Project : USDA ARS

ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Chemistry Research » Research » Research Project #430032

Research Project: Insect, Nematode, and Plant Semiochemical Communication Systems

Location: Chemistry Research

2019 Annual Report

Objectives
1. Develop new improved attractants for weevils (Anthonomus pepper and cranberry weevils and Sitophilus maize and rice weevils) based on combinations of host plant kairomones and/or aggregation pheromones. 2. Develop pheromones and kairomones to improve the efficacy of mass-reared entomophagous nematodes used in biocontrol. 3. Develop new technologies to detect and control invasive arthropod pests. 3A. Develop kairomone-based attractants and repellants to control arthropod pests of honey bees, including the Varroa mite and the small hive beetle. 3B. Identify microbe-generated semiochemicals that influence insects or microbes, for example nectar microbes that increase pollinator visits to flowering crops. 3C. Identify volatile biomarkers for insect-infested crop products, such as fruit fly infested tomatoes, bananas, and mangoes.

Approach
Develop new and improved attractants for pest weevils based on combinations of host plant kairomones and/or aggregation pheromones. Develop pheromones and kairomones to improve the efficacy of mass-reared entomophagous nematodes used in biocontrol. Develop and test host plant volatile- and/or pheromone-based attractants and/or repellants to control arthropod pests of honey bees, including varroa mite and small hive beetle. Elucidate kairomone-based communication systems of tephritid fruit flies and the impact of kairmones on accelerated development of sexual signaling and reproductive maturity. This research will utilize numerous interactive laboratory- and field-based bioassays with insects, mites, nematodes, and plants, as well as purified biochemicals and other organisms. Isolation and identification of new bioactive chemicals that mediate arthropod and nematode behaviors and plant-arthropod/nematode interactions will be achieved using a combination of approaches including preparative GC, HPLC, preparative flash chromatography, GC-MS, FT0IR, NMR, micro-degradation, and synthesis where applicable. Major target insects for this research will include pest Coleoptera and Diptera that attack fruit and vegetable, Coleoptera and Acarina that impact honey bees, and Nematoda that control root insects. Other target insects may be selected as needed during progression of the project.

Progress Report
Natural sources for potential, minor cranberry weevil pheromone components were explored. One of the two identified compounds was determined to be a biosynthetic intermediary, and thus likely not an insect pheromone component. No natural source was found for the second (acidic) component, and thus synthesis should be considered if the existing pheromone blend need further improvement. To our knowledge this has not been described for this or other weevil species. A collaborator to field test new attractants is being sought. The pepper weevil oviposition deterring multicomponent pheromone blend has now been fully identified and the blend is being optimized for significant reduction in oviposition in laboratory choice tests. Non-host plant signals are being evaluated to further improve the oviposition deterrent blend. A crude, non-optimized host plant derived attractant blend is being field tested in south Florida. Potent deterrents and attractants are necessary for successful push-pull pest control. Host related attractants were characterized and shown to have significant importance in successful entomopathogenic nematode host infestation. We discovered that only a subset of nematodes needed to be primed on host related signals to promote pheromone guided host searching and mass infestation. We also discovered that a nematode-produced pheromone blend, that we previously discovered to induce dispersal from a consumed host insect, promoted general host searching behavior and improved infectivity of host insect. The goal is to train artificially-reared nematodes using specific plant- and host-insect cues prior to field application. In collaboration with local beekeepers and researchers at the University of Florida, ARS scientists have field tested an attract-and-kill bait for in-hive control of the small hive beetle. This strategy attracts beetles to an in-hive trap with a feeding attractant/stimulant where a toxicant is delivered when the insect consumes the edible bait. The development of an inexpensive small hive beetle trapping system is essential for in-hive control of this devastating pest. This technology will give our beekeepers control of this pest species that is affecting honey bee survival throughout the world. Our research objective was to gain knowledge and disseminate this information regarding current cultural practices in honey bee husbandry and better management of small hive beetles. In collaboration with researchers at University of Florida, Gainesville, Florida ARS scientists investigated the volatile emissions of microbes found on fruit after Spotted Wing Drosophila (SWD) foraging. SWD are major insect pests of numerous agricultural commodities. Bioassays using SWD and individual microbes showed that certain microbes attracted SWD and others repelled/inhibited SWD. Statistical analysis of the volatile profiles of an attractive microbe and a repellent microbe showed distinct differences. Further investigation of the volatiles may lead researchers to compounds that can be used in blends to inhibit SWD from visiting numerous host crops, or attract SWD to traps. Volatile emissions, sugar and amino catabolism, and honey bee preferences have been evaluated in single and binary mixtures of nectar microbes in synthetic nectar by Gainesville, Florida ARS scientists and in collaboration with colleagues at the University of California, Davis. In nature, nectar may be host to very high cell densities of microbes, yet nectar typically only contains 1-2 species. When microbes were co-inoculated to a synthetic nectar, volatile emission was dominated by yeast-derived volatiles, but all microbe inoculated nectars could be distinguished based on volatiles alone. Honey bees exhibited preferences among microbial solutions, consuming more of the bacteria-inoculated nectar compared to the yeast-inoculated nectar or the mixture, suggesting that the paradigm that nectar yeasts are generally more acceptable to pollinators than bacteria may be overly simplistic. These results are the first to describe volatile emission, primary metabolite catabolism, and pollinator response to nectar microbe mixtures. The effects of drought stress on floral traits, including floral volatiles, and nectar and pollen rewards, as well as native and managed pollinator preferences were evaluated by Gainesville, Florida ARS scientists, with researchers at the Mandan, North Dakota ARS location, and the University of Florida. Buckwheat, often grown as a groundcover or a forage plant for honey bee or cattle, was selected as the crop for study. Honey bees preferentially foraged on well-watered plants relative to drought-stressed buckwheat. Floral volatile composition was changed by drought stress, with increased emission of four volatiles known or suspected to be related to abiotic stress. The volume of nectar offered by drought stressed buckwheat plants was lower and contained a relatively higher proportion of monomers to sucrose. Honey bees typically prefer sucrose-rich nectars. Pollen count was the only floral trait found to be unaffected by drought stress, perhaps due to its dual importance as a pollinator reward and as the genetic material needed for plant reproduction. Finally, buckwheat seed set was reduced in drought stressed plants, with or without pollination by bees. An improved understanding of the potential affects drought may play on agricultural commodities is necessary as their intensity and frequency is anticipated to increase in the future. An agricultural floral nectar system, sunflower (Helianthus annuus), was selected for inoculation with identified nectar microbes due to its value as an edible crop (confection seeds and oil), biofuel crop, livestock forage, and as an ornamental cut flower. Resultant volatile emission profiles revealed previously identified nectar microbe semiochemicals that were not present in the headspace of non-inoculated control flowers. These microbe-derived volatiles were detected both in the headspace of extracted nectar as well as in the entire floral context, the latter being the first such direct detection of microbe-emitted volatiles in a floral nectar. After receiving APHIS approval, field experiments to screen pollinator preference among sunflowers inoculated with nectar microbes will be conducted. In collaboration with local growers, and other ARS and APHIS scientists, have investigated infestation of local, seasonal fruit with the insect pest Caribbean fruit fly, Anastrepha suspensa. The odors/volatiles emitted by the infested fruit were analyzed and compared with non-infested fruit. Data provided by the analyses will be analyzed and volatile biomarkers signaling infestation will be identified. Detected biomarkers may provide researchers with specific volatile profiles that can be used by APHIS scientists to detect infested fruit that is in transit or being imported.

Accomplishments
1. Small hive beetle kairomone-based attractant. ARS researchers in Gainesville, Florida, have developed an attract-and-kill bait for the in-hive control of the small hive beetle. This control measure utilizes an attractant incorporated into an edible bait. The attractant has been so successful in attracting small hive beetles within the hive, it will be field tested for its efficacy outside the hive within the apiary. The service honey bees provide in pollination make for a $15 billion in value to agricultural crops each year. Pollination provides Americans with a diet that is plentiful in fruits, nuts, and vegetables. The small hive beetle is a major pest of the honey bee and has had a devastating impact on pollinator health in North America. The adult beetles and larvae cause destruction by consuming honey bee eggs, brood, pollen and honey. This has a major impact on the hive’s survival. A control measure that can manage the beetle population will offer our nation’s beekeepers a method of control of this pest species that is affecting honey bee survival throughout the world.

2. Evaluation of bumble bee olfaction and gustation preference for nectar microbe-inoculated nectars. In collaboration with scientists at the University of California, Davis and Utah State University, Gainesville, Florida ARS scientists evaluated the olfactory and gustatory preferences of bumble bees, a native pollinator important to agriculture, to nectar microbe-inoculated nectars. Interestingly, bumble bees exhibited contrasting preferences between gustation and olfaction when presented with differing microbe strains, preferring the odor of a bacteria, but preferentially feeding on a yeast. After being allowed to forage on both microbe-inoculated nectars, bees adapted their preferences and were more accepting of the odor of yeast-inoculated nectars. This research is a first step towards deciphering the many signals bees use to evaluate a potential food source and provides new insight to the importance of both dissolved and volatilized nectar microbe metabolites in bee preferences and decision making.

U.S. DEPARTMENT OF AGRICULTURE

Chemistry Research: Gainesville, FL