Abstract: Helicoverpa armigera (Lepidoptera: Heliothinae) is an insect pest, which severely harms vegetables, cotton and flowers. A good solution for controlling H. armigera and other lepidopteran larvae, especially in organic farms, is a treatment with Bacillus thuringiensis (Bt). The problem of spraying with Bt is its sensitivity to UV light emanating from the sun, making the spray preparation short lived. The laboratories of BotanoCap (Israel) have developed a formulation, which is more stable to UV radiation and might be active for a longer period of time, compared with the regular preparation. In our experiments we compared the efficacy of BotanoCap’s encapsulated B.t. var kurstaki formulation, which is considered to be UV-resistant, to a non-encapsulated standard preparation. Both formulations were tested with and without exposure to sunlight.Exposure to sunlight of the encapsulated formulation did not cause a reduction in mortality of H. armigera larvae (3rd instars) in comparison with the standard (non-encapsulated) preparation. The non-encapsulated formulation lost most of its efficacy after exposure for about four hours to sunlight. It is advisable to repeat the experiments in the field, with direct spraying on the crop plants.