Location: Commodity Protection and Quality Research
2023 Annual Report
Objectives
The long-term objective of this project is to improve the quality of specialty crops grown in the western U.S. and increase their domestic consumption and export. All three objectives represent multiple, integrated issues focused on reducing insect damage, maintaining or improving quality and ensuring that exported commodities meet all phytosanitary requirements. Project integration will facilitate successful implementation of systems-based control strategies into current crop production systems, delay the development of resistance to chemicals used for control or disinfestation, overcome trade barriers for the export of fresh fruits and nuts, and minimize deleterious effects of these chemicals on the environment.
Objective 1: Develop new or improved preharvest processes that are acceptable to industry and regulatory partners that reduce the incidence of pests in fresh and durable commodities prior to harvest.
Sub-objective 1A: Improve current integrated pest management strategies for control of navel orangeworm (NOW) in order to reduce damage and minimize nontarget impacts on environmental quality.
Sub-objective 1B: Reduce NOW damage to almond and pistachio orchards by characterizing the environmental and host factors associated with high NOW damage to orchards and develop strategies to eliminate them or mitigate their impact.
Sub-objective 1C: Minimize chemical treatment requirements by characterizing and optimizing integrated pest management strategies for monitoring and control of key dipteran and lepidopteran pests.
Sub-objective 1D: Improved management of pests of high-value commodities through generation of molecular resources and development of genomics-based approaches.
Objective 2: Develop new or improved postharvest processes for the control of arthropod pests, such as handling procedures and treatments, that contribute to food security and food safety while maintaining commodity quality.
Sub-objective 2A: Improve semiochemical-based strategies for control of stored product insect pests.
Sub-objective 2B: Develop novel postharvest treatments for fresh and durable commodities that maintain or improve commodity quality while protecting the commodity against arthropod pests.
Sub-objective 2C: Improve the sustainability of methyl bromide alternatives using molecular toxicology approaches to understand pest physiology, in the context of emergence of insecticide resistance.
Objective 3: Ensure that new treatments comply with environmental, human health, sanitary, and phytosanitary regulations, including local, state, national, and international regulations.
Sub-objective 3A: Develop treatments for action agencies and industry that satisfy the regulatory requirements of the exporter and importer, ensuring that technology implementation results in market retention or expansion.
Sub-objective 3B: Identify agrochemical use strategies and develop novel technologies to ensure residues are compliant with importer and domestic food tolerances.
Sub-objective 3C: Develop technologies that reduce or eliminate atmospheric emissions during ventilation of postharvest fumigations to address air quality criteria.
Approach
This project has one overarching theme, maintaining or improving the quality of west coast horticultural commodities in order to maintain or expand market share, by improving existing systems approaches and developing new ones. This complex project contains three objectives, 10 sub-objectives, and 13 research goals. The research focus of Objective 1 is preharvest, and three sub-objectives and four research goals target the navel orangeworm (NOW), the primary moth pest of California tree nuts. Research will evaluate the feasibility of a nonchemical alternative, sterile insect technique and facilitate the integration of another nonchemical technique, mating disruption, into existing management programs. These programs will be improved by enhancing the efficacy of existing insecticides through changes in timing and improvements in coverage, as well as recognizing orchards at increased risk for damage. The final NOW sub-objective determines the feasibility of using RNAi-mediated reduction in target gene expression to improve its control, as well as that of citrus red scale. The final sub-objective in Objective 1 seeks to improve the monitoring and control of dipteran pests such as the spotted wing drosophila, the Mediterranean fruit fly, and the melon fly, by improving existing attractants and developing new ones.
The research focus of Objective 2 is improved control of coleopteran and lepidopteran pests of fresh and durable commodities in storage. It contains three sub-objectives and four research goals. The first sub-objective and two research goals are far ranging and involve novel methods to synthesize semiochemicals and develop new methods to dispense them. Additional studies seek to improve mating disruption using the same semiochemicals for both disruption and detection. The final two sub-objectives and two research goals are independent but related to one another. One sub-objective is quite broad; developing novel postharvest treatments for fresh and durable commodities. The control methods assessed include low oxygen controlled atmosphere, cyanide, sulfuryl fluoride, phosphine, and ethyl formate, alone and in combination, as well as irradiation. The focus of the final sub-objective is to identify the insect genes responsible for both ethyl formate toxicity and the combination of ethyl formate and CO2 used as an additive, in brown marmorated stinkbug, in order to improve control.
The research focus of Objective 3, which contains three sub-objectives and four research goals, is to ensure that the techniques and technologies developed in the earlier objectives can be adopted. The first sub-objective and research goal ensures that treatments developed for lepidopteran and dipteran pests are in compliance with all pertinent regulations. The second sub-objective and two research goals focuses on generating efficacy and residue data to support the use of ethyl formate and sulfuryl fluoride as substitutes for methyl bromide. The final sub-objective and research goal focuses on developing recapture technologies to reduce or eliminate fumigant emissions into the atmosphere.
Progress Report
In support of Sub-objective 1A, an ARS scientist in Parlier, California, conducted a replicated mark-release-recapture experiment in 160-acre pistachio plots to compare the recovery and dispersal of sterile navel orangeworm (NOW) from the Phoenix Mass Rearing Facility (PRF). Sterile NOW were transported from PRF to USDA-ARS Parlier in a van with active temperature control. Both percent recovery of males and the dispersal distance of females were improved in the newer mass release strain “MCS” as compared to the older mass release strain “P”. However, in all cases the percent recapture was less than 0.5 percent (%) and the median distance traveled was less than 300 feet. Compared to previous studies with this and other moth species in sterile insect technique programs, the improvement is incremental and further work is needed to obtain more suitable moth performance.
In further support of Sub-objective 1A, an ARS scientist in Parlier, California, conducted field trials to continue assessing the coverage obtained from reducing water volume from 100 gallons to 70 gallons per acre using organosilicone adjuvants. Trials tested 70 gallons of water per acre at an adjuvant concentration of 0.1%, using the diamide insecticide chlorantraniliprole compared to a control treatment using 100 gallons per acre. These treatments were assessed over three weeks and the treatment using 70 gallons of water per acre was successful. Air application using the pyrethroid fenpropathrin at 15 gallons of water per acre was also assessed. Considerable variability in efficacy among blocks was observed and these trials will be repeated. An additional trial assessing autonomous sprayers was conducted in Fresno County, evaluating insecticides applied using 100-200 gallons of water per acre. Although the treatment using 200 gallons of water per acre produced the highest mortality, the treatment using 100 gallons per acre was acceptable and further trials will be conducted.
In support of Sub-objective 1B, an ARS scientist in Parlier, California, collected data from orchards in Fresno County participating in a sterile release program for navel orangeworm, the primary lepidopteran pest of California almonds. The information included data on insecticide use and insect trapping data for 2020-2022. Analysis of these data is ongoing, and damage and population density data will be compared to research conducted between 2016-2020 assessing sanitation failure (presence of unharvested nuts) and its mitigation. Creating a baseline will facilitate the multiyear process of identifying indicators for both high and low insect damage. Ongoing research to determine the efficacy of sanitation programs and assess insect damage contributes to a reduction of the navel orangeworm population.
In support of Sub-objective 1C, the release kinetics of four isoprenyl ether analogs from polymeric lures were evaluated in the laboratory and the field. Releases in the laboratory increased as temperature increased, and a predictive Arrhenius relationship was modeled. This kinetic approach was tested, and ultimately validated in the field, using weather data and polymeric lures; the actual release was within 10% of the predicted value. Effective lures are required for trapping spotted wing drosophila and understanding the field dissipation of the lure is critical to improve capture. ARS scientists in Parlier, California, transferred the results to USDA Animal and 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, an assay to introduce double-stranded RNA (dsRNA) orally for RNA interference (RNAi) in navel orangeworm (NOW) was developed and standardized. Exploratory trials involving different insect diets and various dsRNA concentrations were performed. This was followed by a standardized assay utilizing NOW larvae feeding on a lima bean-based diet containing 500 ng dsRNA of target gene per mg diet. Each NOW neonate was confined individually in a 0.5 ml tube and supplied with 500 mg diet. Measurements of gene expression in treated insects revealed approximately 60 to 80% reduction in transcript levels of target genes at 9- and 15-days post exposure. Standardization of feeding assays for oral delivery of dsRNA supports foundational research to investigate gene function, which is required to develop field management tools.
In support of Sub-objective 2A, hydrolyzable precursors of cigarette beetle and cow pea weevil beetle pheromones were synthesized by ARS scientists in Parlier, California. The acetate precursor, (Z)-7-hydroxy-4,6-dimethylnon-2-en-3-yl acetate, was synthesized with 85% yield, then purified and formulated into cellulosic lures for use in forthcoming bioassays with cigarette beetle females. The chemical glucopyranosyl (Z)-3-methyl-3-heptenoate was synthesized with 90% yield, then purified and formulated into cellulosic lures for use in forthcoming bioassays with cow pea weevil.
In further support of Sub-objective 2A, mating frequency of Indian meal moth (IMM) was compared between IMM pairs confined to arenas of 28 ml, 950 ml, or 208 liters. These experiments demonstrated mating rates of 50% in the smaller arenas regardless of light conditions. In the larger arena, mating of this nocturnal moth was 75% over night, but less than 25% during the day. Overnight mating in the larger containers was suppressed to less than 25% by a mating disruption dispenser. These and related experiments showed IMM males that closely approach dispensers are less effective at mating for the rest of the night, but that this effect can be overcome by close proximity of the sexes which can occur at high abundance.
In support of Sub-objective 2B, pilot-scale evaluations of fumigant toxicity were conducted, and the dosage, duration, and temperature parameters required to control 95% of a population using different fumigants were confirmed by ARS scientists in Parlier, California. Ethyl formate concentration-time (Ct) exposures at 20, 25, and 18 grams (g) per meter (m) for 3 hours (h) controlled 1,000 adult females of the flat mite species Tarsonemus bakeri, Brevipalpus californicus, and B. lewisi at 10 degrees C. A Ct exposure of 500 g m-3 h sulfuryl fluoride controlled 2,500 eggs of confused flour beetle at 10 degrees C. Cigarette beetle eggs were controlled when phosphine levels at 10 degrees C were maintained between 0.7 and 1.5 g m- 3 h for four days. Eggs of the cigarette beetle at 28 degrees C were also controlled when oxygen levels less than 2% were maintained for four days.
In support of Sub-objective 2C, research continued to identify various genes and molecular pathways involved in ethyl formate (EF) toxicity to insects. An ARS scientist in Parlier, California, investigated the molecular response of brown marmorated stink bug (BMSB) to EF fumigation. Nondiapausing BMSB adults were exposed to EF at headspace concentrations of 18 and 27 mg/ l/ h for 8h at 10.0 degrees C without any additive. Gene expression analysis of treated insects revealed several differentially expressed genes implicated in various basic biological roles at cellular and molecular levels. This research contributed towards improving the sustainability of methyl bromide alternatives, such as EF, using molecular toxicology approaches to understand pest physiology related to the emergence of insecticide resistance.
In support of Sub-objective 3A, pilot-scale evaluations of fumigant toxicity against selected pests were conducted. Dosage, duration, and temperature parameters required to control 95% of specimens in the target pest population were confirmed by ARS scientists in Parlier, California. A concentration-time (Ct) exposure of 170 g m-3 h methyl bromide controlled larvae of Oriental fruit fly and blueberry maggot feeding inside blueberries at 15 degrees C. A Ct exposure of 20 g m-3 h hydrogen cyanide controlled 3,000 internally feeding larvae of Mexican fruit fly in citrus at 10 degrees C. Approximately 3,000 Western cherry fruit fly larvae were controlled when phosphine levels at 8 degrees C were maintained between 0.7 and 1.5 g m-3 h for five days.
In support of Sub-objective 3B, ARS scientists in Parlier, California, published results of evaluations on the efficacy of ethyl formate towards BMSB, and a suite of other insect pests. New Zealand and Australia used the published research results to establish a phytosanitary treatment that controls stink bugs and other “hitchhikers” in imported vehicle consignments valued at $40 B USD annually.
In further support of Sub-objective 3B, ARS scientists in Parlier, California, used capillary electrophoresis with indirect ultraviolet detection and a fluoride-ion sensitive electrode to determine that residue levels of fluoride vary depending on the commodity undergoing sulfuryl fluoride treatment, as well as the fumigation schedule. However, less than 10% residual standard deviation (RSD) in residue levels were observed across replicate fumigations of a given commodity and schedule.
Accomplishments
1. Asian citrus psyllid control using ethyl formate. Asian citrus psyllid (ACP) is a devastating pest of citrus, as it spreads the disease Huanglongbing that curtails fruit yield and quality. Southern California is impacted by ACP quarantines whereas the packing and juicing operations in the San Joaquin Valley of California are not. ARS scientists in Parlier, California, developed a postharvest fumigation treatment with ethyl formate to control ACP after fruit is binned and loaded on a trailer prior to transportation from the grove. This innovative treatment limits ACP spread and reduces broad-spectrum insecticide use. ARS scientists also developed an ethyl formate treatment that will begin replacing methyl bromide treatments of imported table grapes from Chile, which represents the greatest U.S. usage of this fumigant on fresh fruit. Data generated by this research was submitted to the US Environmental Protection Agency and California Department of Pesticide Regulation to support Section 3, Federal Insecticide, Fungicide, and Rodenticide Act registration.
2. Control of invasive and quarantine horticultural pests. Brown marmorated stink bug (BMSB) adults overwinter in container consignments and vehicles, many of which are exported to countries requiring a phytosanitary treatment to control this invasive insect pest that damages fruit, vegetable, and ornamental crops. In 2022, ARS scientists in Parlier, California, were asked to develop a treatment that could be applied on-arrival in Australia and New Zealand. An ethyl formate fumigation protocol was developed to control BMSB, resulting in market retention for the export of automobiles to Australia and New Zealand with a projected annual value of USD $10 billion.
3. Identification of insecticide resistance in Gill’s mealybug. The Gill’s mealybug (GMB) is a serious pest of pistachios in California. Insecticide treatment is the primary control method, but growers have experienced control failures since 2019. The cause of these failures was unknown. An ARS researcher in Parlier, California, screened field populations from the Central Valley of California, and found that a population from Hanford was resistant to acetamiprid. The insecticide resistance level identified in this research, although relatively low, indicated that there has been repeated pressure to select for acetamiprid resistance in GMB. Acetamiprid resistance levels can increase if effective GMB management steps are not taken which will decrease the ability to manage this pest. This information will alert growers that they need to rotate to a different insecticide family to delay resistance.
4. Field observations of the response of navel orangeworm males to synthetic pheromone lures. Determining the impact of the biological clock and external temperature on the timing of sexual activity of moth pests like the navel orangeworm is important for optimization of control technologies based on pheromone mating disruption. An ARS researcher in Parlier, California, in collaboration with colleagues from California State University, Fresno, and University of California, Riverside, gathered and analyzed two years of camera trap data to build on information from previous studies based only on field observations of males attracted by laboratory-reared females. Males exhibited the greatest sexual activity in the last few hours before sunrise in summer conditions and began mating earlier in cooler times of the year. Unlike previous reports, it was noted that peak time of capture changed with season but not with transient temperature changes. Improved understanding of day-night patterns of male activity will improve our understanding of monitoring data and enable optimization of mating disruption for the navel orangeworm. Improved control based on this understanding could reduce insecticide used to control this primary pest of almonds and pistachios planted on approximately 1.5 million acres of land with an annual farm gate value of nearly $8.5 billion.
5. Identifying pistachio hull factors associated with insect damage to improve quality. The navel orangeworm (NOW), Amyelois transitella, is the primary insect pest of pistachios, a specialty crop worth over $2.5 billion in California. Improving the understanding of NOW biology and interaction with its pistachio host is required to reduce damage by identifying high risk orchards. NOW controls costs more than $50 million annually. An ARS researcher in Parlier, California, conducted an 11-year study using processor grade sheet information to identify nut factors associated with increased insect damage. Two nut factors related to early hull split, percent adhering hull and dark staining, were strongly correlated with damage. An improved grower understanding of the management practices that cause early hull split, including irrigation practices, will reduce the frequency of its occurrence, thereby reducing insect damage and increasing nut quality.
Review Publications
Obenland, D.M., Leyva-Gutierrez, F., Wang, T. 2022. Investigations into determinants of blueberry coating effectiveness. Foods. 12(1). Article 174. https://doi.org/10.3390/foods12010174.
Burks, C.S., Hengst, F.S., Wilson, H., Wenger, J.A. 2022. Diel periodicity in males of the navel orangeworm (Lepidoptera: Pyralidae) as revealed by automated camera traps. Journal of Insect Science. 22(5). Article 11. https://doi.org/10.1093/jisesa/ieac059.
Obenland, D.M., Arpaia, M. 2023. Managing postharvest storage issues in ‘Shiranui’ mandarin. HortTechnology. 33(1):118-124. https://doi.org/10.21273/HORTTECH05133-22.
Bansal, R., Hunter, W.B., Haviland, D.R. 2023. Baseline susceptibility and evidence of resistance to acetamiprid in Gill’s mealybug, Ferrisia gilli Gullan (Hemiptera: Pseudococcidae). Journal of Economic Entomology. 116(2):554-559. https://doi.org/10.1093/jee/toad012.
Siegel, J.P. 2023. Nut factors associated with navel orangeworm, Amyelois transitella (Lepidoptera: Pyralidae) damage to pistachio (Pistacia vera) in California (2007-2017) and implication for control. Journal of Economic Entomology. 116(3):882-890. https://doi.org/10.1093/jee/toad051.
Goane, L., Carrizo, B., Ruiz, M., Bachmann, G.E., Milla, F., Segura, D., Kuzmich, D., Walse, S.S., Vera, M. 2023. Behavioural and electrophysiological response of Anastrepha fraterculus (Diptera: Tephritidae) to a gamma-lactone synthetic semiochemical. Insects. 14(2). Article 206. https://doi.org/10.3390/insects14020206.
Coates, B.S., Walden, K.O., Lata, D., Vellichirammal, N.N., Mitchell, R.F., Andersson, M.N., Mckay, R., Lorenzen, M.D., Grubbs, N., Wang, Y., Han, J., Xuan, J., Willadsen, P., Wang, H., French, B.W., Bansal, R., Sedky, S.F., Souza, D., Bunn, D., Meinke, L.J., Miller, N.J., Siegfried, B.D., Sappington, T.W., Robertson, H.M. 2023. A draft Diabrotica virgifera virgifera genome: insights into control and host plant adaption by a major maize pest insect. BMC Genomics. 24. Article 19. https://doi.org/10.1186/s12864-022-08990-y.
Corbett, S.M., Cullum, J.P., Abrams, A.E., Rodriguez, M.S., Leskey, T.C., Walse, S.S. 2023. Confirmatory evaluation of eFUME for control of brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae). Journal of Economic Entomology. 116(3):771-778. https://doi.org/10.1093/jee/toad064.
