Submitted to: Journal of Insect Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/31/2011
Publication Date: 7/6/2012
Citation: Valadez-Lira, J.A., Alcocer-Gonzalez, J.M., Damas, G., Nunez-Mejia, G., Oppert, B.S., Rodriguez-Padilla, C., Tamez-Guerra, P. 2012. Comparative evaluation of phenoloxidase in different larval stages of four lepidopteran pests after exposure to Bacillus thuringiensis. Journal of Insect Science. 12(21): 1-11. Available online: insectscience.org/12.21. Interpretive Summary: Some insect pests can be controlled by microbial bioinsecticides, such as fungi and bacteria, but insects may be able to resist by mounting an immune response. We evaluated the expression patterns of one enzyme involved in insect immune response, phenoloxidase, in four lepidopteran (moth) pests. We found that there were significant differences in the production of phenoloxidase in different larval stages and between male and female insects. These studies will be used to determine if application timing of a bioinsecticide may enhance its performance.
Technical Abstract: Some lepidopteran insects are important agricultural pests, causing serious crop damage. Microbial entomopathogen-based bioinsecticides are considered effective pest control alternatives to synthetic chemicals. However, insects can defend against pathogens by innate mechanisms, including phenoloxidase (PHO) and antimicrobial peptides, among others. More importantly, the immune response to biopesticides in arthropods may be related to their lack of efficacy. In the present study, we evaluated the differences in PHO production by life-cycle phases of the lepidopteran insect pests Heliothis virescens, Plodia interpunctella, Spodoptera exigua, and Trichoplusia ni. Our results indicated significant differences in PHO production among larvae, pre-pupae, pupae and adults among all species. In general, all insects had a significantly higher PHO production in pre-pupae and pupae, compared with early-instar larvae and adults. When differences were observed between female and male, PHO production was higher in females. These results may be used to further investigate bioinsecticide performance in pest management strategies, and they may be useful particularly if application time is programmed accordingly to lower PHO production. However, more studies are needed to determine the relationship between PHO production and the susceptibility of an insect to a particular bioinsecticide.