This season and next, russet mites are one of the biggest problems that cannabis farmers will face.
Hot and dry conditions across much of the United States have been ideal for these eriophyid mite family parties. These pests are extremely infectious and can spread quickly across or between crops by wind, soil, or even carried on clothes. Russet mites are almost invisible to the naked eye and feast on new growth and trichomes. Without preparation and proper means for dealing with outbreaks, these pests can devastate a crop. This past fall, one of our Clean Green Certified farmers in Southern Oregon was facing just such a prospect.
One day, the owner of Peach Orchard Tree Farm in Josephine County noticed the telltale signs of a russet mite infection that are often mistaken for nutritional deficiencies: curling leaves, stem discoloration and a yellowish powder on the infected plants. “If you’re in tune with it, and know what’s going on, you can see it the moment you step on the farm,” he told us. To combat the mites, he first turned to Organocide, an organic insecticide, fungicide, and miticide. However, spraying Organocide on one of their mite-infested light dep crops ended up killing all the plants. This was when they turned to Evergreen Growers Supply, a beneficial insect supplier in Clackamas County, Oregon.
Both Evergreen Growers and Natural Enemies (a Clean Green licensed chemical-free consulting company) sell pest-predators who prey on mites and other harmful critters but don’t damage your crop. “The only way to get those mites eaten up is by using other bugs,” our Peach Orchard farmer told us,
“We’d kill everything if we put on sprays. They fight the beneficials… they work against the soil.”
He’s right, conventional methods of fighting pests – such as sprays and fumigation, even organic ones – can kill beneficial insects and soil organisms along with the targeted pests. This can have negative long-term consequences for your farm, reducing the yield and health of your crop.
Evergreen Growers helps farmers by providing beneficial insects to treat an outbreak without sprays or chemicals. They can even help diagnose an outbreak if you are not sure what type of mite or insect infection you might have, all you have to do is send them a picture of the damage to your crop. For russet mites, they provided the Peach Orchard Team Farm with three types of predator mites (Amblyseius cucumeris, A. swirskii, and A. fallacis). The beneficial insects proved successful for Peach Orchard, solving their russet mite problem without harming their plants or soil. As an added perk, beneficial insects will often stick around after treating an outbreak, protecting your crop from further problems (see below for list of plants that will help keep the good bugs around).
Natural Enemies’ owner, Shane Young, helps consult growers of commercial cannabis on the effective use of beneficial insects. When treating for Hemp Russet Mites, Shane suggests “always start from the ground up as many pests are introduced from your soil or substrate. Growers need to understand that when using beneficial insects or predatory mites, preventative applications are by far more effective for control than curative techniques”. An effective prevention plan for russet mites starts with a soil dwelling mite followed by applications of Amblyseius swirskii or Amblyseius andersoni sachets. These sachets are breeding bags that hang on the under branches and continually release predatory mites into the canopy of the plant. Growers have also found it very helpful to introduce the same soil dwelling mite, Stratiolaelaps scimitus after harvest. This predatory soil mite does not go into diapause and feeds on any overwintering pests to ensure a cleaner start to the following season.
If you are facing a russet or spider mite problem, Clean Green recommends obtaining beneficial insects from your closest supplier. If you are not yet facing a russet mite problem, think preventatively as these little plant suckers will come by plane, train, automobile and virtually any form of small critter transportation (wind, pots, dogs…). Only use dependable soil from a source that you trust (and don’t be afraid to ask if they have had mite issues). Talk to your insectary about using beneficial nematodes just as soil temperatures begin to warm and ahead of planting to help destroy russet mite eggs and nymphs in the soil before they start to damage the stems of your plants.
Peach Orchard Tree Farm after organic mite treatments described above- click to view images
Below is a partial list of beneficial insect suppliers in states that Clean Green Certified operates.
For a full list of suppliers go to entomology.ca.uky.edu/ef125.
Trusted supplier of beneficial insects and predatory mites for effective chemical free pest management in commercial cultivation. They provide a customized assessment for your farm.
25139 Briggs Road
Romolandm CA 92585
Evergreen Growers Supply
17592 South Palmer Road
Oregon City, OR 97045
P.O. Box 25845
Colorado Springs, CO 80936
Rincon-Vitova Insectaries, Inc.
PO Box 1555
Ventura, CA 93002-1555
Partial Listing of Plants that will Help Keep the Beneficials Around:
EARLY BLOOMING PLANTS:
Aurinia saxatilis, Basket of Gold alyssum (sun, medium height)
Penstemon sp., penstemons (sun, medium height)
Potentilla verna, or other cinquefoils (sun, low growing)
Thymus sp., thyme (sun, low growing)
Aquilegia x hybrida, columbine (shade, medium height)
Ajuga reptans, carpet bugleweed (shade, low growing)
MID-SEASON BLOOMING PLANTS:
Achillea filipendulina, common yarrow (sun, low to medium height)
Aster sp., asters (sun, low growing)
Veronica spicata, spike speedwell (sun, medium height)
Callirhoe involucrate, poppy mallow (sun to light shade, low growing)
Coriandrum sativum, coriander (sun, medium height)
Lavandula angustifolia, English lavender (sun, medium height)
Potentilla recta, sulfur cinquefoil (sun, medium height)
Lobelia erinus, edging lobelia (part-shade to sun, low growing)
Mentha sp., mints (sun, low to medium height)
Sedum sp., stonecrops (part-shade to sun, low to medium height)
LATER BLOOMING PLANTS:
Achillea millefolium, fern leaf yarrow and other yarrows (sun, low to medium height)
Allium tanguticum, lavender globe lily (sun, medium height)
Anethum geraveolens, dill (sun, medium to tall)
Anthemis tinctoria, chamomile (sun, low growing)
Feniculum vulgare, fennel (sun, tall)
Limonium latifolium, statice or sea lavender (sun, medium height)
Monarda fistulosa, wild bergamot (sun, medium to tall)
ADDITIONAL HIGHLY ATTRACTIVE PLANTS:
Annuals or perennials in the sunflower/aster family (many small flowers,petals around a central disk): cosmos, zinnia, small sun flowers, daisy, coneflower
Cabbage, broccoli, mustard, bok choy, and radish allowed to flower
Many herbs: borage, horehound, lavender, chamomile, rosemary, basil
Mints: bergamot, pennyroyal, wood betony, thyme, (some invasive)
Carrot family: angelica, coriander, parsley, dill, fennel, anise
Sage family (Salvia): scarlet sage, Cleveland sage
Pea family: vetch, clover Buckwheats (Eriogonum)
~Provide your beneficial insects with food and habitat in your garden with a variety of plants blooming from early spring through fall. This will encourage the production of all life stages of insect predators and will help reduce undesirable insect pests naturally. Create plantings of varied heights in sun and shade to provide food and habitat for different insect species and life stages–eggs, pupae, larvae, and adults~
Clean Green Certified, www.cleangreencert.com thanks its Southern Oregon farmers for their insight on russet mite issues
Evergreen Growers Supply, www.evergreengrowers.com
University of California Agriculture and Natural Resources Department, http://ucanr.org/sites/sacmg/files/77452.pdf