Location: Biological Control of Pests Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Innovate new and established chemical approaches for management of imported fire ants in order to create new and more effective ways to control them. Sub-objective 1A: Search for new fire ant toxins from defensive chemicals in other ants. Objective 2: Develop improved formulations and new products for more effectively controlling floodwater mosquitoes using biological control agents and natural products. Sub-objective 2A: Determine key physiological processes in the embryonating and embryonated eggs that may suggest new ovicidal targets or markers. Sub-objective 2B: Discover biopesticides with ovicidal activity. Sub-objective 2C: Develop effective formulations of selected biopesticides/natural products with demonstrated ovicidal effects to enhance penetration and lethality.
1b. Approach (from AD-416):
Despite the effort in developing alternative control technologies, management of fire ants and mosquitoes has continued to have challenges associated with effectiveness, application strategy, and cost. New environmentally friendly biopesticides would make product handling easier, improve public acceptance, and potentially provide more effective control. For fire ants, we will search new toxins from defensive chemicals produced by other ants and develop double-stranded ribonucleic acid (RNA) toxins. New toxins will be used in bait, mound drench and immersion treatment. Floodwater mosquitoes have evolved a reproductive strategy in which females deposit their eggs in damp soil of flood prone areas. The temporary separation of eggs from water may provide an opportunity to control eggs without applying control agents directly into the water, thereby reducing their impact on non-target aquatic organisms. An effective ovicide would also make it possible to treat floodwater mosquitoes over a longer period of time before emergence, greatly improving the practicality of community based control programs. Our research on mosquitoes focus on discovering biopesticides with ovicidal activity by studying key physiological processes in the embryonating and embryonated eggs and on identifying new naturally occurring substances and pathogenic microorganisms which can disrupt those processes. A correct formulation will greatly enhance the penetration of biopesticides into insect eggs. By selecting the right adjuvant group and optimizing hydrophile-lipophile balance (HLB) numbers, the improved biological formulation should be able to attack the eggs of the targeted mosquitoes.
3. Progress Report:
Progress has been made in the following three areas: (1) toxic tolerance of imported fire ants to defensive compounds from other ants; (2) the mechanism of toxic tolerance in fire ants; and (3) developed a standard methodology to evaluate entomopathogenic fungi and natural products under laboratory conditions. Chemical control using synthetic insecticides are commonly used in controlling imported fire ants, including red imported fire ant and black imported fire ants. Knowledge on toxic tolerance of fire ants is important in developing effective chemical control products and methods. Progress has been made in understanding the toxic tolerance of the imported fire ants to synthetic insecticides and defensive compounds from other ants. Red imported fire ants have been found to be significantly more tolerant to insecticides and ant defensive compounds than the black imported fire ants. The mechanism of toxic tolerance in fire ants was also investigated. It was found that esterase activities in red imported fire ants were more than three times higher than those in the black imported fire ants. 2-tridecanone, an ant defensive chemical from tawny crazy ants, showed significantly greater inhibition to esterases in the black imported fire ants than those in red imported fire ants. In the current practice, chemical control technology in fire ant management is not species-specific. In other words, the same dose of active ingredient is usually recommended for both red imported fire ants and black imported fire ants. The differentiation of toxic tolerance should justify a different application dose of insecticides for these two ant species or at least warrant further investigation on this topic. Progress has also been made in the research on biological control of imported fire ants using pathogenic microorganisms. A standard methodology has been developed to evaluate entomopathogenic fungi and natural products under laboratory conditions.
1. Toxic tolerance of red imported fire ants and its mechanism. Synthetic pesticides are commonly used in fire ant control, which causes public concern about health and environmental problems. It is important to understand toxic tolerance of fire ant in order to develop more effective products and their application methods. Researchers at Stoneville, MS, found that the red imported fire ants are more tolerant to abiotic stresses including toxins than the black imported fire ants. Toxic tolerance may contribute to the invasion success of the red imported fire ants. The research also provided a justification to develop species specific chemical control technologies for control these two pest ants.
2. Standard methodology for evaluating entomopathogenic fungi and natural products against mosquitoe eggs. A method was developed for evaluating the effect of entomopathogenic fungi and natural products on mosquito eggs. The result showed the black salt marsh mosquito eggs were not susceptible to the tested entomopathogenic fungal strains, Beauveria bassiana GHA, Beauveria bassiana NI8, Metarhizium brunneum F52, and Metarhizium anisopliae ATCC 62176. However, there were significant differences in emergence among treatments of fire ant piperidine alkaloids. The highest concentration of 10ug/uL piperidines resulted in the lowest emergence rate.
Sakhanokho, H.F., Sampson, B.J., Tabanca, N., Wedge, D.E., Demirci, B., Husnu Can Baser, K., Bernier, U.R., Tsikolia, M., Agramonte, N.M., Becnel, J.J., Rajasekaran, K., Chen, J., Spiers, J.M. 2013. Chemical composition, antifungal and insecticidal activities of Hedychium essential oils. Molecules. 18:4308-4327.