Control of Tobacco Budworms and Tomato Hornworms with Bacillus Thuringiensis Var. Kurstaki, 1981

Two isolates of Bacillus thuringiensis var. kurstaki was tested against artificial infestations of tobacco budworms and natural infestations of tomato hornworms at Oxford, NC, in 2 separate tests. Tobacco was transplanted on May 18, in a sandy loam field that had previously been treated with Telone C-17 (10.5 gal/acre), Paarlan 2 pt/acre), and Ridomil 2E (2 pt/acre). Fertilizer (8-8-24) was applied at 500 lb/acre on May 27, and plants were sidedressed with 15-0-15 (100% nitrate) fertilizer at 167 lb/acre on Jun 8. Rows were 4 ft apart, and plants were spaced 22 in. Plants in Test 1 were artificially infested near the bud with one 1-day-old tobacco budworm larva/plant on Jun 12. Larvae were from an Oxford laboratory colony that had been started from field collections and cultured for ca 10 generations. Pior to release, larvae were fed on an artificial diet. On Jun 15, plants were examined for successful budworm establishments, and 40 plots of 20 infested plants each were marked in a randomized complete block design with 5 blocks. Plots were treated on Jun 16. Sprays were applied with a CO2-powered backpack sprayer with an adjustable nozzle at a rate of 25 gal/acre with 60 psi. Measured amounts of baits were placed by hand into the tobacco buds. Plants were examined for insects 3, 7, and 10 days after spraying, and on day 10 they were subjectively rated from 0-7 for budworm damage. One week after Test 1, all plants were cut off near the ground and removed from the field. One sucker was allowed to grow per plant, and this new growth was used for Test 2. Plants were infested with budworms on Jul 27, and 45 plots of 15 plants each were marked off in a randomized complete block design with 5 blocks on Jul 30. Treatments were made on Jul 31, and plants were checked 3 to 6 days later.