Hemp Russet Mite, Aculops cannibicola

Order: Acari
Family: Eriophyidae

Description

Hemp russet mites are very small and have cylindrical bodies that taper sharply at the rear. These mites cannot be seen without a lens capable of at least 15-20x magnification. They are pale and have two pairs of legs near the head, unlike most mites which have four pairs of legs. They feed on the surface of leaves by piercing plant cells and extracting cell contents. Hemp russet mites do not produce webbing, which distinguishes them from many other pestiferous mites.

 

Quick Facts

  • Hemp russet mites belong to the family Eriophyidae. The eriophyid mites are a group of arthropods that feed on plants and cause deformities. There are currently 1,859 species documented worldwide.
  • Hemp russet mite is highly host specific and only feeds on cannabis and hemp plants. They can significantly reduce yields when densities are high.
  • Hemp russet mite is one of the most injurious arthropods in industrial hemp.
Hemp russet mites on hemp

Hemp russet mites on a hemp leaf. Several mites can be seen hanging from the leaf edge, a behavior that allows these mites to become wind-borne.
Whitney Cranshaw, Colorado State University, Bugwood.org

Hemp russet mites are eriophyid mites, which include 1,859 species worldwide. These mites cannot be seen with the naked eye; however, certain plant deformities indicate that an infestation may be present. This pest can significantly reduce hemp yields if left untreated.

Unhealthy and healthy hemp leaves

Two hemp leaves, one leaf heavily damaged by feeding of hemp russet mite (left) and a healthy leaf (right).
Whitney Cranshaw, Colorado State University, Bugwood.org

Hemp plant with feeding injury

Hemp plant showing signs of feeding injury from hemp russet mite. Note the distorting of the bud and new leaves.
Whitney Cranshaw, Colorado State University, Bugwood.org

Life History and Habits

The biology of hemp russet mite is not well understood. Hemp russet mite can crawl short distances and disperse by using wind currents. The mites overwinter in crop debris but can survive indoors with a consistent food supply. Hemp russet mites tend to prefer the underside of leaves, but as densities increase, they will spread to other parts of the plant such as the upper side of leaves, stem, and flower buds.

The entire life cycle of hemp russet mite can be completed in as little as one week under favorable environmental conditions, especially high relative humidity and temperature. Hemp russet mites produce multiple overlapping generations each year.

Injury

Feeding injury will not be noticeable when mite densities are low, and some symptoms like leaf curling will not be present on all plants. High densities of hemp russet mite will cause reductions in leaf size, brittle foliage, and a bronze or rusty appearance of leaves and stems. Plants with severe infestations will also have abundant exuviae (cast skins), which may appear as a dark powder-like substance on leaves and stems. If an infestation is left untreated, feeding of hemp russet mite can reduce yield and cannabinoid quality.

Cultural Control

When cloning, carefully inspect clippings and the parent plant to verify that hemp russet mite is absent, or densities are low. Any tools used to work with infested plants should be cleaned before use on healthy plants. Within the field, plants infested with hemp russet mite should be removed and destroyed. Lastly, the spread of hemp russet mite can be restricted by limiting the movement of people and supplies between infested and uninfested areas.

Established infestations are extremely difficult to eradicate in growing areas with continuous production systems. In these cases, plants should be removed from the infested area. In the absence of host plants, the remaining mites will die within a month.

Biological Control

One species of predatory mite, Amblysieus andersoni, is known to feed on hemp russet mites. Two predatory mites, Phytoseiulus persimilis and Amblysieus californicus, are used in twospotted spider mite management but are not effective against hemp russet mites.

Chemical Control

There are several horticultural oils that can be applied as dips or foliar sprays to kill mites. For more information on chemical management of hemp russet mite, consult the Colorado State University management recommendations.

References

Colorado State University. 2018. Hemp Russet Mite. Available https://webdoc.agsci.colostate.edu/hempinsects/PDFs/Hemp%20Russet%20Mite_New_6-28-18.pdf

Colorado State University. (n.d.). Hemp Russet Mite. Available https://webdoc.agsci.colostate.edu/hempinsects/PDFs/Hemp%20Russet%20Mite%20Revision%20December%202018.pdf

Pulkoski, M. & H. Burrack. 2020. Hemp Russet Mite in Industrial Hemp. NC State: Extension. Available https://content.ces.ncsu.edu/hemp-russet-mite-in-industrial-hemp#:~:text=Hemp%20russet%20mite%20develops%20in,%2C%20grayish%2C%20or%20bronzed%20leaves.

Utah State University (n.d.). Hemp Russet Mite. Utah State University: Extension. Available https://extension.usu.edu/pests/ipm/notes_ag/hemp-hemp-russet-mite-

Villanueva, R., Viloria, Z., Ochoa, R., and A. Ulsamer. (n.d.). Hemp Russet Mite, a Key Pest of Hemp in Kentucky. University of Kentucky: College of Agriculture, Food and Environment. Available https://entomology.ca.uky.edu/ef162