"Russet mites are so small that a 14X hand lens is needed to see them. Because of their size, these mites are rarely noticed until plants are damaged. By this time, there may be hundreds of yellowish, conical-shaped mites on the green leaves immediately above the damaged bronzed leaves. (E. T. Natwick, et. al., 2014) University of California Statewide IPM Program
Russet mites are most abundant during hot, dry weather in the mid- and late summer. The russet mite has a high reproductive potential (up to 53 eggs per female) and can complete a life cycle (egg to adult) in a week at warm temperatures. Females live for about 22 days laying eggs on the undersides of leaves, leaf petioles, and stems. Young nymphs tend to feed close to where they hatch. Mite feeding is usually concentrated on the lower part of the plant, but when infestations are severe and plants become heavily damaged, mites will disperse to upper leaves. The females over winter inside plant stems, where branches join main plants, and sometimes in root structures. Indoor populations can remain on plants year round. The mites move towards the top of dying plants and can crawl between closely spaced plants that are touching, and can be carried by the wind or splashing water.
Recommended controls for russet mites
Each control will have its own set of parameters that will be best suited for individual environments. Certain controls may only be available for commercial application.
Commercial farmers are required to reference their own state laws to ascertain if the recommended controls fall within compliance of their states regulatory guidelines.
MECHANICAL AND PHYSICAL CONTROLS
Mite Treatment: Heat Treatments
Russet, Cyclamen or Broad mites are very sensitive to heat. They are more difficult to control in winter than in summer due to lower greenhouse temperatures.
Hot Water Treatment: Soaking infested plants in water held at 111 - 115 degrees F for 15 minutes will destroy these mites without damage to most plants. (Not recommended for Medical or Hemp growers: use Hot Air Treatment)
Hot Air Treatment: This method can only be used in contained areas (areas or rooms that can be sealed) by raising the air temperature to 115 degrees F for 15 to 20 minutes. Best results were reported with 100% humidity using (at least) two circulation fans to create some vortex1. As all eggs may not be terminated using this method, weekly repeat applications may be necessary to achieve desired results.
Note 1: Fans are usually NOT necessary for small tents, closets, etc. (if installed, use the return air system for re-circulation). NEVER place fans so they are blowing directly on your plants; they will dehydrate.
Note 2: for Cannabis Growers: efficacy of heat treatment is directly proportional to your canopy density: as canopy density increases, heat treatments will become less effective as pest insects will simply retreat into new node formations. Heat treatments are most effective while in veg cycle.