Insect Management in Burley Tobacco in Non-traditional Areas of North Carolina

Abstract

Since the end of tobacco price supports in 2004, tobacco growers in eastern North Carolina have been investigating new agricultural enterprises, including burley tobacco. It is unknown if the pests and diseases common to flue-cured tobacco will be equally problematic for burley tobacco growers in eastern North Carolina. Research was conducted to determine the insect and disease pressures on burley tobacco. Studies were conducted over a two year period at the Central Crops Research Station, the Lower Coastal Plains Research Station, North Carolina State University greenhouses, and in commercial tobacco fields in eastern North Carolina counties. Incidence of tomato spotted wilt virus (TSWV), an economically important plant virus transmitted by thrips, was examined. Surveys of commercial burley tobacco fields revealed higher TSWV incidence in burley tobacco compared to flue-cured tobacco. Results from field studies also showed TSWV incidence was higher in burley tobacco compared to flue-cured tobacco under several agronomic conditions. Tobacco plants treated with imidacloprid had lower TSWV incidence than those plants left untreated. Tobacco plants transplanted temporally near major thrips flights had higher TSWV incidence than those transplanted to avoid major thrips flights. In the greenhouse, mechanically inoculated burley tobacco generally had the highest rate of TSWV infection; infection rates decreased as plant age increased. Colored adhesive traps were used to determine the attraction of thrips to varying colors of burley, flue-cured and Maryland tobaccos. Color is most likely only a minor contributing factor to higher TSWV incidence in burley tobacco. The presence of Heliothis virescens, the hornworm complex (composed of Manduca sexta and Manduca quinquemaculata), and Epitrix hirtipennis in burley and flue-cured tobaccos was compared. H. virescens showed preference for flue-cured tobacco over burley tobacco; hornworm complex larvae and E. hirtipennis showed no preference for either tobacco type. H. virescens numbers were higher in plots treated with imidacloprid, while E. hirtipennis numbers were lower in these plots. Hornworm complex larvae showed no preference for treated or untreated plots. Hornworm complex larvae exhibited no preference for a particular transplant date, while E. hirtipennis numbers were lower in plots assigned a late transplanting date. H. virescens showed preference for different transplant dates at the two locations. The effect of M. sexta larvae in open-air burley curing structures on cured burley yield was assessed. Larvae that enter the curing structure near the fourth instar cause the greatest yield loss to curing burley tobacco plants.