Control of Tobacco Insect Pests, 1988

Several formulations of Bacillus thuringiensis var. kurstaki, thuringiensin ((β-exotoxin, ABG-6162A) and fenoxycarb (ABG-6231), were tested for field control of tobacco budworm and tobacco hornworm larvae on ‘Coker 176’ tobacco at Oxford, N.C. Six separate experiments were run. Orthene Tobacco Insect Spray (TIS) (75% soluble powder) was used as an insecticide standard. Tobacco was transplanted 10 May into 3 fields that had been treated with isopropalin (Paarlan, 1.68 kg [AI]/ha) and metalaxyl (Ridomil 2 EC, 0.56 kg [AI]/ha) for weed and disease control. Diphenamid (Enide 90 W, 4.48 kg [AI]/ha) was applied after transplanting (28 Jun) for additional weed control. Plants were placed on 55.9-cm centers with 1.22 m between rows. Single-row plots of 15 plants each were set up in randomized complete block designs with 5 replicates for each experiment. On 5 Jul, plants were cut off 10 cm above the ground. One sucker was allowed to regrow from each plant, and this regrowth was used in Experiments 5 and 6. Plants were infested with two 3-d-old tobacco budworm larvae (Experiments 1, 2, 4, and 5) or two 4-d-old tobacco hornworm larvae (Experiments 3 and 6) from laboratory colonies on 10, 24, 21, and 20 Jun, 29 Jul, and 3 Aug for Experiments 1-6, respectively. Plots were treated on 13, 27, 23, and 24 Jun, and 1 and 5 Aug. Spray applications were made by a CO2-powered backpack sprayer with an adjustable nozzle at a rate of 233.8 liters/ha with 4.1 X 105 pascals. Live larvae were counted 3 or 4 DAT. Plots in Experiments 1 and 2 were also checked at 7 DAT.