ARS | Publication request: EVALUATION OF GRANULAR BIOINSECTICIDES UNDER FIELD CONDITIONS

Submitted to: Mexican Association of Microbiology and National Congress Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: April 6, 1995
Publication Date: N/A

Technical Abstract: The purpose of this study was to optimize the bioinsecticidal activity of Bacillus thuringiensis (Bt) and to augment its residual activity by using different strains and formulations. The specific objectives focused on 7 strains within 4 serotypes of Bt; granular formulations based on matrix forming materials for sustained release; and cultivation conditions within a 14-liter fermenter. To find the insecticidal and residual activity, formulations were applied for the control of lepidopterous pests of corn in the field. Fermentation media for Bt was: molasses (20 ml/L), soy flour (20 g/L), liquid corn steep (10 g/L), CaCO2 (1 g/L), pH 7.0. Fermentation was carried out for 30 hr. Formulations were based on those described by Castro-Franco (1994) with two doses of Bt; 2% and 4% wt/wt. The field plot was located in the region of Bermejillo, Durango and set up in a randomized complete block with four repetitions. Treatments consisted of chemical and biological control agents and controls. Significant differences occurred in the number of Lepidoptera (Heliothis, Trichoplusia, and Spodoptera) after the first application (a total of 3 applications were made) with chemical insecticides providing the best control. Following the second and third applications, chemicals were similar in effectiveness to biologicals. However, 3 strains of Bt from the serovars aizawai, gallierie and kurstaki were significantly better than chemicals and the other strains of Bt. The best control occurred with formulations containing 4% Bt. These results suggest the possibility of using strains of Bt in granular formulations for the control of Lepidoptera in corn.