Sampling Mites on Peach Leaves with the Henderson-McBurnie Machine1

Abstract

The mite-brushing machine of Henderson and McBurnie (1943) greatly facilitates the sampling of populations of phytophagous mites. Morgan et al. (1955) found that mites on apple leaves could be sampled more accurately by its use than by direct microscopic examination on the leaves. However, 12 years’ experience with this machine at Vineland Station has shown the need of special precautions to remove eggs of the European red mite, panonychus ulmi (Koch), from peach leaves, owing to the complex curvature of these leaves. Lengthwise, a typical peach leaf curves downward, and transversely the lamina curves upward and outward in an are from each side of the midrib. The upper side of the midrib is depressed below the level of the lamina, and on the under surface there are grooves along each side of the midrib where the lamina joins it. Mite eggs are largely concentrated in these protected areas along the midrib on both upper and lower surfaces of the leaf. The paper-impression method of sampling mites (Venables and Dennys 1941) cannot be used with peach leaves because their curvature causes the lamina to be thrown into folds when they are pressed onto a plane surface.