Ecofriendly synergists for insecticide formulations (EcoSyn): in vivo evaluation of novel synergists against resistant pests

In the framework of EcoSyn project, after synthesis and in vitro evaluation of different novel compounds, a list of possible novel synergists was selected on the basis of the highest inhibition rate obtained in vitro assay against purified esterases and recombinant P450 enzymes. Also difficulties and cost of chemical synthesis were considered. The well known synergist piperonyl-butoxide (PBO) was included in the list to be used as a standard reference. Laboratory bioassays were performed combining these compounds with commercial formulated insecticides (2 pyrethroids and 2 neonicotinoids) against lab reared resistant Myzus persicae and Bemisia tabaci populations. All these populations were collected in the previous years in Northern Italy after serious field control failures after neonicotinoid and / or pyrethroid applications. Efficacy against Italian and Polish populations of Pollen Beetle (Meligethes aeneus) was also evaluated. In this case field collected insects were used as no lab rearing protocols are currently available for this pest. As in Italy oil seed rape is not a common crop and above all it is not usually treated with insecticides, Italian populations of M. aeneus were considered as susceptible reference to be compared with more resistant Polish populations. Different performances have been observed for the various combinations of pest / synergist / insecticide / application rate / type of bioassay. In almost every case the mortality achieved applying the insecticide plus the synergist was significantly higher than the mortality produced by the insecticide alone. When used alone the synergists gave low mortality level usually not different from the level observed in the corresponding untreated control. In several cases performance improvements, in comparison with PBO, have been recorded and highest synergistic ratio were measured.