SPRAYABLE GRANULE FORMULATIONS FOR BACILLUS-THURINGIENSIS

Spray-dried Bacillus thuringiensis subsp. kurstaki formulations, compo sed of citric or lactic acid, pregelatinized corn flour, cornstarch, i sopropyl alcohol, sugar, and corn oil, were used in leaf and diet inco rporation bioassays to determine the effects of solar radiation and ra in on insecticidal activity. In diet incorporation tests against Helic overpa zea (Boddie), Trichoplusia ni (Hubner), Heliothis virescens (F. ), and Spodoptera exigua (Cramer), insecticidal activity of spray-drie d B. thuringiensis did not decrease when compared with unformulated te chnical B. thuringiensis. Cotton leaf bioassay tests using Ostrinia nu bilalis (Hubner) showed that insecticidal activity of formulations exp osed to 8 h of artificial solar radiation was significantly higher tha n technical B. thuringiensis exposed to solar radiation, suggesting th at the formulations provided protection against solar radiation. In co tton leaf bioassays, when 5 different starches were used individually in the formulations, insecticidal activity was significantly reduced i n only 1 case after exposure to solar radiation. Cotton leaf bioassays also showed a reduction in insecticidal activity caused by exposure t o solar radiation as the amount of active ingredient (wt:wt) in the fo rmulation increased. Throughout all tests, rainfastness of formulation s was not consistently better than technical B. thuringiensis alone.