How to Control Spider Mites
The two-spotted spider mite is the most common pest mite to attack cannabis, other pest mites include: the hemp russet mite, broad mite, oriental mite, privet mite and more. This article focuses on the two-spotted one.
Spider mites are the most common pest in indoor gardens and greenhouses. Find them in dirty garden rooms and ill-kept greenhouses. Use a 10X to 30X handheld microscope to spot tiny mites (0.04-inch long) on the underside of leaves. Look closely and you can see the minute translucent eggs. Spider mites suck the life-giving sap from cannabis, causing loss of vigor and slow stunted growth. The first sign most gardeners see, called stippling, appears on the tops of leaves as tiny white to yellow specks. By the time most gardeners see stippling on leaves an infestation is well underway. Fertilized once for life, a female can lay 20 eggs a day. Eggs hatch in 3-4 days in warm weather.
Spider mites multiply super-fast and adapt to pesticide controls quickly. Once the pest is discovered, using a full arsenal of methods and substances is the only way to make them go away!
Exclude spider mites from your garden room or greenhouse. Spider mites can ride a current of air, hitch a ride on plants, pets and you! Keeping everything inside and around the garden clean is the best prevention. Keep tools clean. Dip dirty pruners in a can of alcohol to sterilize. Keep the garden area clean – tools, floor, walls, benches, pots, everything!
Dip (submerge) all new plants including clones that enter your garden area in a container of miticide.
Temperatures below 60oF and high humidity slow reproduction immensely.
Wipe Tanglefoot? around pot lips, the base of plant stems, and at each end of drying lines.
Remove foliage with more than 50 percent damage.
Introduce predatory mites.
Safe Sprays
Always spray first thing in the morning. Spray leaves, especially undersides with a jet of cold water to blast the off foliage. Lower water pH to 3-4 (acid rain) and spray with gusto.
Insecticidal soap, potassium fatty acids are OK for light infestations.
Homemade sprays include one or a mix of several of the following: Dr. Bronner’s soap, garlic, hot pepper, canola oil, citrus oil, liquid seaweed, milk, etc.
Neem oil, pyrethrum and horticultural oil are stronger sprays. Rotate sprays so mites do not develop immunity.
Stirrup M (cinnamaldehyde) synthetic hormone that enhances miticides.
Floramite is a contact miticide
TetraSan, a mite growth regulator
Apply only non-systemic contact sprays that are approved for edibles – fruits and vegetables. Systemic compounds can be carcinogenic and fatal!
Always follow directions on product label.
See the Cannabis Encyclopedia for expanded control measures of spider mites, hemp russet mites and broad mites.