• dust;
  • mite outbreaks;
  • stress


The effect of dust on phytophagous mite numbers was examined in five apple orchards situated in the dry, inland apple producing Ceres area, South Africa. The study was conducted over three seasons. The season with the most dust had the least number of mites. There was no relationship between the amount of dust on leaves and mite numbers from different orchards. Of the 15 correlations between the amount of dust on individual trees and the number of mites on these trees, two were marginally not significant and one was highly significant, but negative. Therefore, seasons during which there is a lot of dust did not result in mite outbreaks nor did dusty orchards harbour elevated mite population levels, and trees with a lot of dust did not necessarily harbour more mites than trees with less dust. However, if there is enough dust to cause stress to the trees, phytophagous mite outbreaks could occur.