Sugar in Moderation: Variable Sugar Diets Affect Short-Term Parasitoid Behavior

Authors: LIGHTLE, DANIELLE - Oregon State University; AMBROSINO, MARIO - Oregon State University; Lee, Jana

Submitted to: Physiological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2009
Publication Date: 1/27/2010
Citation: Lightle, D., Ambrosino, M., Lee, J.C. 2010. Sugar in moderation: variable sugar diets affect short-term parasitoid behavior. Physiological Entomology. 35:179-185.

Interpretive Summary: The Apanteles wasp is an important parasitoid of orange tortrix caterpillars in raspberry and blackberry fields. Sugar sources in the fields are expected to improve the rate of attack on the caterpillars. Laboratory studies were conducted to look at how feeding affected the decision making of these wasps. Female wasps were either starved or fed a low or high concentrate sugar solution, and these feeding regimens were reflected in the amount of sugar measured in the gut of the wasps. When females were given the option of choosing between food scents or host scents, fed females selected host scents but starved females were just as likely to select food scents as host scents. Next, females were placed into a small plastic arena with 20 orange tortrix caterpillars. There were no differences in the number of eggs laid or the number of caterpillars attacked by the wasps. However, the wasps that had selected the host scents earlier tended to lay more eggs than the other wasps.

Technical Abstract: The biological control potential of parasitic wasps in the field is expected to increase with provisioning of sugar sources, which increase longevity and replenish carbohydrate reserves. Apanteles aristoteliae Viereck is an important parasitoid of Argyrotaenia franciscana (Walsingham), the orange tortrix, an economic pest in fruit crops. The effect of sugar diet on the physiological status of A. aristoteliae is studied in the laboratory, as well as the effects of physiological status on short-term olfactory orientation and parasitism behavior, and the association between olfactory orientation and immediate parasitism activity. Levels of glycogen, fructose, total sugars, proportional weight gain, and volume consumed are higher among females fed 25% sucrose solution than 10%, and lowest for those fed water. Lipid levels are unexpectedly highest among water-fed starved wasps. Sugar feeding also affects behaviour: wasps with higher levels of fructose or weight gain are less likely to make a choice in the olfactometer. Wasps with intermediate fructose levels or weight gain are more likely to orient towards hosts than wasps with low or high fructose levels. Among wasps that make a choice in the olfactometer, wasps fed 10% or 25% sucrose significantly prefer host versus food cues, while starved wasps are just as likely to select food as host cues. Females that orient towards host cues in the olfactometer are then marginally likely to oviposit more in hosts when introduced into an arena with host larvae.