The aim of the work was to estimate the insecticidal activity of Bacillus thuringiensis MPU B9 spore-free preparation of crystals against Leucoma salicis caterpillars (willow and poplar pest). The results revealed a high biological activity of B. thuringiensis MPU B9 crystals towards L. salicis larvae. This may be caused by production of numerous, different crystalline proteins by the MPU B9 isolate. The high value of insecticidal activity make this strain a promising candidate for future research on a new efficient preparation against plant pests.