Hemp russet mites cause damage by feeding on the contents of plant cells, primarily targeting stems and petioles in the early stages. As populations increase, they migrate to the undersides of leaves. Their feeding results in stunted plant growth, reduced leaf size, and suppressed or deformed bud development, ultimately lowering both yield and quality.

Affected leaves may appear dull, greyish, or bronze in color, and the edges often curl upward. In severe cases, buds become dwarfed or fail to develop altogether, making early detection and intervention critical.

The hemp russet mite (Aculops cannabicola) has four life stages: egg, larva (first nymphal stage), nymph (second nymphal stage), and adult. All stages are extremely small and difficult to see without magnification. The mites are torpedo-shaped, soft-bodied, and segmented, with the appearance of two distinct parts: a head with mouthparts and a tapered body. Unlike most other mite groups that have four pairs of legs, hemp russet mites have only two pairs in all mobile stages.

Eggs measure approximately 0.05 mm in diameter and are often laid on stems, petioles, or leaves. After hatching, the larval and nymphal stages resemble miniature adults and continue to feed on plant tissue. Adult mites reach about 0.2 mm in length and are nearly invisible to the naked eye. Their rapid life cycle and microscopic size make early infestations easy to miss and difficult to manage without close monitoring.

Preventing hemp russet mite (Aculops cannabicola) infestations requires consistent vigilance and strong cultural practices, particularly because these mites are extremely small and difficult to detect with the naked eye. A critical first step in prevention is quarantining all incoming plant material. New clones or mother plants should be isolated for at least 7–10 days before being introduced to the main growing area. During this period, growers should use a microscope or jeweler’s loupe (60x–100x) to inspect stems and undersides of leaves for early signs of mite activity, such as leaf curling, dull coloration, or stunted growth.

Good sanitation between production cycles is also vital. All surfaces, tools, pots, and benches should be thoroughly cleaned and disinfected. If possible, a heat treatment between crops—45 celcius for at least 5 hours—further reduces the likelihood of carryover mites. Growers should also be mindful of plant health, as stressed plants are more susceptible to damage. Over-fertilization, particularly with nitrogen, can lead to soft, lush growth that attracts russet mites. Maintaining a balanced nutrient regimen and proper irrigation supports stronger plants that are better able to tolerate low levels of pest pressure.

By integrating these preventative measures into routine operations, growers can significantly reduce the chances of a hemp russet mite outbreak, protect crop quality, and sustain consistent yields.

Hemp russet mite (Aculops cannabicola) infestations, while relatively rare, remain a serious threat—particularly in cannabis greenhouse environments where conditions can support their development and spread. These mites are extremely small and difficult to detect, which makes early intervention and layered control strategies critical. The best approach to managing active infestations involves spray treatments, followed by strict quarantine protocols and sanitation efforts. In severe cases, removing infested plants may be necessary to prevent the spread to healthy crops.

Microscopic wettable sulphur is the preferred curative treatment, especially for spot spraying small outbreaks. It offers residual action even after it dries, and is currently one of the more effective products available.

Soap/Oil are other products for use on cannabis and has been proven effective, although it must not be used in close succession with sulphur sprays due to the risk of phytotoxicity. Proper spacing between applications is essential to avoid plant damage. Coverage is crucial. Make two passes over the plants to ensure all surfaces, including stems and the undersides of leaves, are treated.

Preventative use of predatory mites deployed for other pests (such as Swirski (Amblyseius swirskii) or Spical (Neoseiulus californicus0) can also help suppress russet mite populations if they appear. You can also use them after you have finished using microscpic wettable sulphur, oil, or soap.

A layered IPM approach that includes preventative biologicals, environmental controls, and timely curative treatments provides the best chance of avoiding crop loss and quality reductions from this elusive pest.