Location: Chemistry Research2017 Annual Report
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.
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.
This project is categorized into three objectives with three sub-objectives comprising objective 3. Considerable progress was made by Gainesville, Florida, ARS scientists to address the goals of the project. A critical vacancy within the research project led to the removal of objective 4 and the modification of objective 3 during the current fiscal year. For objective 1, the pheromone blend previously identified by Gainesville, Florida, ARS and Rutgers University scientists for the cranberry weevil has successfully been field tested in combination with an optimized trap design. It should now be possible to replace very labor intensive sweep netting with trap monitoring of weevil populations. For the pepper weevil, an improved analyses of pepper fruit with or without pepper weevil oviposition plugs revealed new information on the complex blend of free fatty acids in the oviposition plugs, as well as additional volatile compounds. We previously identified the oviposition deterring pheromone as a two-component blend that offered no significantly increased fruit protection in field trials. However, we anticipate this may change with the addition of minor pheromone components. Also, a labile sesquiterpene was previously identified by ARS scientists as a crucial addition to a host plant-based attractant blend. A scaled-up extraction of a natural source for this sesquiterpene was unsuccessful. A new screening for an alternative natural source identified a common weed that can be extracted to produce sufficient amounts of a partially purified sesquterpene for field assays of a new attractant blend. We anticipate that in Florida this attractant can be successfully used for prior and in-between field season trapping and reduction of the pest insect population to give an acceptable level of crop loss without pesticide applications. Finally, important bioassays were performed on a number of plants and their ability to elicit a response from the maize weevil. The host plant corn demonstrated an ability to attract the weevil. For objective 2, Gainesville, Florida, ARS scientists have continued to utilize the previously isolated entomopathogenic nematode (EPN) attractant, pregeijerene, as a tool for nematode behavioral studies. Using results from the behavioral studies, it was discovered that: EPNs exhibited an innate attraction to pregeijerene; EPNs can learn to respond to varying volatile cues; and, different species of EPN can cross communicate. The ARS scientists also discovered a previously unknown host searching group behavior that appear to be of crucial importance for successful host infection. To utilize these discoveries, ARS scientists developed an improved design of in-soil sampling probes that will be used for lab and field collection of root volatiles released by different plant species and cultivars under biotic and abiotic stress. In a collaborative effort, Gainesville, Florida, and Byron, Georgia, ARS scientists are developing a strategy to prime artificially reared EPN on root produced attractants prior to field release, thus improving their infectivity of pest insects. For objective 3A, Gainesville, Florida, ARS scientists have isolated the aggregation pheromone for the small hive beetle that will be used in a pheromone-based trapping system. The pheromone, which has a patent pending issuance, will be used to develop a trapping system used for attracting and capturing small hive beetle adults. The isolated pheromone, along with a fruit volatile blend, is attractive and successful in trapping the small hive beetle. This discovery has the potential to control an invasive species that is affecting honey bee nationwide. ARS scientists, in collaboration with scientists from International Centre of Insect Physiology and Ecology (ICIPE) in Nairobi, Kenya, have investigated the adult grooming rate, brood removal rate and Varroa mite infestation levels on the savannah honeybee, Apis melifera scutellata in Kenya and of the European honeybee hybrid Apis mellifera in the United States. Three newly discovered types of mite damage were identified in mites from the USA honey bees that contributed significantly to the overall damage recorded. The information collected is a significant step towards understanding the adaptive processes of Varroa mite resistance in honeybees worldwide. ARS scientists are investigating the chemical signals involved in the mite’s attraction to honey bee drones, which are preferred for reproduction. Once identified, the biologically active compounds will be incorporated into a trapping system and made available to our nation’s beekeeping industry for effective control measures for management of the Varroa mite. In an effort to better understand small hive beetle behavior within a honey bee hive, ARS scientists investigated the effects of providing the beetle with prepared commercial pollen substitutes. This study examined the potential effects of commercial pollen substitutes on the survivability and reproductive success of the small hive beetles. The research objective was to gain knowledge and disseminate this information in regards to current cultural practices in honey bee husbandry and better management of small hive beetles. For objective 3B, Gainesville, Florida, ARS scientists, in collaboration with a University of California, Davis researcher have developed a robust standard method for the evaluation of nectar microbes on a synthetic nectar. Additionally, the ARS scientists developed a reliable standard method for identifying microbe-produced volatiles that may be signaling chemicals to honey bees. These methods will allow the ARS and UC Davis researchers to efficiently screen and investigate microbe-produced volatiles and their potential use as semiochemicals for pollinators. For objective 3C, Gainesville, Florida, ARS scientists, in collaboration with a University of Florida scientist, as well as other ARS and APHIS scientists, have performed studies on fruit fly infested peaches. Preliminary results have demonstrated that different cultivars of peaches emit different profiles as fruit fly larvae develop within the peach. These results, if confirmed after further studies, will allow researchers to use volatile biomarkers to identify peaches that are infested with fruit fly larvae and safely remove them from the food supply. In collaboration with other ARS scientists, Gainesville, Florida, ARS scientists evaluated and reported on volatiles from fungal-contaminated almonds and pistachios. These biomarker volatiles can provide growers and researchers a means to detect contaminated nuts within storage areas and an early warning signal for their removal prior to being processed for human consumption.
1. Entomopathogenic nematode (EPNs) host searching behavior. Nematodes can be both a major plant pest as well as beneficial to plants, and their behavior is to a large extent controlled by pheromones, which are typically odors sensed by other nematodes. A patent was issued to ARS researchers in Gainesville, Florida, California Institute of Technology and Cornell University scientists for the use of ascaroside pheromones for attraction and repulsion of both pest and beneficial nematodes. Gainesville, Florida, ARS scientists discovered that beneficial EPNs also are attracted to plant produced odors and that the nematodes can be trained to respond to new and other plant odors. Additionally, it was discovered that the tested beneficial nematodes express a group behavior that can lead to successful infection of host insects. Thus, in addition to pheromones we now have new tools in the form of plant-produced odors to improve the use of beneficial nematodes in biological control, as well as a potential use for control of plant parasitic nematodes.
2. Attractant for navel orangeworm. Insect pests can vector toxin-producing microbes into their agricultural hosts. A second patent was issued to an ARS researchers in Gainesville, Florida, for a host plant-based volatile blend that attracts the insect pest navel orangeworm in almond orchards. Navel orangeworm larvae vector toxigenic microbes into tree nuts. A private company (Wonderful Orchards) has initiated an application for licensing this ARS-developed technology. 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 where moth populations are to warrant protective measures.
3. Microbe-emitted odors attract pollinators. With the decline in honey bee health, new research is needed to help pollinators locate and pollinate agricultural commodities. ARS researchers in Gainesville, Florida, scientists, in collaboration with a University of California, Davis researcher, have identified volatiles produced by microbes in nectar that influence pollinator behavior. Their research showed that microbes are common, but variable in nectar, and that certain microbial species produce distinct volatile blends that influence honey bee preference. These results provided a potential new tool for farmers and researchers to improve yields of their pollinated crops.
4. Host plant odors attract the maize weevil. The maize weevil, Sitophilus zeamais is an important insect pest of stored grains, predominantly corn, wheat, rice, and sorghum. Currently, the only control method is the application of an insecticide applied to the grain, with no effective trapping system for maize weevils. In an effort to better understand this behavior, ARS researchers in Gainesville, Florida, have investigated the weevil’s attraction to dry grains, as well as the weevil’s preference to lay eggs on specific host grains. Preliminary results demonstrated that the strongest attraction for males and females was corn. Results from this research will aid in determining which odors initiated the greatest attraction with a focus on isolating these odors to be used in developing a trapping system. A novel, inexpensive method for monitoring and control of the maize weevil would significantly reduce loss due to this pest.
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