Modification of host finding and oviposition behaviour of the citrus leafminer, Phyllocnistis citrella, by horticultural mineral oil

Horticultural mineral oil (HMO) deposits affect postlanding searching behaviour and contact evaluation of oviposition substrates by females of the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae). Both unsprayed and sprayed lemon trees were equally capable of arresting randomly moving female moths by eliciting kinetic responses. The presence of HMO deposits did not affect the approach of female moths to flushes (shoots with immature leaves suitable as oviposition sites), and female moths were equally likely to land on sprayed and unsprayed immature flushes provided mature leaves were not sprayed. The presence of HMO on both the mature leaves and the flushes caused shorter residence and search times within trees and also resulted in fewer immature leaves visited. The HMO-sprayed flushes were also more likely to be rejected for oviposition after contact. Nevertheless, eggs were sometimes deposited on sprayed flushes between residues of the oil droplets.