Effects of Anti-Fungal Compounds on Feeding Behavior and Nutritional Ecology of Tobacco Budworm and Painted Lady Butterfly Larvae

Mold control is one of the most vital issues in insect rearing systems because mold outbreaks can alter the nutritional value of diets, harm insects, and even threaten the health of insectary workers. Because antifungal agents are widely used in insect diets their potential harmful effects on target insects’ quality is a major concern. This concern stems from the observations reported in several publications that high levels of antifungal agents in diets affect growth, development, survival, and fecundity. These observations and many unpublished observations on several insect species reared in our laboratory led us to study the mechanisms underlying those deleterious effects, using two representative lepidopterans, a butterfly and a moth, Vanessa cardui and Heliothis virescens larvae reared on different concentrations of three widely used antifungal agents: methyl paraben, potassium sorbate and sodium propionate. These antifungal agents were administered in concentrations of 1,000, 5,000, and 10,000 parts per million (ppm). The results show that the highest levels of antifungal agents suppress nutrient absorption (ECI) and increase metabolic costs (ECD). Relative consumption rates (RCR) and digestibility (AD) increased with increasing antifungal agent concentration, possibly to compensate for the declines in absorption and metabolism. Also, to determine the potential for antifungal agents’ effects on diet acceptance, we experimented with feeding responses to the three concentrations used in these experiments, showing a decreases of acceptance of diets with high concentration of methyl paraben and slight increases in acceptance of high concentrations of potassium sorbate. Finally, because pH of diet is intimately related to effectiveness of antifungal agents, we included experiments on pH and diet acceptance, but within the narrow range of diet pH values tested, there were no preferences displayed.