheric emissions from ventilation effluent following post-harvest fumigations.
Subobjective 2B: Develop treatments for novel post-harvest applications involving fresh and durable commodities.
Subobjective 2C: Improve semiochemical-based strategies for controlling stored product insect pests in post-harvest scenarios.
Objective 3: Develop treatment technologies for action agencies that require alternatives to methyl bromide for phytosanitary and quarantine treatment of pests such as the codling moth, spotted wing drosophila, and Fuller rose beetle. Conduct research to support USDA-APHIS negotiations with trade partners as well as research on the fate and transport of post-harvest agrochemicals, thereby enhancing the competitiveness of U.S. agriculture in the global marketplace.
Subobjective 3A: Develop post-harvest treatments for quarantine purposes that minimize reliance on post-harvest methyl bromide (MeBr) fumigations.
Subobjective 3B: Obtain sorption and depuration data related to post-harvest fumigations to serve as physicochemical basis for regulation related to nontarget human ingestion and inhalation exposures.
Subobjective 3C: Identify agrochemical use strategies and novel technologies to ensure foodstuff residues are compliant with importer regulations.
Approach
The first objective has four subobjectives focusing on navel orangeworm, fruit fly, Indianmeal moth, and assorted pests through production, packing and shipping as well as damage prediction. These goals will be attained using a collaborative and multidisciplinary research approach combining chemical analysis, insect physiology, population dynamics, damage prediction and assessment of natural enemies. These elements will then be integrated into a systems approach that can be applied from the field through all channels in production and export.
The second objective, which has three subobjectives, is focused on the development of new technologies and/or modifications of existing protocols for post-harvest treatment of insects such as Indianmeal moth and red flour beetle. Particular emphasis will be placed on reducing fumigant emission into the atmosphere and the development of new fumigation protocols that retain commodity quality. Strategies employing semiochemicals instead of fumigants will be investigated for control of Indianmeal moth in warehouses.
The final objective has three subobjectives and is focused on control of quarantine pests in recently harvested commodity in storage. Sorption and depuration data will be obtained to help quantify nontarget human exposure in order to improve worker safety. These strategies ensure that foodstuff residues are compliant with importer regulations.
Progress Report
This is the final report for project 2034-43000-040-00D, which terminated in July 2020 and continues under bridging project 2034-43000-042-00D. Substantial results were realized over the five years of the project. Progress was made on all objectives and their sub-objectives, which fall under two components of National Program 304. Under Component 3, Insects and Mites, research focused on Problem Statements 3A1: Early detection and prevention of emerging crop pests and on Problem Statement 3A2: Systems approach to environmentally sound pest management. Under Component 4, Protection of Post-harvest Commodities, Quarantine, and Methyl Bromide Alternatives, research addressed Problem Statement 4A: Arthropod pests of fresh commodities and Problem Statement 4B: Arthropod pests of durable commodities.
Under Sub-objective 1A, field studies were conducted that quantified the duration of control of insecticides (three families) used to control navel orangeworm (NOW), the primary lepidopteran pest of almonds and pistachios in California. These studies evaluated egg, larval, and adult toxicity, as well as the role played by additives (adjuvants) that enhance spreading and provide protection from ultraviolet radiation. Research conducted in Parlier, California, demonstrated that while the new selective insecticides protected nuts for as long as 28 days, they needed to be applied earlier in nut development than the older chemistries that are currently being phased out. These studies provided new strategies to enhance current control schemes by improved timing. Additional research assessed methods to mitigate insecticide drift. Collaborative studies with researchers at the University of Illinois, Urbana, Illinois, elucidated the mechanism of pyrethroid insecticide resistance, assessed the potential of pyrethroid resistant moths to develop resistance to other families of insecticide, and established that NOW and the fungus that produces aflatoxin B1, Aspergillus flavus, have a mutualistic relationship. Navel orangeworm adults and larvae transport the fungus and larval survival is greater in nuts infested with A. flavus. Related research conducted in support of Sub-objective 1D laid the groundwork to identify high risk almond and pistachio orchards so that additional insecticide sprays could be applied before damage occurred. Research on improving insecticide timing conducted for Sub-objective 1A led to the development of temperature based (Degree Day) protocols for monitoring almonds and pistachios. The pistachio industry now uses these timing protocols for control. A damage database was created for pistachios for the years 2007-2017 and the information will be evaluated in the coming years. The goal of identifying high risk orchards remains elusive because the wide-spread adoption of mating disruption in almonds and pistachios has reduced the efficacy of pheromone lures. This issue is addressed by the research conducted in support of Sub-objective 1B.
Mating disruption for NOW has been available since 2008. Under Sub-objective 1B, research was conducted to increase the efficacy of mating disruption and develop monitoring tools for orchards using this technology. Further characterization of the mechanism of mating disruption for NOW revealed that the initial interaction of males with pheromone is important. The research on the importance of the timing of pheromone emission and lure spacing enabled manufacturers to improve their products. These data also helped improve mating disruption for control of stored product lepidopteran pests, such as the Indian meal moth. Unfortunately, mating disruption greatly reduces the utility of pheromone monitoring lures for fields using this technology as well as nearby fields (mating disruption can affect traps at distances >1 mile from the emitter). Research compared the attractancy of a lure containing a blend of five volatile chemicals identified from almonds and a previously described compound, phenyl propionate. The traps using phenyl propionate, both in orchards undergoing mating disruption and orchards that were not, consistently captured more moths than the lure containing the five volatile chemicals. The effectiveness of phenyl propionate could be significantly improved by placing a pheromone lure in the same trap. Trap design also influenced moth capture. Cutting openings in the sides of the most commonly used delta traps increased male capture, and delta traps with both open sides and a pheromone lure were even better. Wing traps (a more open design) containing only phenyl propionate were more effective than the modified delta traps.
Under Sub-objective 1C, research focused on developing new lures and technologies to monitor Tephritid fruit flies, which cause damage to fresh fruit across the world. The damage caused is estimated in the billions of dollars annually. New attractants were developed for key Tephritid fruit fly pests, including the Mexican Fruit Fly, and Mexican Fruit Fly traps baited with the attractants are currently undergoing field testing across the globe, providing critical programmatic support to USDA Animal and Plant Health Inspection Service (APHIS), Food and Agriculture Organization, International Atomic Energy Agency, and California Department of Food and Agriculture (CDFA).
Under Sub-objective 2A, a series of studies evaluated the ability of activated carbon (AC) sorbents from walnut and almond shells as well as peach and prune pits to sorb (adsorb or absorb) methyl bromide from ventilation effluent following postharvest fumigations. AC sorbents from prune pits had the highest capacity. Additional experiments demonstrated that electrolysis successfully broke down >80% of methyl bromide very efficiently.
Under Sub-objectives 2B and 2C, research supported market retention and/or expansion and served as the basis for technical interaction between industry, USDA-Foreign Agricultural Service (FAS), USDA-APHIS, Environmental Protection Agency (EPA), and respective counterparts in foreign governments. Postharvest measures were developed to control Asian Citrus Psyllid using ethyl formate fumigation of trailer loads in the grove. This research served as the basis for CDFA policy. Brown Marmorated Stinkbug was controlled with ethyl formate fumigation and sulfuryl fluoride fumigation, in order to retain market access for U.S. automobiles to Australia and New Zealand, ($20 billion annually). Spotted wing drosophila and black widow spiders were controlled with ozone fumigation in table grape exports to Australia ($180 million annually). Bean thrips were controlled with postharvest phosphine fumigation to retain market access for fresh citrus to Australia ($20 million annually). Postharvest methyl bromide fumigation was used to control codling moth infesting inshell walnuts packed in new fiberboard cartons to support continued export to Japan ($80 million annually).
Under Sub-objective 3A, the tolerance of mandarins, navel and Valencia oranges, lemons and grapefruit to phosphine fumigation was assessed because a fumigation treatment is useless if it injures the commodity when applied. Methyl bromide fumigation and cold treatment, two treatments that have been used in the past for citrus quarantine, were also evaluated for comparison, as well as a combined phosphine application followed by methyl bromide fumigation after storage. Visual and internal quality, including sensory impact, was determined for each treatment. Results indicated that phosphine did not harm citrus quality including taste, but methyl bromide was often quite injurious, particularly with lemons and grapefruit. Novel methyl bromide chamber fumigations were developed for postharvest control of spotted wing drosophila in fresh sweet cherry exports from the Western United States ($100 million annually) as well as codling moth in Japanese plum exports to Japan ($10 million annually) under Sub-objective 3 A. A kinetic model of sorption was developed based on the measurement of methyl bromide and how calculated exposures varied across the fumigation trials.
Under Sub-objectives 3B and 3C, researchers developed new methods to quantify agrochemical residues in order to overcome specialty crop trade barriers and in support of determining maximum residue levels (MRLs). These methods were used to quantify residues of propylene oxide and its halohydrins, which ensured the market access of California almonds and walnuts to the European Union (EU), valued at $2.5 billion annually. The transfer of this method to EU chemists and regulators directly resulted in the establishment of a temporary phosphorous acid MRL for tree nuts, thereby preserving the export of California tree nuts until a permanent import tolerance was established in January 2019. Fumigations were optimized from the perspective of efficacy as well as human and environmental health, and exposure data were submitted to support a Section 3 postharvest registration of ethyl formate, enabling its use to control Asian citrus psyllid. Additional data on worker and consumer exposure to sulfur dioxide was used to treat table grape and blueberry exports ($500 million annually) and for sulfur dioxide-releasing sodium metabisulfite products used to treat table grape exports and imports ($800 million annually) and for blueberry exports ($15 million annually). The ultimate goal of this research is to provide a framework to optimize quarantine fumigation schedules for insect control. This will promote more strategic technical and economic Quarantine Pre-shipment (QPS) use of methyl bromide as well as minimize the exposure of workers. These data also support the efforts of other U.S. action agencies, including FAS and EPA, to maintain current agricultural markets as well as increase U.S. market share worldwide.
Accomplishments
1. New methods to control invasive horticultural pests and pests of quarantine importance. ARS scientists in Parlier, California, developed a postharvest methyl bromide fumigation protocol for control of codling moth infesting inshell walnuts packed in new fiberboard cartons to support continued export to Japan, valued at $80 million annually. A quarantine protocol for trailers of citrus using postharvest fogging was developed for Asian citrus psyllid. A postharvest phosphine fumigation was developed for bean thrips to retain market access for fresh citrus to New Zealand, valued at $20 million annually. Postharvest phosphine fumigation protocols were developed for control of black widow spider and spotted wing drosophila to retain market access for table grapes to Australia valued at of $180 million annually. The research conducted directly resulted in market retention or expansion and served as the basis for technical interaction between industry, USDA- Foreign Agricultural Service, USDA-Animal and Plant Health Inspection Service, and respective counterparts in foreign governments.
2. Optimizing fumigations for increased efficacy and human and environmental health. Data on worker and consumer exposure to fumigants are essential to ensure continued use of these chemicals and maintain and/or expand U.S. market share. Data were submitted to support a Section 3 postharvest registration of ethyl formate, to allow its use to control Asian citrus psyllid in the grove to limit the spread from quarantines. Worker and consumer exposure data were submitted to support a Section 3 reregistration of sulfur dioxide used to treat table grape and blueberry exports valued at $500 million annually. Worker and consumer exposure data were submitted to support a Section 3 reregistration of sulfur dioxide-releasing sodium metabisulfite products used to treat table grape exports and imports valued at $800 million annually. Worker and consumer exposure data were submitted to support a Section 18 and 24c registration of sulfur dioxide-releasing sodium metabisulfite products used to treat blueberry exports valued at $15 million annually. The ARS research conducted in Parlier, California, directly resulted in registration of these products and served as the basis for technical interaction between industry, U.S. Environmental Protection Agency, and respective counterparts in state governments.
3. Fumigation with phosphine is safe for citrus quarantine. An alternative to methyl bromide fumigation is needed because the use of this quarantine fumigant is being phased out and its use is not desired by some U.S. trading partners. ARS researchers in Parlier, California, tested the tolerance of mandarins, navel and Valencia oranges, lemons and grapefruit to phosphine fumigation and determined that no measure of quality, including taste, was adversely affected by phosphine. This contrasted with methyl bromide, which was found to often damage the exterior of the fruit and sometimes reduce flavor quality. This research gives support for the usage of phosphine as a quarantine fumigant to replace methyl bromide.
4. Flight mill and wind tunnel studies identify importance of factors in field performance of mass-released sterile navel orangeworm. A pilot project is examining the possibility of using the mass rearing and sterilization facility in Phoenix, Arizona, to support an area-wide program for control of the navel orangeworm (NOW) in California tree nut crops. Initial research found that NOW females sterilized and shipped from the Phoenix facility competitively attracted and mated with wild males, but that released sterile males did not come to pheromone lures or calling females as efficiently as expected. Flight mill and wind tunnel studies conducted by researchers in Parlier, California, in collaboration with the University of California, Riverside, found no significant difference in the performance of irradiated and unirradiated Phoenix strain males shipped from the mass rearing facility. The flight mill study revealed that when the Phoenix mass rearing strain males were reared locally, they flew longer and farther than Phoenix strain males sent from the mass rearing facility, and similar trends were evident with respect to pheromone source contact in the wind tunnel study. Females performed better than males on the flight mill, and in their case, irradiation seemed more important than strain effects. These data suggest that factors involved with the production, sterilization, and shipping of navel orangeworm males are more important than irradiation or strain in predicting performance in the field.
5. Evaluating techniques to reduce insecticide drift. Insecticide drift can occur when the outer row of an orchard is sprayed, and this becomes a concern when orchards are located near waterways and other sensitive habitat. Over the course of two years, researchers in Parlier, California, in collaboration with researchers at the University of California, Berkeley, California, the Coalition for Urban Rural Environmental Stewardship, Davis, California, and California Department of Food and Agriculture, Sacramento, California, documented the extent of drift in three nut crops and evaluated two techniques to mitigate drift. One technique utilized opposing sprayers moving in synchrony and the second technique blocked the air intake on one side of the spray rig. Blocking the air intake was superior and did not compromise coverage compared to the grower standard. Adoption of this modification by growers will reduce drift and mitigate the environmental impact of insecticide use in California. Information was also collected on insecticide distribution within the orchard canopy, which in turn will be used to increase application efficacy in future studies.
6. Monitoring and documenting dispersal of navel orangeworm between walnut and almond. The navel orangeworm (NOW) is the most important insect pest of almonds, and an important pest in walnuts. To determine if walnut infestation was due to resident populations or NOW developing in adjacent almonds immigrating into walnut orchards later in the season, ARS researchers in Parlier, California, along with researchers at the University of California Division of Agriculture and Natural Resources, used fatty acid profile analysis to determine the larval host of trapped adults. When the crops were adjacent, almond was a net source and walnut was a net sink. Examination of sex difference found that the proportion of males trapped in pheromone traps in walnut orchard that originated in almond orchards was greater than the proportion of gravid female immigrants found in oviposition bait traps. Moreover, the proportion of females trapped in walnuts that developed on almond increased during the critical August walnut husksplit period, when walnuts became more susceptible to NOW. These results demonstrate dispersal of NOW from almond to walnut. Additionally, the lower number of female vs male immigrants found in walnuts when ovipositional bait was compared to pheromone lures is consistent with the premise that the ovipositional bait traps have a smaller radius of attraction than pheromone lures. This in turn suggests that these traps might help identify situations in which walnut husksplit treatments are needed for protection against immigrating NOW.
7. Evaluating the use of insecticide to augment sanitation in almond orchards. The navel orangeworm (NOW), the primary insect pest of almonds in California, is controlled in part by winter sanitation. Mummies, nuts left over left over in trees after harvesting, are removed from the tree and then shredded, but heavy rains in January through early February can prevent the shakers from entering the orchard, and hundreds of nuts may remain on the tree. ARS researchers in Parlier, California, combined research on the duration of insecticide control with NOW phenology to identify the critical time when mummy nuts serve as resource for NOW (typically April 24-May 10). An industry-wide effort in the San Joaquin Valley applied selective insecticide sprays to the mummies in 2018 and 2019 and overall damage was evaluated. There was a dramatic reduction in NOW damage and the almond growers in the Sacramento Valley are now utilizing this strategy as well to reduce insect damage and maintain almond quality.
8. Identification of the salivary effector genes in brown marmorated stink bug. The brown marmorated stink bug (BMSB), an invasive insect prevalent in 46 U.S. states and four Canadian provinces, has caused severe agricultural losses across several crops and is particularly damaging to orchard crops, such as apples and grapes. A team led by ARS researchers and involving scientists from several institutions spanning eight countries, performed the BMSB’s genome assembly and analysis. This work identified a wide variety of gene families and genetic elements responsible for the peculiar traits of this important pest. An ARS researcher in Parlier, California, worked to identify and annotate 64 genes encoding salivary effector proteins in the BMSB genome. Salivary effector proteins are secreted as part of insect saliva to suppress plant defenses as well as to perform extra-oral digestion. The discovery of salivary effector genes in the BMSB genome is significant because these genes likely aided the rapid spread and successful establishment of BMSB across North America through generalist herbivory and have potential future use in development of biomolecular pesticide applications.
Review Publications
Burks, C.S., Higbee, B.S., Beck, J.J. 2020. Traps and attractants for monitoring navel orangeworm (Lepidoptera: Pyralidae) in the presence of mating disruption. Journal of Economic Entomology. 113(3):1270-1278. https://doi.org/10.1093/jee/toz363.
Burks, C.S., Thomson, D.R. 2020. Factors affecting disruption of navel orangeworm (Lepidoptera: Pyralidae) using aerosol dispensers. Journal of Economic Entomology. 113(3):1290-1298. https://doi.org/10.1093/jee/toaa010.
Abrams, A.E., Kawagoe, J.C., Walse, S.S. 2020. Sulfuryl fluoride fumigation to control brown marmorated stinkbug (Hempitera: Pentatomidae). Postharvest Biology and Technology. 163. https://doi.org/10.1016/j.postharvbio.2019.111111.
Haack, S.E., Walse, S.S., Nguyen, K., Adaskaveg, J.E. 2019. Management of Xanthomonas fragariae with pre- and postharvest treatments to overcome trade barriers for California strawberries. Plant Disease. 103(6):1256-1263. https://doi.org/10.1094/PDIS-08-18-1395-RE.
