ABSTRACT
The successful substitution of the classical poisonous substances by microbial insecticides is a very significant enhancement in the protection of forest plants against insect pests. Good results have been achieved by the application of biological preparations based on the bacterium Bacillus thuringiensis ssp. kurstaki and baculoviruses. Starting from the fact that the microbial insecticides are of the highest quality, attention should be directed to the following factors: population level of the target insect, the degree of foliage expansion and larval instars, forest stand structure, meteorological conditions, sunlight, orographic characteristics and technology of application.
