LABORATORY EVALUATION OF MINERAL-OILS FOR CONTROL OF CODLING MOTH (LEPIDOPTERA, TORTRICIDAE)

Horticultural mineral oils are ovicides against the codling moth, Cydia pomonella (L.), when applied directly to the eggs. The susceptibility of eggs to the oil varied depending on the substrate on which eggs were laid. On an inert surface such as waxed paper, young eggs were three times as susceptible as eggs laid on apples. Susceptibility to oil changed little throughout the incubation period except just before hatch when egg susceptibility dropped markedly. There was no difference in ovicidal activity among three commercial horticultural mineral oils. Eggs laid on top of oil residue were not affected at labeled rates. Topical treatment of neonates caused no mortality at concentrations equivalent to field rates. Oil residue on the fruit surface did not inhibit neonates from entering fruit tissue. Moths suffered no mortality from direct oil treatments. Although the total number of eggs deposited by oil-treated and untreated moths was the same (107.5 and 90.3 eggs per female, respectively), treated moths discharged their egg supply at a faster rate. Female moths avoided fruit surface with oil residue for oviposition. Results suggest that dilute applications of 1% horticultural mineral oil may not be adequate for reducing codling moth egg hatch in the field.