Use of Bacillus thuringiensis var. kurstaki formulations for the control of harmful defoliators in the order Lepidoptera.

During my studies in forest trees protection from insect pests, my attention has focused on the use of Bacillus thuringiensis var. kurstaki formulations for the control of harmful defoliators in the order Lepidoptera. My activity has been oriented particularly on the protection of pine forests from Pine Processionary Caterpillar infestations. To this regard various field and laboratory experiments on the use of Btk formulations were carried out, employing different doses against I and II instar larvae and also against IV and V instar larvae. The results of these tests showed high efficacy of the Btk products against early instar larvae, independently of the dose employed. On the contrary the same products, employed at higher doses against IV and V instar larvae, always caused similar or slightly higher larval mortality to that recorded in the field. The same trials were repeated, in the same periods, also in confined environment and their results confirmed those obtained in the field. In the laboratory the survival of the spores and the efficacy in time after the treatment of different Btk formulations were investigated. The Pine Processionary Caterpillar is one of the most important phytophagous insects for the ecological and selvicultural damages caused to the pine forests and it is also one of the most feared species in urbanized environments because of the urticant hairs of larvae starting from the III instar and their effects on humans and other homeothermic animals. For these reasons it is my intention to carry on with the experiments on the use of Btk preparations mainly on III and IV instar larvae in the winter, when the nests are easily recognizable and nontarget species are no longer active. Since this approach has minimal impact on the natural environment, it would be recommended for use in areas where a certain amount of damage is tolerated. On the contrary its use in an urban environment, where the treatment threshold is very low because of the socio-sanitary problems connected with the urticant hairs, is still not sufficiently evaluated.