Tobacco as a Trap Crop for Heliothis virescens (F.) (Lepidoptera: Noctuidae) in Cotton

A 3-yr study evaluated tobacco as a trap crop for the tobacco budworm, Heliothis virescens (F.), in cotton. Small plot experiments were conducted on an experimental farm at Mississippi State University in Starkville, MS, in 1996 and on a commercial farm in Aliceville, AL, in 1997 to determine the ability of small strips of tobacco to trap H. virescens in cotton field plots. In the 1996 experiment, tobacco budworms eggs were significantly higher on tobacco than on cotton from 7 June through 19 June and from 10 July through 22 July. In 1997, H. virescens eggs were significantly higher on tobacco than on cotton for every sampling date throughout the growing season. The conclusion derived from these small plot experiments was that H. virescens females preferred tobacco over cotton as an ovipositional site. Therefore, in 1998, a large-scale field experiment was conducted to determine the effectiveness of tobacco as a trap crop for H. virescens in commercial cotton fields in Funston, GA. In this experiment, the number of H. virescens eggs was significantly lower in cotton fields with tobacco trap crops compared to control cotton fields without tobacco trap crops on 2 and 9 July. Also, economic threshold for H. virescens was not reached in these cotton fields with tobacco trap crops. In contrast, the economic threshold for this pest was met in cotton fields without tobacco trap crops on two dates during the growing season. For each year of the study, percentage total real mortality (r_x) for eggs and larvae of H. virescens on tobacco was very high, ranging from 91.4–99.9%. Larval mortality was attributed in part to parasitization by Toxoneuron nigriceps (formerly Cardiochiles nigriceps) Viereck and Campoletis sonorensis Cameron and an infection by an ascovirus of H. virescens. Thus, tobacco served as a trap crop and sink for H. virescens in cotton in this study.