EGG DISPERSION IN CODLING MOTH - INFLUENCE OF EGG EXTRACT AND OF ITS FATTY-ACID CONSTITUENTS

Codling moth females (Cydia pomonella, Lepidoptera: Tortricidae) (CM) usually lay single eggs and have a tendency to disperse. In a first ex periment we observed that single females exposed to 20 apples distribu te their eggs regularly among apples, suggesting a dispersive oviposit ion behavior. In a dual-choice situation, isolated females avoided ovi position on areas of cardboard treated with a methylene dichloride egg extract at the dose of ca. 1.0 egg equivalent/cm(2). A strong avoidan ce was obtained in response to a 20-fold dose, which was accompanied b y a significant reduction of total oviposition. Seven major compounds found by GC analyses in the methylene dichloride extract of 2 to 3-day -old eggs were saturated or unsaturated C-14-C-18 straight-chain fatty acids: myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid. This was confirmed by G C-MS analysis of an extract made by ethyl ether. Smaller amounts of th ree methyl esters were also identified as methyl myristate, methyl pal mitate, and methyl stearate. A blend of the seven fatty acids (FA) mim icked rather well the avoidance provoked by the extract, and this avoi dance was confirmed by choice between treated and untreated fruits by single females. The treatment of apples with the 7FA mixture induced a n aggregative distribution of the eggs among apples. We also found tha t the amounts of fatty acids harvested in the extract depend on the eg g age. Amounts of fatty acids increased until eggs were 4 days old and then decreased before hatching. In this paper we discuss the possible role of simple molecules, such as fatty acids and their esters, as se miochemicals indicative of juvenile tissues.