Control of Tobacco Budworms with Foliar Insecticides, 1986

Flue-cured tobacco ‘var. K-373’ was transplanted at the Central Crops Research Station, Clayton, NC on 12 May in a field of Norfolk loamy sand. Plots 4 rows wide (45 inches on center) by 40 ft in length were arranged in a randomized complete-block design for a test containing 10 treatments and 4 blocks (Test I) and 9 treatments and 4 blocks (Test II). On 9 and 11 Jun (Test I and II, respectively) 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 transfered to the plant bud via a camel’s hair brush. The right-most rows provided an untreated buffer. Treatments were applied on 10 and 12 Jun (Test I and II, respectively) through a single D2-33 full cone nozzle per row at the rate of 25 gpa and a pressure of 60 psi. Three and 10 (Test I) and 4 and 11 (Test II) days post-treatment the surviving larvae on tagged plants were counted and after 14 days damage was rated in Test I as follows: 0 = no damage, 1 = light damage (holes < 1 cm), 2 = moderate damage (1 cm < holes < 6.4 cm), 3 = heavy damage (holes > 6.4 cm and on several leaves) and 4 = topped plant. Consumption was rated in Test II as 0.1 leaves consumed on all tagged plants per plot. On 7 and 25 Jul (Test I and II, respectively) all plants in the buffer rows were cut off at 3 to 4 leaves above the ground. Suckers grew from the axils of the remaining leaves and on 23 Jul and 8 Aug all but 1 healthy sucker were removed. Due to the presence of a naturally occurring budworm population, plants containing a single early instar budworm were selected and tagged on 4 and 19 Aug (Test I and II, respectively). Variable numbers of plants were tagged in each plot. Treatments were applied on 5 and 20 Aug (Test I and II, respectively) as previously described. Three and 10 days post-treatment the number of surviving larvae were counted and the proportion of surviving calculated. Damage ratings (0 to 4 scale) were made after 14 days. Prior to ANOVA, count data were transformed to and proportions were transformed to arsin .