Impact of ascorbic acid fortification on the effectiveness of biological control agents

Ascorbic acid content is one of the nutritive parameters researchers are trying to enhance in plants. This study investigated the effect of altering dietary ascorbic acid concentrations in the host larvae of a beneficial wasp, Euplectrus comstockii and a baculovirus AcMNPV. Life history parameters of the wasp and infection rates of the virus were measured when larval Heliothis virescens reared on diets varying in ascorbic acid concentrations served as the host. Odds and odds ratio analyses showed that the probability of egg hatch and adult emergence for the wasp increased with the amount of ascorbic acid in the diet of the host. In contrast, larvae reared on ascorbic acid deficient diet experienced far higher levels of mortality following per os infection with AcMNPV. Additionally, viral infection in larvae fed an ascorbic acid-free diet, as monitored by epifluorescence microscopy, showed signs of infection much earlier than larvae fed control levels of ascorbic acid. Collectively, this indicates that as the ascorbic acid concentration is increased in the pest insect (and perhaps as the ascorbic acid concentration in the plant is increased) the effectiveness of microbial pathogens is likely to decrease, but the effectiveness of the wasp is likely to increase.