Research Project: Advancing Molecular Pest Management, Diagnostics, and Eradication of Fruit Flies and Invasive Species

Location: Tropical Pest Genetics and Molecular Biology Research Unit

2022 Annual Report

Objectives
Objective 1: Increase the effectiveness of sterile insect techniques for pest management including the development of next generation methods to achieve sterility, advances in mass insect rearing, and new combinations of techniques for cost-effective suppression and eradication of tephritids. Sub-objective 1A: Improvement of tephritid strains by characterizing strain domestication and colony infusions by quantifying the genetic and phenotypic effects and changes in microbial communities. Sub-objective 1B: Appraisal of Sterile Insect Technique strains for efficacy and efficiency. Objective 2: Identify pathways and risk factors for invasive tropical pest introduction, improve pest surveillance and detection methods, and analyze pest population dynamics at multiple levels to increase the protection of agriculture in Hawaii and the U.S. mainland. Sub-objective 2A: Identify attractant for female oriental fruit fly using host fruit volatiles associated with oviposition. Sub-objective 2B: Develop tools for pathway analysis of invasive Bactrocera and other tropical pests to improve bio-surveillance methods. Sub-objective 2C: Evaluate improvements to Male Annihilation Technique under low prevalence scenarios via changes in application density and pattern.

Approach
Research Goal 1A: Quantify the effect of cycling rearing temperatures, colony infusion protocols, and domestication on fly quality as determined by previously established performance metrics (flight ability, locomotor activity, adult longevity, time to sexual maturity, and fecundity) and microbial community diversity. Research Goal 1B: Evaluate current methods and develop standardized protocols for appraising the efficacy of mass-reared sterile flies in suppressing wild populations that can be used as a standard to determine if a new strain is able to be adopted. Hypothesis 2A: Host fruit odor based female attractant attracts more oviposition-ready females than odor from torula yeast. Hypothesis 2B: Genome-wide population genomics across the geographic range of emerging Bactrocera species, along with other tropical pests, will allow development of SNP-based source estimation along with other tools that can be applied to detection surveys, and improve the understanding of pathways of these invasive pests and improved control. Hypothesis 2C: An application density of half of the standard for male annihilation technique (currently 600 spots per square mile) will be at least as effective at killing male B. dorsalis.

Progress Report
This research project focuses on foundational and applied research towards improving control and detection of fruit fly pests and other tropical pest species. This progress report covers the first year of the newly established project 2040-22430-028-000D, “Advancing Molecular Pest Management, Diagnostics, and Eradication of Fruit Flies and Invasive Species” which includes Objectives 1 and 3 which were split from project 2040-22430-027-000D, titled, “Development of New and Improved Surveillance, Detection, Control, and Management Technologies for Fruit Flies and Invasive Pests of Tropical and Subtropical Crops” due to the creation of the Tropical Pest Genetics and Molecular Biology Research unit. Overall, this project supports current fruit fly eradication and exclusion programs throughout the United States by developing improvements to treatments, lures, trapping, and detection. In support of Sub-objective 1A, colony infusions following the protocols described in projected plan have been performed out to the third generation and the first round of phenotype data is being collected for both infused melon fly and oriental fruit fly genetic sexing lines. Additionally, with the addition of the new Research Biologist focusing on microbial ecology, culturing of bacteria associated with wild and laboratory populations of tephritid fruit flies is underway and an initial collection of greater than 250 isolates has been established and identified with 16S-ribosomal ribonucleic acid (rRNA). Protocols for long-read microbiome profiling of flies have been developed. Evaluation of gut microbial population dynamics of laboratory and fruit infested flies have indicated dramatic shifts in population densities within 48 hours of adult eclosion. Establishment of axenic rearing protocols have been assessed and development of microbe-free pupae are manageable. Reintroduction of bacteria to adults for functional analyses are ongoing. Minimal progress was made on Sub-objective 1B due to limited access to the ability to sterilize and release flies to perform the suppression trials. Cooperators in Guatemala did perform some overflooding experiments to support this objective at their facility. In support of Sub-objective 2A, fruits that were more attractive to mated female oriental fruit flies (OFF) than torula yeast bait were selected as original materials to develop synthetic chemical lure targeting mated female OFF. In two- and multiple-choice laboratory bioassays, we found guava juice, mango, and Surinam cherry most attractive to mated female OFF. We collected headspace volatiles from guava juice, mango and Surinam cherry and conducted gas chromatography (GC) electroantennographic detection (EAD) analyses using female OFF antennae. There were 16, 27, and 11 volatiles chemicals that were EAD-active (i.e., detected by antennae) with some overlap among different host fruits. Those EAD-active chemicals were identified using gas chromatography-mass spectrometry (GC-MS) and verified using authentic standards. Ratio of different chemicals in the headspace of each host fruit were determined to formulate guava juice, mango, and Surinam cherry blends for laboratory bioassays and field trapping experiments. Sub-objective 2B has been focused on generation of genome-wide single nucleotide polymorphism (SNP) datasets to assess population structure. Subsequent analysis shows little genetic diversity across the geographic range sampled, and we are working to expand the collections of these two Bactrocera species to better represent the global distribution of these flies across their native and invasive ranges. In support of Sub-objective 2C, researchers from Hilo, Hawaii, together with USDA, Animal Plant and Health Inspection Service (APHIS) and the California Department of Food and Agriculture (CDFA) colleagues executed “Mark-Release-Recapture” experiments with sterile Oriental fruit fly in southern California in August and September 2021. These confirmed previous published results indicating that lower “male annihilation technique” (MAT) density is more effective than the current standard. A single replicate has been executed in June 2022 near Sarasota Florida in collaboration with USDA, APHIS and the Florida Department of Agriculture and Consumer Services (FDACS). A final replicate is planned in July in Florida to complete the dataset for publication. This data supports the below accomplishment demonstrating the lower MAT density in application to support fly eradication and detection.

Accomplishments
1. State of Florida increased effectiveness by reducing application density of Male Annihilation against invasive oriental fruit fly. An eradication program was initiated on June 16, 2022, in Florida, in response to an incursion by the invasive oriental fruit fly. As a result of research by scientists in Hilo, Hawaii, plus their collaborators at USDA-Animal Plant and Health Inspection Service (APHIS), California Department of Food and Agriculture (CDFA), and Florida Department of Agriculture and Consumer Services (FDACS), a lower application density of the key control measure known as “Male Annihilation Technique” was used for the first time. Four hundred fifty (450) spots per square mile instead of the usual 600 were applied, which resulted in cost savings for materials and labor and reduced the amount of insecticide being applied, as well as simultaneously increasing effectiveness. The State of Florida and USDA-APHIS aim to make this reduction in application density permanent.

Review Publications
Sim, S.B., Curbelo, K.M., Manoukis, N., Cha, D.H. 2022. Evaluating Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) response to methyl eugenol: Comparison of three common bioassay methods. Journal of Economic Entomology. 115(2):556–564. https://doi.org/10.1093/jee/toac018.
Stockton, D.G., Cha, D.H., Loeb, G.M. 2021. Does habituation affect the efficacy of semiochemical oviposition repellents developed against Drosophila suzukii? Environmental Entomology. 50(6):1322-1331. https://doi.org/10.1093/ee/nvab099.
Faal, H., Cha, D.H., Hajek, A.E., Teale, S.A. 2021. A double-edged sword: Amylostereum areolatum odors attract both Sirex noctilio (Hymenoptera: Siricidae) and its parasitoid, Ibalia leucospoides. Fungal Ecology. 54. Article 101108. https://doi.org/10.1016/j.funeco.2021.101108.
Roh, G.H., Cha, D.H., Park, C.G. 2021. Olfactory attraction to aggregation pheromone is mediated by disti-flagellum of antennal segments in Riptortus pedestris. Journal of Asia-Pacific Entomology. 24:415-420. https://doi.org/10.1016/j.aspen.2021.01.005.
Pinero, J.C., Souder, S., Cha, D.H., Collignon, R.M., Vargas, R.I. 2021. Age-dependent response of female melon fly, Zeugodacus cucurbitae (Diptera: Tephritidae), to volatiles emitted from damaged host fruits. Journal of Asia-Pacific Entomology. 24(3):759-763. https://doi.org/10.1016/j.aspen.2021.06.011.
Tait, G., Mermer, S., Stockton, D.G., Lee, J.C., Avosani, S., Abrieux, A., Anfora, G., Beers, E., Biondi, A., Burrack, H.J., Cha, D.H., Chiu, J., Choi, M.Y., Cloonen, K., Crava, C.M., Daane, K., Dalton, D.T., Diepenbrock, L., Fanning, P., Ganjisaffar, F., Gomez, M., Gut, L., Grassi, A., Hamby, K., Hoelmer, K.A., Ioriatti, C., Isaacs, R., Klick, J., Kraft, L., Loeb, G.M., Rossi-Stacconi, M.V., Nieri, R., Pfab, F., Puppato, S., Rendon, D., Renkema, J., Rodriguez-Saona, C., Rogers, M., Sassu, F., Schoneberg, T., Scott, M., Seagraves, M., Sial, A., Van Timmeren, S., Wallingford, A., Wang, X., Yeh, D., Zalom, F., Walton, V.M. 2021. Drosophila suzukii (Diptera: Drosophilidae): A decade of research towards a sustainable integrated pest management program. Journal of Economic Entomology. 114(5):1950-1974. https://doi.org/10.1093/jee/toab158.
Sim, S.B., Corpuz, R.L., Simmonds, T.J., Geib, S.M. 2022. HiFiAdapterFilt, a memory efficient read processing pipeline, prevents occurrence of adapter sequence in PacBio HiFi reads and their negative impacts on genome assembly. Biomed Central (BMC) Genomics. 23. Article 157. https://doi.org/10.1186/s12864-022-08375-1.
Chen, B., Mason, C.J., Peiffer, M., Zhang, D., Shao, Y., Felton, G.W. 2022. Enterococcal symbionts of caterpillars facilitate the utilization of a suboptimal diet. Journal of Insect Physiology. 138. Article 104369. https://doi.org/10.1016/j.jinsphys.2022.104369.
Mason, C.J., Peiffer, M., St Clair, A., Hoover, K., Felton, G.W. 2021. Concerted impacts of antiherbivore defenses and opportunistic Serratia pathogens on the fall armyworm (Spodoptera frugiperda). Oecologia. 198:167-178. https://doi.org/10.1007/s00442-021-05072-w.
Mason, C.J., Ray, S., Davidson-Lowe, E., Ali, J., Luthe, D., Felton, G. 2022. Plant nutrition influences resistant maize defense responses to the fall armyworm (Spodoptera frugiperda). Frontiers in Ecology and Evolution. 10. Article 844274. https://doi.org/10.3389/fevo.2022.844274.
Shelly, T.E., Manoukis, N. 2022. Mating competitiveness of Bactrocera dorsalis (Diptera: Tephritidae) males from a genetic sexing strain: Effects of overflooding ratio and released females. Journal of Economic Entomology. 115(3):799-807. https://doi.org/10.1093/jee/toac027.