Professor University of Vermont Burlington, Vermont
Swede midge, Contarinia nasturtii (Keiffer) (Diptera: Cecidomyiidae), is an invasive pest that causes severe losses for heading Brassica crops. Swede midge feeding severely damages susceptible crops, leading to plant deformation, unmarketable produce, and the complete loss of marketable heads. Due to the extreme susceptibility of host plants, management approaches need to target swede midge before they mate and oviposit on plants. In order to better suppress midge mating, we need to understand where swede midge mate within rotational vegetable systems. Some insect herbivores migrate to host plants before mating while others mate at the site of emergence and then migrate to oviposit on host plants. We tested how midge sex and mating status influenced their behavioral response to host plant and non-host plant odors. We used Y-tube olfactometer bioassays to assess how male, unmated female, and mated female swede midge respond to cauliflower (host plant) and non-host plants (artificial plant, tomato, and swiss chard plants). We found that mated female swede midge strongly prefer host plant volatiles. Additionally, we found that males and virgin females do not prefer host plant volatiles. Our results suggest that locating host plants is inconsequential to swede midge mating and female swede midge locate host plants after mating occurs.
