Conservation of natural enemy fauna in citrus canopies by horticultural mineral oil: Comparison with effects of carbaryl and methidathion treatments for control of armored scales

Abstract

The disruptive effects of an nC24 horticultural mineral oil (HMO) and two other insecticides (carbaryl and methidathion) on two armored scale insects and natural enemy fauna were evaluated in two citrus orchards. In the first orchard, all three spray treatments and non-sprayed controls were distributed separately among individual trees in one block, whereas in the second orchard the control, HMO and methidathion treatments were applied at the level of whole blocks. The results in both orchards were similar. All three of the spray treatments had a lethal effect on the red scale insects and the effects of HMO and methidathion tested at the second site lasted for at least 19 weeks and for purple scale, at least 50 weeks. HMO did not have a significant effect on the abundance and species diversity of parasitoids and (for the most part) did not affect coccinellids and predatory mites. Both carbaryl and methidathion caused significant ongoing disruption to the above groups. No treatment resulted in the resurgence of the scale insects or the outbreak of phytophagous mites, even where whole blocks were sprayed. © 2010 The Authors Journal compilation © Institute of Zoology, Chinese Academy of Sciences.