Assessment of a Counting Method Combining Brushing and Printing Procedures to Estimate the Density of Spider Mites on Apple Trees

摘要

The efficacy of brushing and printing procedures was investigated to assess a counting method combined with brushing and printing procedures to estimate mite density on apple trees. Using leaf samples from apple orchards, digitized dots obtained from the printing procedure were chosen for counting and investigated by regression analysis of mite density. When mite density was an adult female per leaf, 87% of mites were dropped onto paper. When mite density was 10 adult female per leaf, 55% were dropped. Printing efficacy was high when mite density was low, and adversely, it was low when density was high. This trend explains the results of samples from the apple orchard; however, the number of dots chosen using the digitalized process correlated well with mite density when the density was lower than 8 females per leaf. Therefore, mite density could be estimated by the regression equation: y=0.68x+1.55, with 0.89 of the coefficient when the dots were chosen at 75 dpi of digitized resolution and 170 binary threshold.