Testing prospective cover crops for conservation biocontrol to control cutworms in canola: color and odor preferences and longevity of Copidosoma bakeri (Hymenoptera: Encyrtidae)

Cutworms (Noctuidae) cause economic damage to several Canadian agricultural crops. The egg-larval parasitoid, Copidosoma bakeri (Hymenoptera: Encyrtidae), is likely to be the most effective parasitoid for controlling cutworms. However, the rate of parasitism is often too low to reduce cutworms below economic levels. Providing additional resources for parasitoids through habitat management has been shown as an effective method to increase parasitism rates in biocontrol agents. This study examined the potential utility of several prospective cover crops as additional nutritional resources for C. bakeri, to develop effective habitat management strategies. Based on flowering period and flower colour, several plants were chosen for testing, including: flax, oriental mustard, phacelia, chickling vetch, camelina, buckwheat, tillage radish, field pennycress and canola. All experiments were performed with both food-inexperienced (water fed) and food-experienced (honey fed) individuals.  Food-inexperienced wasps were preferentially attracted to canola, camelina, mustard and buck wheat. These four plants were then used in dual choice tests which were carried out to study visual and olfactory preferences of C. bakeri. Food in-experienced wasps were significantly attracted to yellow and demonstrated a significant preference for brassicaceae flowers over camelina and buckwheat. However, food-experienced parasitoids showed no preference for color or floral odour. We also demonstrated that C. bakeri females lived significantly longer on honey than on water alone and without food. Additionally, survival time of parasitoids on canola, camelina, mustard and buck wheat were similar to each other, but reduced relative to honey. Therefore, canola, camelina and mustard are not only attractive to C. bakeri, but also provide nutritional resources that improve lifespan. Future research will examine the effectiveness of these plant species for improving parasitism rates of C. bakeri on cutworms in the field.