Tobacco Budworm Control with Various Formulations of Bacillus Thuringiensis, 1987

Flue-cured tobacco was transplanted at the Central Crops Research Station, Clayton, N.C., on 6 May in a Norfolk loamy sand. Plots of 4 rows (45-inch row centers) × 60 ft (35 plants) were arranged in a randomized complete-block design for a test containing 10 treatments and 4 replicates. On 16 Jun, 15 uniformly sized and undamaged plants from each of the 2 left-most rows in each plot were tagged and infested with a single 2-day-old laboratory-reared tobacco budworm larva. Larvae were transferred to the plant bud with a camel’s hair brush. Two rows provided an untreated buffer. Treatments were applied with a C02-pressurized sprayer on 18 Jun through a single D2-33 full-cone nozzle per row at the rate of 25 gal/acre and 60 psi. Five and 11 days after treatment, the number of surviving larvae on the tagged plants as counted. After 13 days, budworm feeding damage was rated (0-4), and leaf consumption (0.1 leaves consumed) was estimated on all tagged plants/plot. On 10 Jul, all plants in the buffer rows were cut off at 3-4 leaves above the ground. Suckers grew from the axils of the remaining leaves, and on 29 Jul all but one healthy sucker were removed. Due to the presence of a naturally occurring budworm population, 20 plants containing a single small larva (<3rd instar) were selected and tagged on 12 Aug. Treatments were applied on 13 Aug as described above. Four- and 11-day counts of surviving budworms were made on tagged plants. A 14-day damage rating (0-4) was made on 27 Aug. Prior to ANOVA, count data were transformed to . Treatment means were separated using the Waller-Duncan K-ratio i-test (K = 100, α = 0.05). Means of untransformed data are presented.