SEASONAL DENSITY AND IMPACT OF MINING OF LYONETIA-PRUNIFOLIELLA (LEPIDOPTERA, LYONETIIDAE) ON SEMIDWARF APPLE-TREES IN CONNECTICUT

Number of adults on unbaited yellow sticky traps and of new mines and pupae on semidwarf 'McIntosh' or 'Mutsu' apple, Malus domestica Borkha usen, trees was recorded weekly at Southington, CT, to determine the s easonal density of Lyonetia prunifoliella (Hubner) in 1989 and 1990. D ensities were highest between August and October when leaves of the se cond flush were developing. On sprayed 'Mutsu' trees, L. prunifoliella had at least six generations between May and November 1989, and four during these months in 1990. An application of permethrin in April pro bably eliminated the first generation in 1990. On 'Mutsu' apple trees, the loss of leaves of the second flush in 1990 was significantly grea ter on terminal shoots with mining than on those without it. Foliar mi ning also significantly reduced the length and basal diameter of termi nal shoots. By reducing woody growth on young trees, the premature los s of leaves may delay the first harvest. Pruning in summer and fewer a pplications of fertilizer might slow the population growth of L. pruni foliella.