|Tamez-Guerra, Patricia - UNIV AUTO, MONTERREY,MEX|
|Medrano-Roldan, H - INST TECHN, DURANGO,MEX|
|Gala-Wong, L - UNIV AUTO, MONTERREY,MEX|
Submitted to: Entomology International Congress
Publication Type: Abstract Only
Publication Acceptance Date: August 31, 1996
Publication Date: N/A
Technical Abstract: Formulations incorporating modified starches and flours were developed for extending the residual activity of Bacillus thuringiensis (Bt). The basic formulation contained nixtamalized flour (commonly used in Mexico for tortillas), cornstarch, corn oil, lactic acid, alcohol, and sugar. When mixed with water and active ingredient and spray dried, small granules were formed. These granules could then be added to a spray tank and sprayed onto a target. Variations of these ingredients included substituting the nixtamalized flour with pregelatinized flours or starches commonly available in the U.S. Tests were conducted in the laboratory to determine insecticidal activity of Bt and resistance to simulated environmental factors. In diet incorporation tests against three insect species, formulated Bt killed as many or more larvae than unformulated Bt suggesting that the ingredients and processing did not harm the activity. In many cases, activity was increased perhaps due to the feeding stimulant property of the formulation. Cotton leaf surfaces were treated with the formulations and exposed to full simulated sunlight delivered by a Suntest CPS (Heraeus) for 8 h. Unformulated Bt routinely lost about 50% activity during this exposure; however, Bt formulated in nixtamalized flour retained 90-95% activity. There was a reduction of solar stability as the amount of Bt increased in the formulation. We believe these formulations offer a viable, microencapsulated system utilizing surplus, natural materials.