Hemp Russet Mite

Aculops cannabicola

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Hosts

• Greenhouse and field-grown hemp

Description

Hemp russet mite is a type of eriophyid mite (family Eriophyidae). Eriophyid mites are tiny, (not visible with a magnifying lens) cigar-shaped, and have a pale-yellow or pale-pink body. Hemp russet mites are only noticed after plant damage appears. Mites are best identified under high magnification using a dissecting microscope. They are usually found on the undersides of leaves.

Life Cycle

Egg  | Nymph | Adult

• Multiple, overlapping generations per
  year.
• The life cycle is not yet clearly defined,
  but it appears that mites overwinter in
  crop debris. In greenhouses, they can
  survive year-round with a constant
  food source.

Damaging Lifestage(s): Nymph, Adult

Damage Symptoms

There is no visible damage when mite populations are low. Mites feed on plant surfaces with piercing-sucking mouthparts, killing individual cells and causing fine spotting or stippling. Symptoms appear during high populations. Feeding on leaves can cause bronzing (russetting), which can be accompanied by reduced leaf size, brittle foliage, and upward leaf-edge curling. Stem feeding can cause stem bronzing. 

Time for Concern

Summer through harvest.

When and Where to Scout

• Look for bronzing on lower leaves and stems and other symptoms during hot, dry conditions.
• Use a strong hand lens or microscope to check damaged leaves and surrounding healthy leaves for mites.
• Contact the Utah Plant Pest Diagnostic Lab or your local county Extension office for assistance with diagnosing hemp russet mite. 

Threat Level

High. If not controlled, this pest can severely damage plant tissues, reduce crop yield or cause plant death.

Occurrence in Utah

Hemp russet mites have not been found to cause damage to field-grown hemp in Utah, but neighboring states have reported this to be a major pest.

Management

• Use mite-free seed or starts.
• Remove and destroy infested plant debris.
• Prune and remove infested plants from fields.
• Clean tools used on infested plants before using on healthy plants.
• Promote natural enemies.
• Approved pesticides are available.

When to Consider Treatment

Once identified on plants, insecticide treatment is recommended if cultural practices cannot adequately reduce populations. 

Look-alikes

Spider mites, thrips, or physiological conditions that cause leaf curling and yellowing.

Insecticides for Mites

Utah-Registered Product	Active Ingredient(s)	Notes
Bonide Insecticidal Soap MultiPurpose Insect Control Ready To Use	potassium laurate	Greenhouse use only.
Brandt Ecotec Plus	rosemary oil	Greenhouse use only.
Captiva	capsicum oleoresin extract
Captiva Prime	capsicum oleoresin extract
Dr. Earth Final Stop OMRI Fruit Tree Insect Killer (RTU); Concentrate	rosemary oil	Outdoor use only.
Dr. Earth Final Stop OMRI Rose and Flower Insect Killer (RTU)	rosemary oil	Ground application only to non blooming plants.
Dr. Earth Final Stop OMRI Vegetable Garden Insect Killer (RTU); Conc.	rosemary oil	Before flowering only.
Dr. Earth Final Stop OMRI Yard and Garden Insect Killer (RTU); Conc.	rosemary oil
Dr. Earth Final Stop ProActive Yard & Garden Insect Killer (spray)	rosemary oil
EcoWorks EC	neem oil, cold pressed
Garden Safe Brand Insecticidal Soap Insect Killer	potassium laurate
Kopa Insecticidal Soap	potassiums salts of fatty acid
Leaf Life Gavicide Green 415	mineral oil	Greenhouse use only.
Mammoth Cancontrol	thyme oil
Mite-E-Oil	mineral oil	Greenhouse use only.
M-Pede Insecticide Miticide Fungicide	potassium laurate
Natural Guard Brand by Ferti-lome Insecticidal Soap Concentrate	potassium salts of fatty acids
Omni Supreme Spray	mineral oil
Organocide 3-in-1 Garden Spray Concentrate, Ready to Spray; Ready to Use	sesame oil
Organocide Bee Safe 3-in-1 Garden Spray Concentrate; RTU	sesame oil
Ortho Tree & Shrub Fruit Tree Spray Concentrate	clarified hydrophobic extract of neem oil
Prizefighter	ammonium nonanoate	Many uses including greenhouse.
PureCrop1	soybean oil
Rango	neem oil, cold pressed	Before flowering only.
Safer Brand #567 Pyrethrin & Insecticidal Soap Concentrate II	potassium salts of fatty acids	Before flowering only.
Safer Brand Insect Killing Soap Concentrate II	potassium salts of fatty acids
Safer Brand Insect Killing Soap with Seaweed Extract II	potassium salts of fatty acids
SaferGro Pest Out	cottonseed oil
SuffOil-X	mineral oil
Triact 70	clarified hydrophobic extract of neem oil	Older versions cannot be used on cannabis.
TriTek	mineral oil
Venerate CG; XC	Burkholderia sp. strain A396

Photo Credit

• Whitney Cranshaw, Colorado State University, Bugwood.org

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