DEVELOPMENT OF FIELD AND LABORATORY TECHNIQUES TO EVALUATE THE RELATIVE ATTRACTIVENESS OF CORN PLANTS TO CORN ROOTWORM BEETLES (DIABROTICA)

Studies were conducted to: (1) develop field and laboratory procedures and techniques for use in evaluating the relative attractiveness of inbred lines of corn to western corn rootworm beetles (Diabrotica virgifera virgifera LeConte); (2) compare the relative attractiveness of extracts prepared from specific plant parts (stalk, pollen, silk and leaf) of selected inbred lines of corn to western corn rootworm beetles; and (3) compare the relative attractiveness of selected inbred lines of corn to western corn rootworm beetles and to a lesser extent, northern corn rootworm beetles (Diabrotica barberi Smith and Lawrence). Beetle counts were used to provide data on the relative attractiveness of selected inbred lines of corn to corn rootworm beetles. The effectiveness of the beetle count method was compared to an Immigration-Planting technique in which sticky traps were used to sample corn rootworm populations immigrating into plantings of selected inbred lines of corn. The Immigration-Planting technique involves planting corn in a soybean field that does not have a corn rootworm larval infestation but is adjacent to a corn field with large numbers of corn rootworm beetles. Sticky traps were used in field studies to evaluate the attractiveness of 16 plant extracts (four inbreds x four plant parts) prepared from inbred lines H99, B73, N132 and N7AO(,2). Olfactometer studies of extract attractiveness were also conducted. Extract studies involved only female western corn rootworm beetles. The Immigration-Planting technique appeared to be a more effective measure of plant attractiveness in the field than periodic beetle counts. Extract studies reduced the influence of environmental factors. Results of extract studies in the field and in the olfactometer were similar. Extracts of stalk and pollen were consistently more attractive to female western corn rootworm beetles than were extracts of silk and leaf samples. Inbred line H99 was consistently among the inbred lines attracting the highest number of beetles and inbred N7AO(,2) was consistently among the least attractive