Side-effect testing of novel powdery mildew fungicides against biological control agents

Abstract: There is increasing interest in using alternative fungicides, such as inorganic salts andplant extracts, including those from giant knotweed (Reynoutria sachalinensis), to controlpowdery mildew on protected herbs. However, it is important that these alternative fungicides arecompatible with biological pest control, which is used in Integrated Pest Management (IPM)programmes by growers of protected herb crops.This study tested mortality effects of a range of inorganic salts and an extract of giantknotweed on two biological control agents, Aphidius colemani and Neoseiulus cucumeris, whichare used to control aphids and thrips on protected herb crops. The bioassays completed usedworst case (Tier 1) scenarios where the biological control agent was either dipped or exposed toleaves sprayed with the fungicide.Based on the IOBC classification of plant protection products for their side-effects onbeneficial arthropods the inorganic salts and extract from giant knotweed were ‘non-toxic’against N. cucumeris and A. colemani adults. Although the side-effects of these potentialalternative controls for powdery mildew should be tested against the full range of biologicalcontrol agents used in IPM programmes on protected herbs, these results indicate that they shouldbe IPM compatible.