Control of Tobacco Insect Pests with Bacillus Thuringiensis Var. Kurstaki and Thuringiensin Formulations, 1986
Authors: Michael Jackson D. 
Published: March 2022

Several formulations of Bacillus thuringiensis var. kurstaki (B.t.k.) and Thuringiensin (|3-exotoxin), a secondary metabolite of certain B.t. strains, were tested for control of tobacco budworm and tobacco hornworm larvae on ‘Speight G-28’ flue-cured tobacco at Oxford, NC. These materials were: Dipel 2X (wettable powder; 32.0 billion international units (BIU)/kg), Dipel 4L (emulsifiable suspension; 8.5 BlU/liter), Dipel 10G (granular; 1.6 BlU/kg), ABG-6158 (emulsifiable suspension; Dipel 8ES; 16.9 BlU/liter), ABG-6167 (aqueous flowable; Dipel 8AF; 16.9 BlU/liter), ABG-6181 (granular; Dipel 14G; 2.24 BIU/ kg), ABG-6200 (granular; Thuringiensin-G; 0.3% w/w Thuringiensin), ABG-6206 (wettable powder; Thuringiensin Calcium, 10% w/w), Bactospeine FC (flowable concentrate; 9.3 BlU/liter), Bactospeine WP (wettable powder; 16.0 BlU/kg), Bactospeine G 12/14 (granular; 2.8 BlU/kg; 12/14 mesh carrier), and Bactospeine G 14/40 (granular; 2.8 BlU/kg; 14/40 mesh carrier). Orthene Tobacco Insect Spray (TIS)(75SP) was used as an insecticide check. Tobacco was transplanted on 19 and 27 May into a field of Helena sandy loam which had been treated with isopropalin (Paarlan, 1.68 kg Al/ha) and metalaxyl (Ridomil 2E, 0.56 kg Al/ha) for weed and disease control. Diphenamid (Enide 90W, 4.48 kg Al/ha) was applied on 16 Jun for additional weed control. Plants were placed on 55.9-cm centers with 1.22 m between rows. Single row plots of 30 plants (experiments 1-4) or 20 plants (experiments 5 and 6) were set up in randomized complete block designs with 4 (experiment 4) or 5 (Experiments 1-3, 5, and 6) replicates. On 24 Jul, plants in one half of the field were cut off ca. 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 2 to 3-day-old tobacco budworm larvae (Experiments 1, 2, 5, and 6) or two 3-4-day-old tobacco hornworm larvae (experiments 3 and 4) from laboratory colonies on 25 Jun, and 1, 15, 22 Jul, and 11 and 12 Aug for experiments 1-6, respectively. Seldom does more than one budworm larvae survive per plant in the untreated controls. A new tobacco budworm laboratory colony is started yearly from larvae collected from tobacco in the late summer. The tobacco hornworm colony has been in continuous culture for 21 years. Plots were treated on 27 Jun, 3, 17, 24 Jul, and 14 and 15 Aug. Spray applications were made by a CO2-powered backpack sprayer with an adjustable nozzle at a rate of 233.8 l/ha with 4.1 × 105 Pa. Granular materials were measured into individual 30-ml cups for each plant, then sprinkled by hand from a height of 15-30 cm over each tobacco bud. There were no buffer rows between plots, but spraying was done in the early mornings when winds were negligible. An additional set of unsprayed check plots were set up for the hornworm experiments (3 and 4) in a remote field to help identify drift problems between plots. No drift problems were encountered in either experiment. Live larvae were counted 3 or 4 days after spraying for all experiments. Live larvae were also counted on day 7 for experiment 1, and damage ratings (0-7) were made on day 7 for experiment 2. All data were transformed to Vx + 0.5 before analysis of variance, but data are presented in the tables as untransformed means. Means were separated using Waller-Duncan k-ratio t-test; k = 100, a = 0.05.