Seasonal Density and Impact of Mining of Lyonetia prunifoliella (Lepidoptera: Lyonetiidae) on Semidwarf Apple Trees in Connecticut

Abstract

Number of adults on unbaited yellow sticky traps and of new mines and pupae on semidwarf ‘Mcintosh’ or ‘Mutsu’ apple, Malus domestica Borkhausen, trees was recorded weekly at Southington, CT, to determine the seasonal density of Lyonetia prunifoliella (Hübner) in 1989 and 1990. Densities were highest between August and October when leaves of the second 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 probably eliminated the first generation in 1990. On ‘Mutsu’ apple trees, the loss of leaves of the second flush in 1990 was significantly greater on terminal shoots with mining than on those without it. Foliar mining also significantly reduced the length and basal diameter of terminal shoots. By reducing woody growth on young trees, the premature loss of leaves may delay the first harvest. Pruning in summer and fewer applications of fertilizer might slow the population growth of L. prunifoliella.