Spatial Dynamics and Sampling of Lyonetia speculella (Lepidoptera: Lyonetiidae), a Leafminer of Apple

Abstract

The abundance of Lyonetia speculella Clemens larvae on each tree of a 1.25- ha apple orchard, planted in 1986, was determined monthly from June to September 1986 and May to September 1987. In both years, the abundance of L. speculella was low initially, increased in early summer, remained constant through midsummer, and increased again at the end of the summer. L. speculella abundance per tree was aggregated, but the distribution of infested trees was initially random, then regular for the remainder of each year. The initial increase in abundance was caused by an increase in the percentage of the trees infested and the late summer increase by an increase in aggregation on infested trees. There were differences in distribution of mines between ‘Northern Spy’ and ‘Red Delicious’ because of phenological and growth habit differences between the two cultivars. An application of oxamyl in 1986 temporarily altered the spatial distribution of L. speculella , increasing the aggregation and decreasing the percentage of the trees infested for the sample following oxamyl application. A graph of the relationship between sample size and sampling precision is provided to estimate required sample size for future studies. Random, systematic, random cluster, and systematic cluster sampling designs were all equally effective in simulated sampling from the field data