Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 3, 2001
Publication Date: N/A
Interpretive Summary: Western tarnished plant bugs (Lygus hesperus) and their eastern counterparts, tarnished plant bugs (L. lineolaris) are major pests in many cropping systems in North America, costing hundreds of millions of dollars in damage each year. Furthermore, plant bugs are becoming increasingly resistant to conventional pesticides and require alternative means of control, including biologically based systems such as biological control and sterile insect techniques. However, such technologies require mass rearing based on artificial diets, and such diets require safe, reliable means of reducing microbial contamination and spoilage. Many of the old standby chemicals (such as formaldehyde) for prevention of microbial growth are either toxic to humans who rear the insects or destructive to the insects being reared. Therefore, we tested a panel of antifungal agents to find candidates that could be used in colonies of plant bugs. We found that propionic acid, benzoic acid, and sorbic acid have low toxicities to the Western tarnished plant bugs tested. These chemicals are safe enough to humans to be widely used in the food industry as food preservatives, so they are suggested as candidates to replace formaldehyde. This research is of benefit to the growing insect rearing community (commercial and government-based) in establishing techniques for efficiently rearing high quality insects with the lowest possible risk to insectary workers.
Technical Abstract: Artificial diets have become important components of rearing systems for insects that are used for research purposes and in commercial production. Because the rearing conditions for insects also provide ideal settings for mold growth, antifungal additives are often used to reduce diet contamination. However, the antifungal agents must not only be effective in mold suppression, they must also be safe to the target insects of the rearing programs. Five antifungal agents (benzoic acid, formalin, methyl paraben, propionic acid, and sorbic acid) were tested using diet bioassays on Lygus hesperus Knight, and the effect on biological fitness was measured. Biological fitness was defined as total number of survivors, mean biomass (dry weight) accumulated per cage over the total treatment period, egg production, time to adult emergence, and time to start of egg laying. Methyl paraben and formalin were found to have significant negative effects on these measurements of biological fitness. High concentrations of benzoic acid and sorbic acid also had significant negative effects on L. hesperus biological fitness. Challenge tests to determine the ability of the antifungal agents to suppress mold growth when inoculated into the diet medium are currently in progress.