ASSESSMENT OF DRIP IRRIGATION APPLIED INSECTICIDES FOR LEPIDOPTERAN CONTROL IN TOBACCO, 2011

An experiment to compare the efficacy of drip irrigation applications of Coragen against lepidopterous pests in tobacco was conducted at Cross Creak Farms, near Raeford, NC. Coragen applications in tobacco are either made preventatively at transplant or as foliar treatments when insects reach economic thresholds. Preventative applications are attractive to growers, but efficacy varies in relation to insect infestation timing, particularly for TBW. Locations with access to drip applications could potentially make preventative applications after transplant, closer to anticipated TBW infestation. Eight, single row plots were established on 3 June, 3 weeks after transplant (WAT), and treatments were applied to alternating rows to achieve 4 replications. The untreated rows served as controls. Rows were 264 ft long and had between 129 and 136 plants each. Coragen was applied at 15 psi in 5.06 gal per row via a drip line with emitters every 12 inches. Plants were 22 inches apart and rows were spaced 46 inches, center to center. The irrigation system was run 45 minutes following application to clear the lines and ensure thorough wetting. Because TBW counts were unusually high, treatments were reapplied on 24 June. The number of TBW and the instar of each larva were observed weekly until topping. HW larvae were counted and separated by age on two sample dates following topping, 15 July and 29 July, but were only present in meaningful numbers on the first date. TBW data were analyzed via a repeated measures analysis of variance (ANOVA; SAS v. 9.3.1) with replicate as a random independent variable. HW data was analyzed via a one way ANOVA. Means were separated via by Fisher’s Protected LSD (α = 0.05).