Microencapsulation and PBO: a tool in resistance management of the green peach aphid

Insecticide resistance can be a serious threat to the application of Integrated Pest Management. The Green Peach-Potato Aphid, Myzus persicae (Sulzer) is a serious pest in peach orchard. Insecticide treatments have selected many populations that have different degrees of insecticide resistance due to different resistance mechanisms. These resistance mechanisms can interfere with many classical insecticide classes, but, fortunately, till now, there is no clear evidence for resistance to neonicotinoids. The severity of this problem is also increased by the reduction of the available active ingredients that can lead to an abuse of a single group of insecticides. Many populations of M. persicae, both in Italy and in Europe, over-express a carboxylesterase (E4/FE4) that reduces in various degrees the efficacy of several insecticides by hydrolysis and/or by sequestering. Recently, many authors have demonstrated that piperonylbutoxide (PBO) can efficiently interfere with esterase activity overcoming insecticide resistance. Several microencapsulated products (in polyurea or cyclodextrin) with PBO and various active ingredients have been tested in laboratory bioassays against a susceptible and against an esterase resistant population of M. persicae. A comparison was done with the commercial formulated products alone or mixed with PBO. The results achieved with the different formulation are discussed in term of increased mortality, application rate as well as offsprings reduction. According to the results, the use of these types of microencapsulation together with PBO could be an interesting tool to be included in resistance management strategies against the green peachpotato aphid.