This season we had a very wet June was followed by a dry July, August and most of the month of September. These conditions led to the build up of leaf feeding (phytophagous) mite on fruit and ornamental trees. Along orchard roads dust kicked up by vehicles causes mite to increase egg laying, leading to higher populations while a lack of rain allowed young mite to grow unhampered by heavy rain that might otherwise dislodge and reduce the nymph and young motile stages of mite presence on the tree.
Mite buildup late this season may at least, in part, be due to the need for additional management for the stink bug complex including the migration of the brown marmorated stink bug into Hudson Valley orchards during the dry weeks of the season. Two Spotted Spider Mite in very high numbers and injury to foliage was noted in mid-September in late strains of Fuji.
The two spotted spider mite, Tranychus urticae, (TSSM) are indirect pests of apple and cyclical from year to year. They feed by extracting leaf sap from cells that reduce photosynthesis and carbohydrate production of the tree.
A lower threshold for TSSM then that used for European red mite would be employed seasonally to reduce the chance of a severe infestation that gives rise to leaf bronzing, reduced photosynthesis, fruit size reduction, preharvest drop, poor fruit coloring, and reduced fruit bud development and subsequent crop potential for the following year.
The adult female TSSM mite’s summer color pattern varies, but most are greenish yellow with a prominent dark spot on each side near the middle of the body. These spots often enlarge to cover most of each side of the body as the mite feeds. The body is somewhat egg shaped and broadest toward the head region.
The twospotted spider mite passes through two developmental stages. The eggs are spherically shaped and shiny; their color varies from light or clear to pale green and are most often translucent. Larva hatch after two to three days, have four legs Nymphs pass through .
Twospotted spider mites overwinter as orange-colored females. In orchards, the overwintering females congregate under debris on the orchard floor or bark scales at the base of trees. During the spring the twospotted spider mite feeds on vegetation, especially vetch and other legumes underneath the trees.
As these orchard floor hosts dry out with the arrival of hot weather, twospotted spider mites move into trees. Hot, dry weather is favorable to population increases of this mite. Mite management emphasizes orchard floor management, scouting of pest and beneficial populations, and consideration of other stresses on the trees.
Management of the overwintering phase is not recommended.
And as Rick Weires (HVRL Entomologist 1974-1990) would state under these situations (paraphrased)…’it might help you sleep better but in the end, would only be an act of ‘Revenge Spraying’ with very little benefit.