Location: Chemistry Research
2018 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
Odors from blueberry buds have been collected, analyzed and identified. Herbivory-induced changes in the volatile profile may explain why weevils are more attracted to damaged plants, and the addition of volatile components to the pheromone blend were tested. The pepper weevil blend that was based on plant odors now includes herbivory-induced sesquiterpenes. In laboratory-based trapping studies, this blend attracted both male and females weevils, with a preference to attract males. Other minor blend components were considered in addition to non-chemical cues. The sesquiterpene used was isolated from natural sources and has not been completely purified. Studies are ongoing to purify this compound and re-evaluate its efficacy for trapping the pepper weevil. For ovipositional deterrents, additional components from oviposition plugs have been identified and various blends formulations were tested. For the maize weevil, various host plants have been evaluated and results suggest that rice plants provide the strongest attraction of male and female weevils. Assays to determine what specific compound(s) are ongoing. The development of an attractant blend is important for trapping and controlling these insect pests while reducing the need for pesticide applications.
Continued to study semiochemical-based entomopathogenic nematode behavior. To better understand how blends of odors change as a function of distance from the roots, ongoing research is determining how different root odors interact with soil particles and water content. Additionally, simple bioassays have been designed and will be utilized for the formulation of attractive pheromone and host plant blends. The ability to influence the behavior of entomopathogenic nematodes can help control other agricultural root insect pests.
Investigating the chemical semiochemical indicators involved in the attraction of Varroa destructor to larva and honey bee drones, which are preferred for reproduction. The biologically active compounds will be incorporated into a system for trapping the mite, thus reducing the mite population within the hive. This technology will be made available to our nation’s beekeeping industry for effective control measures for management of this invasive pest.
Expanded the previously-developed protocol for identifying chemicals that act as honey bee signaling chemicals to include identification of non-volatile metabolites dissolved in nectar. Plant-derived non-volatile nectar components can play important roles in both plant and pollinator outcomes. The metabolites excreted by nectar specialist microbes have not yet been reported in the literature. Identifying these extracellular metabolites is an important first step towards evaluating and developing a floral microbe-based biocontrol method that improves pollinator and plant fitness.
Additionally, ARS researchers have expanded our system to include binary mixtures of natural nectar microbes. In nature, nectar may be host to very high cell densities, but typically only contains 1-2 species. These so-called priority effects, where early arriving microbes suppress the growth of later-arriving species, is also reported in floral nectar. These methods will allow the ARS and UC Davis researchers to efficiently screen and investigate microbes and the potential uses of their metabolites as semiochemicals and sources of nutrition for pollinators.
ARS researchers have begun a new collaboration with researchers at the Mandan, North Dakota ARS location and the University of Florida to evaluate the effects of drought stress on floral traits, including floral volatiles and nectar and pollen rewards, as well as native and managed pollinator preferences. The selected crop, buckwheat, is often grown as a forage plant for honey bee or cattle. Preferences between drought-stressed and well-watered buckwheat plants will be evaluated with bumble bee/greenhouse bioassays and filed-based experiments with honey bees and native insects. An improved understanding of the potential effects drought may play on agricultural commodities is necessary as their intensity and frequency is anticipated to increase in the future.
In collaboration with local growers, and other ARS and APHIS scientists, have established a protocol for infestation of local, seasonal fruit with the Caribbean fruit fly Anastrepha suspensa, as well as subsequent analysis of the odors emitted by the infested fruit. Comparison of the infested versus non-infested fruit may provide researchers with specific odors that can be used by APHIS scientists to detect infested fruit that is in transit or being imported. A robust protocol was needed in order to apply toward other insect pests and other agricultural commodities.
Accomplishments
1. Attractant for the insect pest navel orangeworm. Insect pests can vector toxin-producing microbes into their agricultural hosts. ARS researchers at Gainesville, Florida had two ARS patents (patent Nos. 9,655,366 and 9,220,261) licensed (LN 1726-001) by a private company for commercialization. Navel orangeworm larvae vector toxigenic microbes into California tree nuts (ca. $5 billion annually). The blend attracts both male and female adult moths in both conventional and mating disruption-treated almond orchards, which allows growers to more accurately determine when moth populations are such as to warrant protective measures.
2. Varroa mite reproductivity. In collaboration with researchers from ICIPE in Nairobi, Kenya, ARS researchers at Gainesville, Florida, have investigated if the fertility, fecundity and numbers of mated female offspring of the mite, Varroa destructor, can explain the reduction in reproductive success of mite in the African honeybee, Apis melifera scutellata. Results indicated that reduced mite reproductive success may explain the slow mite population growth in African honey bee colonies. This research is a significant advancement in the understanding the adaptive processes of varroa mite reproduction in honeybee subspecies worldwide.
3. Orchid floral fragrances and pollinators. ARS researchers at Gainesville, Florida, in collaboration with researchers at the University of Florida have identified and characterized a novel series of odor compounds associated with the floral fragrance of an endangered native, epiphytic orchid, Prosthechea cochleate (clamshell orchid). Orchids represent the most valuable floriculture crop produced in the United States and are highly valued for their potential as genetic resources in producing hybrids for floriculture. Results from this study help provide a better understanding of the reproductive biology and pollinator attraction to the clamshell orchid and may thus allow for increased propagation efforts, as an increase in pollination would result in more seed capsule production and increase the number of flowering plants. Additional research investigated the pollination of Encyclia tampensis, the butterfly orchid, by various insect taxa in south Florida. The ability to successfully propagate orchids on a large scale has contributed greatly to conserving germplasm for availability to the floriculture industry.
Review Publications
Nganso, B.T., Fombong, A.T., Yusuf, A.A., Pirk, C.W., Stuhl, C.J., Torto, B. 2018. Low fertility, fecundity and numbers of mated female offspring explain the lower reproductive success of the parasitic mite Varroa destructor in African honeybees. Parasitology. https://doi.org/10.1017/S0031182018000616.
Block, A.K., Vaughan, M.M., Christensen, S.A., Alborn, H.T., Tumlinson, J.H. 2017. Elevated carbon dioxide reduces emission of herbivore induced volatiles in Zea mays. Plant Cell and Environment. doi:10.1111/pce.12976.
Helms, A.M., Moraes, C.M., Troger, A., Alborn, H.T., Francke, W., Tooker, J.F., Mescher, M.C. 2017. Identification of an insect-produced olfactory cue that primes plant defenses. Nature Communications. 8(1):337. doi:10.1038/s41467-017-00335-8.
Ruan, W., Shapiro Ilan, D.I., Lewis, E., Kaplan, F., Alborn, H.T., Gu, X., Schliekelman, P. 2018. Movement patterns in entomopathogenic nematodes: continuous vs. temporal. Journal of Invertebrate Pathology. 151:137-143. https://doi:10.1016/j.jip.2017.11.010.
Block, A.K., Christensen, S.A., Hunter Iii, C.T., Alborn, H.T. 2017. Herbivore derived fatty-acid amides elicit reactive oxygen species burst in plants. Journal of Experimental Botany. doi:10.1093/jxb/erx449.
Christensen, S.A., Sims, J., Vaughan, M.M., Hunter III, C.T., Block, A.K., Willett, D.S., Alborn, H.T., Huffaker, A., Schmelz, E.A. 2018. Commercial hybrids and mutant genotypes reveal complex protective roles for inducible terpenoid defenses. Journal of Experimental Botany. doi:10.1093/jxb/erx495.
Alborn, H.T. 2018. A technique for thermal desorption analyses suitable for thermally-labile, volatile compounds. Journal of Chemical Ecology. 44(2):103-110. doi:10.1007/s10886-018-0924-6.
Silva, D., Kyryczenko-Roth, V., Alborn, H.T., Rodriguez-Saona, C. 2018. Comparison of trap types, placement, and colors for monitoring Anthonomus musculus (Coleoptera: Curculionidae) adults in highbush blueberries. Journal of Insect Science. 18(2):1-9. https://doi.org/10.1093/jisesa/iey005.
Kostromytska, O.S., Rodriguez-Saona, C., Alborn, H.T., Koppenhofer, A.M. 2018. Role of plant volatiles in host plant recognition by Listronotus maculicollis (Coleoptera: Curculionidae). Journal of Chemical Ecology. 44(6):580-590. doi:10.1007/s10886-018-0964-y.
Rering, C.C., Beck, J.J., Hall, G.W., Mccartney, M.M., Vannette, R.L. 2018. Nectar-inhabiting microorganisms influence nectar volatile composition and attractiveness to a generalist pollinator. New Phytologist. 220(3):750-759. doi:10.1111/nph.14809.
Cheseto, X., Kachigamba, D., Ekesi, S., Ndung'U, M., Teal, P.E., Beck, J.J., Torto, B. 2017. Identification of the ubiquitous antioxidant tripeptide glutathione as a fruit fly semiochemical. Journal of Agricultural and Food Chemistry. doi:10.1021/acs.jafc.7b03164.
Willett, D.S., Rering, C.C., Ardura, D.A., Beck, J.J. 2018. Application of mathematical models and computation in plant metabolomics. In Sarker, S.D., Lutfun, N., editors. Computational Phytochemistry. 1st edition. Netherlands, Amsterdam: Elsevier. p. 231-254.
Ray, H.A., Stuhl, C.J., Gillett-Kaufman, J.L. 2018. Floral fragrance analysis of Prosthechea cochleata (Orchidaceae), an endangered native, epiphytic orchid, in Florida. Plant Signaling and Behavior. 13(1):e1422461. doi:10.1080/155923424.2017.1422461.
Willett, D.S., Som, S., Alborn, H.T. 2017. Dynamics of belowground diffusion and diffusion and degradation. Rhizosphere 2004. 4:70-74. doi:10.1016/j.rhisph.2017.07.004.
Beck, J.J., Alborn, H.T., Block, A.K., Christensen, S.A., Hunter III, C.T., Rering, C.C., Seidl-Adams, I., Stuhl, C.J., Torto, B., Tumlinson, J.H. 2018. Interactions among plants, insects, and microbes: elucidation of inter-organismal chemical communications in agricultural ecology. Journal of Agricultural and Food Chemistry. 66(26):6663-6674. doi:10.1021/acs.jafc.8b01763.
Murungi, L.K., Kirwa, H., Coyne, D., Teal, P.E., Beck, J.J., Torto, B. 2018. Identification of Key Root Volatiles Signaling Preference of Tomato Over Spinach by the Root Knot Nematode Meloidogyne incognita. Journal of Agricultural and Food Chemistry. 66:7328-7336. doi:10.1021/acs.jafc.8b03257.
