Research Project: Systems-Based Approaches for Control of Arthropod Pests Important to Agricultural Production, Trade and Quarantine

Location: Commodity Protection and Quality Research

2021 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 the bridging project 2034-43000-042-00D, “Systems-based Approaches for Control of Arthropod Pests Important to Agricultural Production, Trade and Quarantine,” which began on 07/13/2020 and was replaced on 12/07/2020 by project 2034-43000-043-00D, “Improved Systems-based Approaches that Maintain Commodity Quality and Control of Arthropod Pests Important to U.S. Agricultural Production, Trade and Quarantine.” In support of Sub-objective 1A, flight cylinder assays were used to examine the impact of cold exposure on navel orangeworm reared at Parlier, California, to support the Sterile Insect Mass Rearing Program for this insect. Adults exposed to 4°C for 24 hours did not perform significantly worse on this test, and three days at this temperature were required for a significant reduction in the number of males leaving the flight cylinder. A separate flight tunnel test found a small but significant reduction in performance in males shipped overnight in cold compared to those held in a cold room over the same time. These results suggest that the effect of cold might be cumulative over the time of transport rather than an acute response to the cold collection system in the mass rearing facility, and that transport stress in addition to cold might contribute to loss of vigor. This information will help improve the competitiveness of mass reared sterile males. In further support of Sub-objective 1A, a series of field trials were conducted to determine if the water volume used for insecticide application in pistachios could be reduced from 100 gallons per acre to 50 gallons per acre using organosilicone adjuvants. These trials began in June 2020 and are split over the life of this bridging program and succeeding program. Initial trials indicated that although lower concentrations of organosilicone adjuvant (0.03%) were sufficient for three weeks of control using 100 gallons water per acre, they did not work at 50 gallons per acre. Subsequent trials were conducted after July 13 and are reported in the succeeding program report. In support of Sub-objective 1B, a long-term study of pistachio risk factors for high navel orangeworm infestation, field data on degree day accumulation and harvest assessment were collected and added to an existing database. This study was negatively impacted by COVID-19 because face to face meetings were suspended, which delayed the project start, and insect damage was unusually low in pistachios for the years 2019 and 2020. In support of Sub-objective 1C, research was conducted to increase the efficacy of lures used to trap field populations of insect pests of fresh fruit. ARS researchers in Parlier, California, previously developed a methodology to quantify emission of pheromones from polymer disks into an airstream as a function of abiotic environmental parameters. The kinetic approach yields laboratory predictions of the potential for environmental loss prior to conducting field bioassays, ensuring the attractant lasts for the duration of the evaluation. Results were transferred to: USDA Animal Plant Health Inspection Service; FAO International Atomic Energy Agency; California Department of Food and Agriculture, and Florida Department of Agriculture. In support of Sub-objective 1D, research was conducted to generate the molecular resources for California red scale (CRS), a major pest of citrus plants. Initially, a laboratory colony of CRS was established on rough lemon plants under controlled environmental conditions at Parlier, California. Both male and female CRS samples were collected and processed for DNA-free RNA extraction. High quality RNAs were pooled and were sent to a commercial sequencing service provider for RNA-sequencing (RNA-seq). A total of 3.3Gb of RNA-seq data has been obtained and is currently being processed through data analysis workflows. The ultimate goal of this research is to generate the high-quality transcriptome of CRS to obtain insights into the insect’s biological traits. Further, the availability of molecular resources has potential to improve the existing strategies as well as to develop novel strategies to control CRS. In support of Sub-objective 2A, the methods described in 1C for preharvest pests were applied to better understand the release kinetics of stored product insect pheromones from various commercial formulations. The kinetic approach was easily extended to predict the potential for environmental loss of the lures. The kinetic data will now be used to reference improvement in lure longevity and will be coupled with attraction bioassays planned for 2022. All tested commercial formulations released pheromone at a rate that increased with temperature. Typically, these insect pests are more active in the early morning and/or dusk, when field temperature is moderate. Accordingly, pheromones will be modified to enhance water solubility for formulation as aqueous gel lures, which are known to release maximally at the times of highest insect activity, inversely related to temperature. Also in support of Sub-objective 2A, an experiment examined the effect of direct exposure to mating disruption dispensers on the mating of Indian meal moth. Exposure to mating disruption dispensers for as little as two hours was sufficient to reduce mating for the rest of a 10-hour dark period. Subsequent experiments found that re-emission from surfaces and commodity after a mating disruption dispenser was removed was also sufficient to reduce mating, but that the direct exposure to mating disruption dispensers was sufficient to reduce mating even when exposure and mating assays take place in different arenas. These experiments demonstrated that direct exposure to a concentrated source of pheromone is sufficient to prevent males from mating over an entire night. In support of Sub-objective 2C, research was initiated to understand the brown marmorated stink bug (BMSB)’s physiological response to Ethyl formate (EF) exposure. Ethyl formate is currently being investigated as a methyl bromide alternative for postharvest treatment of fresh and dried fruits, stored grains, cut flowers, and cargo exports. ARS researchers evaluated the EF fumigation of adult BMSBs for various durations and estimated the fumigant concentration to cause the known insect mortality. These data will provide the basis for genome-wide analysis of gene expression in BMSB following the EF exposure. Identification of various genes involved in a BMSB’s physiological response to EF exposure will not only improve the understanding of EF’s mode of action but also will provide insight into potential mechanisms for insect resistance to fumigants. In support of Sub-objective 3B, experimental procedures and modeling techniques developed by ARS researchers were used to assess the efficacy, fate, and transport of EF over the course of treatment, storage, and marketing. Research results enhanced the understanding of how this postharvest fumigant impacts human health, particularly pathways of applicator, worker, and by-stander exposure. Experiments were designed in collaboration with the Environmental Protection Agency (USEPA) and California Department of Pesticide Regulation. Results were presented to these government action agencies from the perspective of worker exposure and environmental impacts to support registration activities. This research critically supported mandatory reviews by California and USEPA and guided Occupational Safety and Health Administration standards. No publications were allowed due to data proprietorship. Also in support of Sub-objective 3B, a quarantine treatment utilizing sulfuryl fluoride was developed targeting navel orangeworm (NOW), almond moth (AM), and Mediterranean flour moth (MFM), which are quarantine insect pests in California almonds exported to India, valued at ca. 2 billion USD annually. ARS, in concert with USDA trade directors, established a postharvest fumigation with sulfuryl fluoride to control these pests, providing an alternative to fumigation with methyl bromide, which is globally regulated, and phosphine, which requires many days for efficacy. Developing this alternative fumigant supports phosphine-resistance management as well as compliance with the Montreal Protocol and reducing the Quarantine Preshipment use of methyl bromide, ARS Strategic Plan Goal # 3, “Crop Production and Protection”, USDA Animal and Plant Health Inspection Service Strategic Plan Goal # 3, “Facilitate safe U.S. agricultural exports”, and USDA-Foreign Agricultural Service Strategic Plan Goal #2, “Expand US agricultural exports through implementation of trade supporting initiatives”.

Accomplishments
1. Disentangling the effects of the male accessory glands in Mexican fruit fly females. Mexican fruit fly is a serious threat to production and export of several U.S. fruit commodities. An ARS researcher in Parlier, California, in collaboration with researchers at the College of Wooster, Wooster, Ohio, The Ohio State University, Wooster, Ohio, and other international collaborators in Mexico and Argentina, documented the impact of male accessory gland (MAG) products on female reproductive physiology. A comparative transcriptomics approach revealed that the MAG products regulate several female processes, such as egg development, chemosensory perception, host attraction, immune response, muscle development and lifespan. These research findings will contribute towards designing improved monitoring and control tactics against Mexican fruit fly.

2. Extended impact of short exposure of Indian meal moth to mating disruption dispensers. The Indian meal moth is a world-wide insect pest and considered the most economically important pest of processed foods. An ARS researcher in Parlier, California, in collaboration with a visiting scientist from Rajarata University of Sri Lanka, used a novel assay system to facilitate replicated studies examining the impact of commercial mating disruption dispensers on Plodia interpunctella. Both direct and indirect exposure to passive mating disruption dispensers for as little as two hours suppressed mating throughout the rest of a 10-hour night. This is the first direct evidence that for P. interpunctella, transient exposure to commercial mating disruption dispensers is sufficient to suppress male orientation to females without re-exposure to the mating disruption dispensers. An improved understanding of mechanisms for mating disruption can improve both development of future products and how current products are used.

3. Recapture of sterile navel orangeworm in an area-wide program. The navel orangeworm is the most important insect pest of the $8 billion dollar almond and pistachio crops in California, and currently millions of dollars are budgeted annually toward developing a sterile insect technique program for navel orangeworm based on the technology and infrastructure used to eradicate another moth pest, the pink bollworm, in cotton. ARS researchers in Parlier, California, in collaboration with colleagues from University of California, Riverside, and the USDA Animal and Plant Health Inspection Service, demonstrated significant recapture of sterile mass-released navel orangeworm in 2020 under conditions in which such recapture was negligible in 2018. Questions remain about efficiency of recapture of mass-released navel orangeworm and their impact for crop protection, but these results show important progress in production and delivery of healthy and competitive mass-released moths.

4. Mating disruption and reduced-risk insecticides provide synergistic control of the navel orangeworm. The navel orangeworm is the most important insect pest of the $8 billion dollar almond and pistachio crops in California. Mating disruption is widely used to control this pest, but industry seeks to further expand the role of this environmentally friendly technique in overall management of navel orangeworm. ARS researchers in Parlier, California, in collaboration with a colleague from private industry, used a 10-year data set from an overall area of 2400 acres of commercial almonds comparing plots treated with mating disruption only, insecticide only using a reduced risk ovi-/larvicide, or both. The two treatments together yielded significantly lower navel orangeworm damage than either over the entire study, and this trend was evident in nine of the 10 years in the study. Demonstration that mating disruption enhances control with a widely-used insecticide will boost its adoption by the tree nut industry.

5. Insecticide application drift reduction using synchronized air-blast sprayers. Pesticide drift is the airborne movement of pesticides away from the intended target and is of particular concern when an orchard is adjacent to buildings, waterways, or to crops where the pesticide is unregistered. A collaborative project involving an ARS researcher in Parlier, California, scientists from the University of California, and California Dept of Food and Agriculture evaluated the feasibility of drift mitigation using paired air blast sprayers to create an air barrier at the orchard’s edge, as well as the use of single sprayers with one air intake closed. Off-site insecticide movement was measured as far as 400 feet from the orchard edge. Differences in wind speed and wind direction were controlled and the single sprayer significantly reduced off-site drift, while the synchronized sprayers did not improve drift, but did improve coverage. These findings will serve as a foundation for future studies to improve insecticide application and precision, thereby simultaneously improving crop protection and minimizing off-site movement of pesticide.

Review Publications
Wilson, H., Burks, C.S., Reger, J.E., Wenger, J.A. 2020. Biology and management of navel orangeworm (Lepidoptera: Pyralidae) in California. Journal of Integrated Pest Management. 11(1):1-15. https://doi.org/10.1093/jipm/pmaa025.
Reger, J., Wenger, J., Brar, G., Burks, C.S., Wilson, H. 2020. Evaluating response of mass-reared and irradiated navel orangeworm, Amyelois transitella (Lepidoptera: Pyralidae) to crude female pheromone extract. Insects. 11(10):703. https://doi.org/10.3390/insects11100703.
Van Steenwyk, R.A., Siegel, J.P., Bisabri, B., Cabusaly, C.S., Choi, J.M., Steggall, J.W., Mace, K.C., Blecker, S.W., Poe, P.A., Peters-Collaer, S.R., Klassen, P. 2020. Spray drift mitigation using opposing synchronized air-blast sprayers. Pest Management Science. 77(2):895-905. https://doi.org/10.1002/ps.6094.
Sajeewani, P.H., Dissanayaka, D.K., Wijayaratne, L.W., Burks, C.S. 2020. Changes in shape, texture and airflow improve efficiency of monitoring traps for Tribolium castaneum (Coleoptera: Tenebrionidae). Insects. 11(11):778. https://doi.org/10.3390/insects11110778.
Rajarapu,, S.P., Bansal, R., Mittapelly, P., Michel, A. 2020. Transcriptome analysis reveals functional diversity in salivary glands of plant virus vector, Graminella nigrifrons. Gene. 11(11):1289. https://doi.org/10.3390/genes11111289.
Sparks, M., Gundersen, D.E., Bansal, R., Oppert, B.S., Poelchau, M.F., Childers, C., Rhoades, J.H., Velamuri, A.S., Benoit, J.B., Chao, H., Blackburn, M.B., Johnston, J. 2020. Brown marmorated stink bug, Halyomorpha halys (Stål), genome: underpinnings of polyphagy, insecticide resistance potential and biology of a top worldwide pest. BMC Genomics. https://doi.org/10.1186/s12864-020-6510-7.
Calla, B., Demkovich, M.R., Gomes-Viana, J.P., Siegel, J.P., Walden, K.K., Robertson, H.M., Berenbaum, M.R. 2020. Selective sweeps in a nutshell: the genomic footprint of rapid insecticide resistance evolution in the almond agroecosystem. Genome Biology and Evolution. 13(1). https://doi.org/10.1093/gbe/evaa234.