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Purple Power

Pest: Hemp Russet Mite

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Pest: Hemp Russet Mite




(Aculops Cannabicola)





There is little known or studied about this mite. Studies are limited on this mite because research wouldn't have been financially feasible or government funded.  In each case study that was done, treatment options were grim at best. I've been pouring over any and every scientific site I can find on Aculops cannabicola the last 3 days.


These white to yellowish-orange, tiny, squirmy, maggoty-looking, and nauseating pests will humble even the most seasoned of growers. This is one of the worst pest a grower can come across because of their size, and they’re effectively disbursed by wind (it's their primary method of spreading). You need a minimum of 14X to see them, some say 20X. You would be wise to also invest in a microscope that magnifies up to 200X, more is better. Because they are so small, you might see damage already done on your plant(s) before seeing them (there maybe be thousands of mites on the plant at this point).  They DO NOT make webs.


Some cannabis researchers suggest documenting strains that seem more resistant to this mite as the only method of control. Karl Hillig, a known cannabis researcher who was involved in the only known greenhouse infestation of Indiana University in 2003, explained he was never able to completely eliminate A. Cannabicola from the gravel floor greenhouse, even after destroying all the plants and fumigating the structure.


It is highly recommended to learn and use the Integrated Pest Management (IPM). It is a method of spotting and controlling pests before they get out of control. The founding principle is that the better you are at detecting and preventing problems early on, the less you will need to rely on pesticides later in the season, or lose your plants.  Once infestations spread up plants, it’s almost impossible to save the plant. They can kill a plant under 8 weeks. Remember, an ounce of prevention is worth a pound of the medicine.



Some may transmit viruses


µm is micrometer; 1 µm = 0.001 mm



Special Species Notes:



They are a species of mite that belongs to the superfamily Eriophyoidae. Hemp and russet mites are part of the Eriophyidae family of mites. About 3,600 species have been described, but this is probably less than 10% of the actual number existing in this poorly researched family. There are more then 200  plant-specific eriophyid species, including gall, rust, and blister mites, the tomato-attacking, microscopic russet mite is among the hardest to detect. Visible, if then, only in clusters, a single mite is too tiny to be seen by the human eye without magnification of 14x and higher.


Also known as the russet mite, rust mite, thistle mite,  Hemp Mites, Hemp Russet Mite, or the Canada thistle mite, or #$!@%$ (usually when spotted).


Like the spider mite, the warmer and drier the weather, the faster Hemp Russet Mites reproduce. Eriophyid mites tend to live together in large clusters and reproduce within the folds of plant tissues.


Eriophyid mites feed deep within the plant tissues (meristematic region), sucking out plant juices with their styletlike mouthparts and inject a poison into the plant as they feed that causes leaf disorders and  deformation of plant growth for several feet upward in the plant. The mites feed on the inflorescences of both sexes, and may effectively sterilize both the male and female plants.  Eriophyid mite feeding can result in a variety of symptoms, including galling, clustering or, witches, broom, swollen or thickened growth, leaf blistering, and russetting or bronzing of leaves. Eriophyid mites may be categorized based on the type of injury they cause to plants, with the two primary classifications being (1) those that create galls (gall-formers) and (2) those that stunt new plant growth.


Most people think their plants have mosaic virus, a nutrient deficiency, or other form of plant stress when it's the russet mite. If you see what looks like a pale, brown/yellow powder or dust, take a closer look at the 'dust' with a magnifier or microscope. They may be also confused for light brown mold spores. It might not be innocent dust, it might be these bastards. 






Other Eriophyidae Species used as biological control of pest weeds


The Eriophyidae family of mites are a specialized group of plant feeders. Eriophyids are selective in their choice of host plants, and each species prefers a narrow range of a few closely related species or genera of host plants. Meaning that the species found on one plant species will not usually feed on other plant species. Since there are literally hundreds of species known and others still waiting to be identified, two species of plants may both be infested with eriophyid mites, but with different species of mites. About 80% of currently known species of eriophyoid mites have been recorded in association with a single species of host plant. Additionally, eriophyid mites are the only group of mites known to transmit plant viruses.


Eriophyid mites have been considered to have a high potential for use as classical biological control agents of weeds. 13 species have undergone some degree of pre-release evaluation (Aceria genistae,A. lantanae ,Aceria sp. [boneseed leaf buckle mite(BLBM)], A. salsolae,A. sobhiani,A. solstitialis ,A. tamaricis, A. thalgi, A. hessalonicae, Cecidophyes rouhollahi, Floracarus perrepae, Leipothrix dipsacivagus and L. knautiae ), but only four ( A. genistae , Aceria sp. [bLBM], C. rouhollahi and F. perrepae ) have been authorized for introduction. Prior to this, three species (Aceria chondrillae , A. malherbae and Aculus hyperici ) were introduced and have become established. Although these three species impact the fitness of their host plant, it is not clear how much they have contributed to reduction of the population of the target weed. In some cases, natural enemies, resistant plant genotypes, and adverse abiotic conditions have reduced the ability of eriophyid mites to control target weed populations.


Some eriophyid mites that are highly coevolved with their host plant may be poor prospects for biological control because of host plant resistance or tolerance of the plant to the mite. Concerns that eriophyids may be more likely to lose efficacy over time due to coevolution with the target weed or that they may be more likely to adapt to nontarget host plants


 Aceria chondrillae is native to Europe and has been introduced to control Chondrilla juncea L. (rush skeletonweed)


 The Vieste, Italy strain of the mite induced galls on all three N. American plant accessions tested, but not on the Australian narrow-leaf form. In California, the introduced mite is widespread and densities can be high in Sacramento and Eldorado counties The mite is widespread in Oregon and Washington, and in some areas it may reduce flowering and seed production by 50–90%, depending on plant size and environmental conditions. Some mite were accidentally released and found new host plants.


 In some cases where eriophyids appear to survive long periods under extreme cold, desiccating conditions and low oxygen concentration, suggests the potential for long-distance aerial dispersal (Zhao and Amrine 1997). For example, some species held in water at about 39F (4C) survived for up to 5–6 weeks.









Aculops cannabicola at 700x


Since they are even smaller than spider mites, they often go undetected. Russet mites tend to prefer similar warm, dry conditions.  Russet mites are usually not visible unless they are present in great numbers, when they clump together and can look like a pale dust.


They are less then 0.2 mm long (, 20-170µm long and 65 µm wide- µm is micrometer; 1 µm = 0.001 mm), and are thus almost invisible to the naked eye. They are smaller than dust mites and thinner than human hair. Under a microscope, they’ll look like a small worm with 4 legs on the front. Female specimens have a  cylindrical/cigar-shaped, tapering from head to rear and light orange. 195-210um long, 62-70um wide. Males are smaller 160-165 um long, 55-57um wide. nymphs 170-172um long, 60um wide. Larvae 110-112 um long, 45-47um wide.


Depending upon the stage of development, both nymphs and adults can appear white, tan, pink, light orange or yellow. Unlike most mites, eriophyids only have 4 legs located near the head.


Adults and nymphs have piercing-sucking mouthparts and feeding on the undersides of lower leaves and on petioles and stems produces a greasy appearance, which becomes bronzed eaves may yellow, curl upwards (like a taco), dry out and drop. Damage starts at the bottom of plants and moves upward and may be confused with nutritional deficiencies, plant disease or water stress.






How it spreads:


Russet mites don’t move very far on their own. Originally they were described from eastern Europe by Farkas in 1960, this species appears to presently have a broad distribution worldwide through human-assisted spread. Russet mites hitch rides on other insects or the wind ( light breeze) to spread to new areas, even a splash of water. Russet mites can hide in contaminated potting soils as well, or can be introduced by bringing in clippings and clones of infected plants, on seeds, clothes, nearly anything. It’s been reported that strong airflow from commercial atomizers can spread them around the garden.


I highly recommend strict quarantine measures: any new plant (cutting or clone) be in a quarantine area. take a shower before visiting any other garden. Don't forget to wash your cloths, towel asap. Wear different shoes when in quarantine area. Sterilize your soil even if new. Change air filters regularly. 


This link is to the quarantine thread:      http://freemygreenpdx.com/topic/14249-quarantine-what-is-it-and-why-do-i-need-to/






Life Cycle


Little is known about it life cycle, but here is what I found.   


Life span is 20-40 days. I was unable to find out if this is from egg to adult or once are adult living this long. From egg to adult 10 days to 2 weeks-4 weeks. Their developmental time varies based on environmental conditions; it takes them 15 days to reach adulthood in cool weather, but that accelerates to 8 days during the warmer summer months. The egg to adult period is less than a week in warm weather.


At 80ºF (27ºC) 70% RH,  hemp russet mites achieve a 30-day life cycle. Keep the garden below 70ºF (21ºC) and below 50% humidity to slow reproductive process.


These mites produce multiple generations each year, and probably overwinter under bud scales of the thistle, on roots, the root buds, or inside the stems of affected plants as well as at plant joints, and can be active year-round. This mite normally spends the winter as fertilized female adults. They continuously reproduce during times other than winter, creating a new generation every two to three weeks. It can take as little as eight days to mature to adults. They emerge in the spring.


The eggs are spherical/round and generally laid in groups, although they can be laid individually. Eggs are laid on the undersides of leaves, on leaf petioles and on stems on the lower portion of plants. It is unknown how long the eggs can lie dormant. They hatch in less than 2 weeks into young mites that may take about 2 weeks to a month to mature into adults. The reproductive potential of eriophyid mites is very similar to twospotted spider mite, Tetranychus urticae. Each eriophyid female mite may lay up 50 to 100 eggs a day-  giving rabbits a run for their money. A single breeding pair of rabbits can produce more meat in a 12 month calendar year then a steer in the same time frame.


Following the egg's hatching, russet mites go through two developmental nymph stages, which resemble adults but are slightly smaller. The two nymphal instars usually do not move far from where they hatched and tend to congregate on the edges of leaves.


Adults remain tiny, are wedge-shaped, and appear yellow (particularly in clusters). They differ from many other mite species in that they only have two pairs of legs (4).


When damage to lower plant parts increases, the mites move up to younger foliage. As plants begin to die, mites may gather at the highest parts of the plants and are picked up and spread by the wind.


Host plants


This mite is Cannabis specific, and will feed on all kinds of cannabis like the European fiber.



First Sign:





Signs of damage. see the 'dust' on the stem? that the mites



Unlike spider mites, these voracious plant pests leave no webbing or other secretions when present. Visible damage to the plant is the first indication of its presence. Damage is often mistaken for mineral and other nutritional deficits. Like spider mites, the mites are sap suckers and will also feed on leaves and leaflets. However, the russet mites also eat the petioles (leaf stems), fruit, flowers/buds, new growth, pistils (this make the plant sterile), even glandular trichomes, and can even survive for a short period of time on dried buds. They severely reduce resin production.


Look for underdeveloped new growth, drooping, leathery leaves, and curled or drying/crispy leaf edges (you’ll see discoloration and “burning” on the leaves) with bronzing of leaves and stems bottom to top. Leaves can turn yellow and might fold into a taco shape or fall off. It is very easy to mistake the damage for a deficiency or simply over watering. They start by feeding on the lower structures of the plant, then work their way up as the food supply is depleted.  Russet mites are especially attracted to flower resins and can go unnoticed while feeding in flowers.


Early signs of distress include progressive curling and drying out with bronzing of leaves and stems bottom to top. This is often ignored as just a bit of water stress or nutrient deficiency. Those leaves are sucked out and done, yesterday’s dinner, that’s not where the mites are now. Go up a level and microscopically inspect both sides of a few leaves including the stems directly above the damaged, unhealthy looking lower foliage.


The visible symptoms created by the russet mite are very similar to other common problems.  Fan leaves might curl a bit at the edges and have a glossy wet look- similar to heat stress.  Leaves may have yellow or bronze spotting – sometimes also a symptom of mosaic viruses.  New growth may come in twisted and seem stunted/limited or leaves might droop – as if the plant is suffering from environmental stresses or nutrient deficiency.


Given the russet mite life cycle, treatments can take several weeks before the infestation is eliminated, and because the mites easily spread through wind, vigilance is required to prevent re-infestation.  Under ideal conditions, a single mite may live a month (or more) and lay many eggs during that time period.  When the eggs hatch, the cycle starts all over again.


To put this in perspective, let's keep this simple and take out the temperature and RH that can speed up or slow down their cycle. we'll go with a simple 30 day life cycle.  It's likely you won't detect something wrong till 2 cycles have passed due to the fact that they do little damage in the first cycle. Based upon their population, their infestation can be categorized in 3 stages.


The first stage is when the eggs are laid, usually on the bottom of the leaves. The hatched larva will eat a ring around the egg. Look for a very small brown ring to give you indication of their presence. If you were a good person in your past life and the gods were smiling upon you then you'd find these nearly invisible pests in their first stage while using the Integrated Pest Management (IPM) method,..... but odd are against it. The common mistake here if anything is seen is thinking a mineral (calcium and magnesium),  other nutritional deficits, or environmental stress.


In the 2nd stage, you will see more brown spots appearing despite trying to address mineral, other nutritional deficits, or environmental stress. No amount of cal-mag makes any difference. Your test results show mineral and nutrition are in the normal range. The plants however are screaming something is wrong.  If you had cropped and pruned your plants (put the waste in sealed plastic) their might be an orange discoloration around exposed sap where they have come in for easy feeding. You may notice your plant looks 'dusty', for example on the stem of the leaf.  By now there has most likely been 2 thirty-day cycles and if you look under a microscope you will see eggs, larvae, and adults (when they are together they look like light dust).


By the 3rd stage, you will see a lot more damage, especially to the lower bottom of the plant, then they work their way up as the food supply is depleted.  New growth will be stunted and deformed, and they are especially attracted to flower resins that can go unnoticed while feeding on buds until they appear withered. Increasing in numbers, the pests will spread to all parts of the plant, and will eventually take all the sap from the entire plant.


Anyone scared yet? You should be. Once infestations spread up plants, it’s almost impossible to save the plant..... and the mites are most likely in the entire garden on everything- plants, equipment, floor, walls, ceiling, anyone and thing that's been in there and you. If you're lucky these mites haven't spread from your grow room to your car, house and pets.








What to do: IPM


The best controls for both indoor and outdoor growers are preventive methods.


Avoid over-fertilizing plants. Mites are attracted to vigorous green growth that comes of too much nitrogen.


Foliar Spray Regularly while in Veg. A foliar spray of Silica and Kelp will help strengthen plants and make it more difficult for mites to get a foothold, while also helping to keep humidity levels up. Watch out for powdery mildew when increasing RH levels. If outdoors, do this in the morning, so the extra moisture will evaporate during the day. Foliar Spray also keeps the real dust off of the plant that can attract mites.


Removing weeds and other vegetation near your crop that could harbor mites. This why my outdoor area looks like a desert with chickens running around.


IPM: Regular and close scrutiny of your plants, especially around the leaves nearest the soil line if outdoors, or anywhere a plant is flowering, is crucial to early detection.


I drought sticky traps would help with these mites, however it is a good idea to have them out for other pests.


There are several beneficial insects eat russet mites that can be released as a preventive and there is beneficial insect food available too. In beneficial insect below.


Since mites like hot and dry climates, keeping the garden cool and moist. it'll help slow their reproductive cycle, giving you time to deal with an outbreak. Good airflow. Proper ventilation and humidifiers can help accomplish this with indoor plants. This can also help keep mites at bay, making it more difficult for them to start building and maintaining a footing when the leaves and stems are in motion. Air flow is also good at keeping spider mites at bay cause of their webbing.


Indoors, exclusion is the best preventative. Quarantine new plants, disinfect tools, use HEPA filters on incoming air ducting; generally respect the cleanliness and integrity of your grow space like a medical clean room. Consider soil-less, hydroponic grow methods to reduce the chance of introducing Hemp Russet Mites. If using soil, use the pasteurized process to Solarize it. For more information on how to click the following link. It's post #5:   http://freemygreenpdx.com/topic/14249-quarantine-what-is-it-and-why-do-i-need-to/


This bears repeating, eliminating dust and debris is crucial to denying mites in your garden. It is also the easiest thing to let slide when life inevitably interrupts your garden time. However, it is worthwhile to make cleanliness a top priority. Make sure you don’t introduce mites into your grow space by bringing in infected plants or contaminated potting soil, or on you ( carries females and/ or eggs). Keep a clean grow space. Don’t introduce unnecessary tools used outside or suspect soil or growing mediums. That quick fix, may just cost you your garden of medicine.


Prune away, quarantine and safely dispose of any early isolated infested material (sealed plastic bags); don’t be shy about sacrificing a few leaves, Colas or even an entire plant for the sake of your remaining crop. Keep checking to see if damage has stopped. I check my garden bare minimum twice a day sometimes more.


Prevent spreading mites. Discard infested plants in plastic bags and dispose of them in sealed garbage containers. Think hazmat here, you don't want to spread any pest, especially these around your house, car/truck, or property/yard.


Mites feed on a wide variety of plant. Even if you don’t see any signs of them in your garden, always play it safe. Shower, wash your cloths and towel, change clothes ASAP don't even touch your indoor pets until you have,  if you’ve been working in your outside garden or yard (mowing lawn) before entering your indoor garden or greenhouse, take a shower, new clean cloths and shoes.


Be exceedingly careful when accepting outside clones into your garden. I always have a magnifier with me.  Grow from seed when possible if seeking new genetics (look at the seed 1st, remember they are so small they could be on the seeds). Always quarantine, even if they are from a “trusted” source.... sometime sh!& happens and they be unaware there is a pest, and didn't treat the outgoing clones. I'm probably rare here, but all my out going clones are treated.  See if you can check out the garden and mother plant(s) the clones are coming from before you take them home. Some growers will not allow other people in their grow room and it is understandable, but you can ask. but be prepared to take a shower first...... and after.


If in doubt, treat for mites as well as adjusting nutrient solutions or amending soil. For indoor grows, adjusting environmental factors outside of optimal range (below 70F) at the 1st sign of mites, reduces their breeding environment by adjusting room temperatures and moisture content (below 50% RH) as much as possible. This will slow the breeding cycle, but not kill mites, buying you time to inspect and treat plants before the mites next generation is spawned. Mites don’t survive well in temperatures over 105-115 F.  Russet mites prefer drier climates and breed more slowly in higher humidity. Remember changes to environmental factors will affect your plants too.


If you have identified mites in your garden, stay on top of manually removing damaged leaves to help keep populations in check. A garden hose can be very effective at knocking mites and eggs from a plant even though it doesn’t kill them directly. If your grow space has been infected, clean it from top to bottom. Scrub benches and other equipment (lights, cords, wall, ceiling, floor, door, pots, carpet- vacuum and carpet cleaner, etc) with a mild bleach solution (1:10 bleach-to-water solution is said to be safe for cleaning according to the Centers For Disease Control), sterilize all hydroponic equipment, throw away any soil that can’t be sanitized, and leave nothing that was in the space during the infestation unscrubbed. The invisible eggs of this troublesome pest can survive in tiny unseen places. You may consider after cleaning the ceiling and walls to repaint.


If you don't have success with this then I painfully suggest you swallow your tears or get a tear bucket and... torch your garden and start fresh! Bleach your workspace from top to bottom including benches, equipment (includes wires to and from them), walls, floor, ceiling and literally everything else. Throw away soil, you want everything new and sterilize it before using.




Diatomaceious Earth won’t get rid of an infestation but will slow down the spread of the mites.



Alcohol spray
Alcohol kills adult mites on contact and evaporates quickly, so plants tolerate it well. Mix half Isopropyl Alcohol with half water and use as a spot spray.


If you have the proper permits, you can use Abamectin on tomatoes to kill Russet Mites. this level of chemical warfare while okay on food is a major No-No for Cannabis almost anywhere. In Oregon, for instance there is a Guide List of what may be applied, and Abamectin is not on the list. Abamectin are fine to use on produce, but not Cannabis because it is Medicine. A pesticide popular with Organic Cannabis growers, Guardian Mite Spray, whose label listed only natural organic active ingredients such as cinnamon oil, was ordered to cease all sales when a lab discovered Abamectin in the mixture.


from my reading, Insecticidal Soaps and Herbal Oils seem like a waste of time and money against Hemp Russet Mites.


Capsaicin and essential oils. Rosemary essential oil and capsaicin kills mites on contact, and is gentler on plants than some of the other foliar sprays included on this list. It can also be a good alternate or spot spray.


Azadirachtin Concentrates   I didn't see russet mite on the list of target pests

These are extracted from neem so that there can be better control over formulation and dosing. Azamax is a popular brand. It can be applied as a foliar spray or root drench. This allows Azadirachtin to act as a systemic pesticide. Although it’s not very toxic to humans, always follow the manufacturers instructions carefully when applying any pesticide, organic or not. Wait 48 hours after application to release any beneficial insects.



Neem oil may be helpful prior to releasing beneficial insects.  Wait 48 hours after application to release any beneficial insects. if applied at the first signs of infestation.


I read somewhere about enzyme products such as Dr. Zymes or Big Time Exterminator, both of which are organic. Spray the whole plant (don't forget the under side) using an atomizer every three days for at least 3 weeks.  sprayed up to 2 weeks before harvest, have flowers tested at a lab - no evidence of Russet Mites on the buds. Wear a respirator while spraying. colloidal silver solution


Sulphur dust/wettable Sulphur (not to be used on flowering plants!) Sulfur has long been used for mite control. Full coverage is necessary for control. during the vegetative growth phase and is safe so long as no oils such as Neem are used for a few weeks before and after the application. Do not apply when temperatures exceed 90°F, or during periods of high humidity. Indoors, use a Sulfur Burner, but remember that the fumes of burning Sulfur are quite hazardous to humans.


Azamax will discourage mites from feeding and slow their breeding cycle, especially helpful if you’re moving towards harvest. Wait 48 hours after application to release any beneficial insects.


Spinosad and Spinosyn A
Another bacterial derived insecticide bacteria (actinomycete Saccharopolyspora spinosa), Spinosad acts on contact or ingestion to inhibit neuron function in insects. Spinosad is also effective at fighting caterpillers, spider mites, and many other marijuana pests however I did not see the russet mite on list.  However,  it is safe for people and pets. Most spinosad products are effective for only about 24 hours after being mixed with water, so only mix as much as you will need per application. Even small doses can be lethal to honey bees, so use extreme caution when applying outdoors.


 Avid, Abamectin
Sourced from bacteria, this miticide acts on the nervous system paralyzing mites. It is approved for use on food crops, but should still be applied with great care and caution to avoid irritation or over-exposure. This should be a last choice effort.


Systemic Miticides, Foggers and Bombs


Before you take this step please carefully consider your safety and do your own research to make sure you fully understand the risks and necessary precautions. Most of these substances will require full protective clothing including gloves, goggles and a respirator. Many are listed for use on ornamental plants only. Please also take into consideration how long these chemicals will last in your plants. Consider whether it may be safer and more expedient to cull badly infested plants.


Forbid 4F
The active chemical in Forbid 4F blocks fat synthesis in mites causing them to dry out. This is similar to how potassium fats in insecticidal soap work. Forbid is not a systemic pesticide. However it is absorbed by the plants leaves so full saturation is not as critical


Floramite SC
This pesticide kills on contact and lasts 21 days. It should never be used past the vegetative cycle. Floromite SC‘s downside is that if mites are not wiped out with the initial application, they will have several generations to develop resistance from a single application.


The label on Floramite they specific "It is not effective against rust mites, broad mites and flat mites."


These are synthetic versions of Pyrethrin. Unlike their organic counterpart they tend to linger in the environment, and are more toxic to humans and animals if inhaled or absorbed through the skin. Total Release foggers often use pyrethroids as their active ingredient


Other Systemics, Acephate
These are found in products like Bonide System Insect Control. They work much like an insecticidal soap, but linger within plant tissue for around five days continually killing adults.



Beneficial bug:


Predatory Mites should be introduced as a natural preventative if Hemp Russet Mites or Spider Mites are known to have been a problem in the past. Periodic releases mite predators such as:



you can introduce Hypoaspis miles (also known as Stratiolaelaps scimitus), a predatory soil mite. are small mites that lives on the soil surface. They can help control russet mites as they hatch in the soil. Hypoaspis should be applied to the soil at a rate of 5,000 per 200 sq. ft. of soil. They will help with early stages of russet mites, so apply soon after the plants are in soil and reapplied every two to four weeks.


link http://freemygreenpdx.com/topic/14451-beneficial-fungus-gnat-predators/


Neoseiulus californicus, Amblyseius andersoni have been used in the past to control spider mites, but also work great against russet mites. They are slightly more cold-hardy than other predators, so they can be used when daytime temperatures are a little lower (mid 60s.) Application rate for traditional crops is three predators per 10 sq. ft., but for russet mite control on cannabis you may easily increase that by tenfold. 


Amblyseius cucumerisAmblyseius fallacis can be made to control established russet mite populations, but are most effective when introduced early in the mite population's development. Amblyseius swirskii are very effective predators of russet mites. They should be used as soon as the temperature is above 70 degrees. for large plants use 250 to 1,000 per plant for a bad russet mite outbreak. For prevention on smaller plants reduce the amount used. A. swirskii can also eat certain stages of thrips and whiteflies. Galendromus occidentali,  a predatory mite that eats spider mites and  russet mite, and native to the western U.S. 40-80%RH, 26-35C    


Post 9 has more info on these predator mites




Nematodes:   They are an inexpensive control for russet mites emerging from the soil and will help control virtually any pest with a soil stage. Apply at a rate of one million per 2,000 sq. ft. Just as soil temperatures begin to warm and ahead of planting can help destroy eggs that are in the soil and nymphs once they hatch. Apply a second round.





The fungus, Hirsutella thompsonii, is a pathogen to hemp russet mites, but I have not seen it available commercially.


One of the newest biological product. BotaniGard 22WP Biological Insecticide 1lb (1lb/$84) 






The link below will take you to "An Intro to beneficial bugs and beneficial insect food" it has a list (been worked on) to pests and beneficial insects




Classy, sassy, and a bit of a smart assy

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Amazing summation of the info out there, and thank you most especially for the predator and genus info.   While the HRM seems to have been rampant since at least 2010 in California, Michigan and points between, there remains little solid information about it out there.  These mostly anonymous internet postings are made and not always followed up by people who are very reasonably freaking out. 


Some things I've noticed from rotating my control methods after pruning to growing tips:


  • They REALLY prefer the underside of the leaf and the center of the plant until control is effective, then they head for growing tips if they can
  • Azatrol + iso killed most adults, but doesn't touch the eggs.  Dips was very effective on adults.
  • citric acid seemed mildly effective on eggs and reasonably effective on adults - is listed as the active ingredient in Dr. Zymes
  • Horsetail + nettle tea seems useful as foliar on babes, but who knows?  A friend had good luck w/ adding an insane amount of DE to soil prep outdoors
  • Spinodaid didn't seem to have any effect
  • I finally found a living A. swirskii on an infected plant it looked like a hollywood creature under a 100x scope with the killing action.  I think if enough living adults were introduced, they would be effective, but my trial packages were mostly DOA.  I would try again.
  • Grandevo slows 'em down, but does nothing to the eggs.  I think is a useful preventative with plenty o' silica -- it seems to make them appear drunk and eventually kill,  but with eggs poppin'....  However, big + : can be safely used up 'til day of harvest and is apparently made from bacteria and dried wine must
  • pyrethrin + neem oil + hort oil was appears to have been nearly 100% effective on several badly infected plants, but only when applied excessively, to the point of some actual leaf damage, even under low light (clogged pores, I think).  Seems to be the only thing I've tried so far to actually halt hatching.  Hort oil alone might do it for continued egg suppression once adults are dead and dying.
  • They are so small, it's impossible for a regular droplet to penetrate though all that hair, esp near veins, and they seem to stick their heads right into the epidermis sometimes and sort of hibernate there.  I think extra iso and dr. bronners wherever possible helps penetrate to their hiding spots and breaks droplets up fine enough to effect them.


I have yet to try the imidcloprid I got or abamectin, cuz there's a line there, you know?  I'm almost there, but not quite until I am convinced there is actual control at the other end.  From my reading, it didn't seem that harsher chemicals were always that much more effective -- that the control was more cultural and preventative-based.  But, people have beliefs about these things...the sort I'm surely not immune to. 


Then again, I've not quite won yet...the eggs, physical smallness and reinfection really are the crux of the problem.  I suspect they are actually killed by many things if you can get it in them.


I also spray my hands with alcohol whenever I touch an infested leaf or move between plants.  I also dip my thumbs and snips habitually in ISO whenever I touch something that doesn't seem right.  I also hit the trimmings with an iso spritz when going out of area for disposal or adding any badly infected material to the temp bucket.


Three things listed I wonder about:

  • sucrashield (no longer made, but still available online)
  • pfr-97
  • met-52




sillydog sez, "Dope grows."

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Hello Purple Power! thanks for all the great info, much appreciated! I was most curious about Forbid 4F and i see that you said it was a non systemic product..i have been trying to figure out if it really is or not..so I called the bayer company and they told me it def is systemic..i wanted to let you know for safety purposes. thanks and happy farming! 

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