Preliminary Results of Use of a Mark-release-recapture Technique for Determining the Sphere of Influence of a Kairomone-baited Lure Trap Attractive to Adult Western Corn Rootworms (Coleoptera: Chrysomelidae)

Abstract

The western corn rootworm, Diabrotica virgifera virgifera (LeConte)(Coleoptera: Chrysomelidae), continues to be one of the most costly insect pests of corn, Zea mays L., in the United States. It is estimated that the corn rootworm complex causes approximately $1 billion in crop losses and control costs annually in the U.S. (Metcalf, 1986). This pest also has recently been introduced into Europe. Urek (1998) stated that it was discovered in Serbia as early as 1990 and has since continued to spread throughout the European continent. For these reasons, it is increasingly important to develop an efficacious, user friendly system of monitoring this pest. Several types of western corn rootworm (WCR) monitoring techniques have been in troduced and studied over the past decades (Chiang, 1973; Hein and Tollefson, 1984; Hoffman et al, 1996; Luckmann et al, 1975; Musick and Fairchild, 1970; Shaw et al, 1984). Although these techniques have scientific value, several current monitoring tech niques (such as sticky traps) have met with resistance from producers and consultants because of the inconvenience associated with handling messy, sticky materials (G. Wilde, pers. obs.). Furthermore, visual plant inspections may yield varying population estimates because of differences in scout experience (Shufran and Raney, 1989), time of day or weather conditions (Lance, 1990). Since non-sticky, kairomone-baited traps are left in the field over a longer period of time, resulting captures are not necessarily affected by fluctuations in WCR activity levels caused by changes in weather or time of day. Assuming that the traps have been deployed properly, scout experience should also have less influence on beetle captures. Turchin and Odendaal (1996) employed both a single-release-multiple-trap design and a multiple-release-single-trap design to study the effective sampling area of a pheromone trap for Dendtroctonus frontalis Zimmerman (Coleoptera: Scolytidae). They suggested the single-release design was most suited for studying the long-distance probabilities of recapturing beetles. The multiple-release design was employed for their short-range studies to avoid underestimation of recapture probabilities due to overlap of attractive areas (Elkinton and Carde, 1980). Furthermore, Turchin and Thoeny (1993) suggested that traps closest to the release point would capture many of the released beetles, reducing the recapture probability at longer distances. A commercially available kairomone-baited lure trap (Trece, Inc., Salinas, CA) has been tested in field trials in Kansas to determine its effectiveness in monitoring adult WCR. Knowledge about the sphere of influence of a lure trap is important in deploying traps in the field and to avoid lure plume overlap during studies. We sought to develop a method of determining the sphere of influence for the Trece lure trap and to determine its effective