Submitted to: Naturwissenschaften
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2009
Publication Date: 6/17/2009
Citation: Tunaz, H., Stanley, D.W. 2009. An Immunological Axis of Biocontrol: Infections in Field-Trapped Insects. Naturwissenschaften. Available: http://www.springerlink.com/content/y052745140721x46/fulltext.pdf/. Interpretive Summary: Application of classical insecticides has introduced severe problems in agricultural sustainability. The concept of biological control of insects is a potentially powerful alternative to classical insecticides. Biological control is based on the idea that direct application of insect-specific pathogens and parasites can reduce pest insect populations and the economic damage due to pest insects. The problem, however, is the efficiency of these organisms in biological control programs is limited by insect immune defense reactions to challenge. However, the extent to which insects become infected with biocontrol agents has not been adequately documented. To address, we are investigating insect immune reactions in nature. In this paper we document natural infections in field-trapped insects. We show for the first time that virtually all insects become infected by bacteria and fungus in nature. This new research will be directly useful to scientists who are working to improve the efficacy of biological control methods. The ensuing improved biological control methods will benefit a wide range of agricultural producers by supporting the long-term sustainability of agriculture.
Technical Abstract: We report results of a field study designed to assess the extent of natural microbial infections in insects collected from agrarian fields. Pest species were collected from fields surrounding Kahramanmara', Turkey. The specimens were identified and dissected under a microscope to assess numbers of nodules in the insect bodies. Formation of darkened, melanized nodules is the predominant cellular immune reaction to microbial infection and once formed, the nodules are permanently attached to internal surfaces. The presence of melantoic nodules within the collected specimens was taken as evidence of past microbial infections from which the specimens had recovered. The collected insects were healthy as judged by behavioral observation, turgidity of larvae, and feeding activity. Of the >400 examined specimens, at least some nodules were found in 98%. Numbers of nodules ranged from ~2/individual to >100 nodules/individual. Most insects experience and recover from natural microbial infections in the field. The key implication of our finding is that insect immune effector systems limit the host range and effectiveness of microbial agents deployed for biological control. Future advances in the efficacy and use of biopesticides will depend on understanding and somehow attenuating insect innate immune effector systems. Some insect pathogens have already evolved effective mechanisms to achieve this advance.