Influence of petroleum‐derived spray oil aromaticity, equivalent <i>n</i>‐paraffin carbon number and emulsifier concentration on oviposition by citrus leafminer, <i>Phyllocnistis citrella</i> Stainton (Lepidoptera: Gracillariidae)

Abstract Two experiments showed that the effect of petroleum‐derived spray oil residues on oviposition by citrus leafminer is related to the number of carbon atoms in oil molecules but not to aromaticity and emulsifier concentrations. An n C25 medicinal‐oil fraction was more effective than n C17 and n C22 fractions. Efficacy of petroleum‐derived spray oils used as oviposition deterrents to control citrus leafminer is therefore related to timing of spray application, the amount of oil deposited on sprayed surfaces (dose) and the persistence of oil molecules on sprayed surfaces.