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russet mite control on cannabis

Hemp Russet Mites

Hemp russet mites are tiny bugs that attack cannabis plants. In fact, they are so small you can only see them with a magnifier unless there are thousands of them infesting your plant. They live the the crevices of leaves, stems or buds, and the initial symptoms are not that serious. Many growers may not realize they have a bug infestation, and it’s common for growers to confuse the symptoms for other problems such as mold, fusarium, pollen, tobacco mosaic virus , overwatering , a nutrient deficiency or heat damage .

You may see curling on the edges of leaves, and buds may start dying (hemp russet mite leaf damage picture by thehumboldtlocal)

Hemp russet mites are tiny. You often won’t see them until you have a full infestation. They may appear as a beige or yellow mass (typically towards the tops of the plant). This hemp russet mites picture is by grow.nation.

The following two pictures of Hemp Russet Mites (Aculops cannabicola) were taken in Bloomington, Indiana by Karl Hillig. This picture shows hundreds of microscopic mites on the petiole of a Cannabis leaf.

These microscopic four-legged mites infested Cannabis plants in a greenhouse at Indiana University. This picture shows them on a leaf petiole that was about 2 mm wide. By Karl Hillig.

Symptoms of hemp russet mites on cannabis include:

  • Symptoms often worst towards the tops of the plant
  • Bugs are pale, typically either tan or yellow. In big enough numbers they can cause parts of the cannabis plant to look beige or yellow.
  • Sometimes mistaken for fungus, mold or pollen.
  • Tops of plants droop, especially where there is a big infestation
  • Curling of the leaf edges (on some plants)
  • Dull-colored and leaves or stems, which may also become brittle. These affected areas are where bugs are living inside the plant tissue.
  • Brown or yellow spots (from leaf stress, not visible bites)

An intense hemp russet mite infestation on cannabis plants can be difficult to diagnose because it’s hard to see the individual bugs

The yellow mass isn’t mold or pollen. It’s actually an infestation of hemp russet mites

About hemp russet mites

  • Can reproduce and attack cannabis plants all year round
  • Most harmful in the flowering stage when buds get infested
  • Indoors, fans can spread mites

Unfortunately, hemp russet mites are one of the toughest cannabis pests to get rid of. They lay their eggs inside the plant which makes it very difficult to kill their eggs.

  • Grow from seeds (hemp mites and eggs cannot survive on seeds). If you start from seeds, your plants will not get hemp russet mites unless they get infected by some other source
  • Treat and quarantine all new plants (even if they seem healthy) to ensure they don’t have hemp russet mites (or spider mites)

Time to get rid of hemp russet mites for good.

Solution: How to Get Rid of Hemp Russet Mites On Cannabis

Once you’ve actually identified that the bugs you have on your cannabis are hemp russet mites, it’s time to get rid of them! When it comes to hemp russet mites, a lot of the “standard” miticides are not as effective and you’ll notice these particular mites aren’t listed on the labels.

Hemp russet mites can be one of the toughest marijuana pests to get rid of, but it can be done if you stay vigilant!

  • Consider tossing your plants – I know it can be a hard pill to swallow, but if you have an intense infestation, sometimes the easiest thing to do is to get rid of the plants, treat the room thoroughly, and start over. However, make sure you know where you got the mites in the first place or you may end up infected again!
  • Treat often – You may have to treat several times a week or even daily if you have a terrible infestation that won’t go away. This can be very difficult on your plants.
  • Spray Before Lights Go Out – Whenever treating plants with a spray, do it before the lights go off so that your plant is less likely to get burned!
  • Read Instructions – Make sure to read the full instructions of each bottle and follow them when treating your plants. You will save yourself a lot of big headaches!
  • Repeat treatments weekly for 5 more weeks after mites are gone – After you think hemp russet mites are completely gone, don’t stop! Treat your plant with a different treatment at least once a week for 5 additional weeks. If you don’t completely eradicate them they’ll come back with a vengeance and be even more resistant to whatever you throw at them.

1.) Neem Oil

Neem Oil will leave an unpleasant taste/smell on buds when used to treat flowering plants, so again, don’t let this stuff get near your buds! There’s also some evidence Neem oil may be harmful to humans so use with care! That being said, Neem oil is an all-natural remedy that is very effective against many different types of bugs and mold, including hemp russet mites.

Neem oil can be rough on your plants so you don’t want to use it more often than you have to because your plants will suffer. However, if you get desparate treating plants daily with Neem oil is very effective at killing hemp russet mites when nothing seems to be working.

You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly, since neem oil and water can separate easily.

2.) Essentria IC3

Essentria IC3 Insecticide is a mix of various horticultural oils that is organic and safe for humans. It is often marketed as a “bed bug killer” but it can be effective against hemp russet mites when the plants are treated regularly. Unfortunately it only stays effective on the plant for about 8 hours so you will want to either apply this daily or combine with other options. You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly.

3.) Insecticidal soaps

Fatty acid salts or insecticidal soaps can be a good choice against hemp russet mites. They weaken the outer shell of hemp russet mites but are safe to use on your plants and they don’t leave much of a residue which could kill beneficial bugs in your garden.

With soaps, just like horticultural oils, coverage is very important as it does not stay on your plant for long, so follow-up applications may be necessary. Although this is considered safe, avoid getting any on your buds!

This will not get rid of hemp russet mites on its own, but it is less harsh on your plants than some of the other options and so it can be a great way to supplement the other treatments you’re doing.

Natria Insecticidal soap can be a good option Another insecticidal soap that can be used against hemp russet mites is Safer Brand Soap

4.) Mighty Wash

Mighty Wash may help rid your grow room of hemp russet mites. Spray plants 15 minutes before lights out, making sure to drench the foliage under the leaves as well as the top of your soil. You want to use a spray bottle or mister. Use a fan to blow on your leaves to help things dry. Treat your room more than once, even if you believe the hemp russet mites are gone.

Use Mighty Wash with a One-Handed Power Sprayer for the best results!

5.) Avid

Avid miticide is strong stuff with harsh chemicals, and is incredibly expensive, but it can sometimes do the job when nothing else is working. This is a systemic insecticide, which means it works by infiltrating the inside of plant tissue and killing bugs that way. Because of that it should NOT be using in the flowering stage (you don’t want this stuff inside your buds). However, many growers report that this is the only thing that consistently works for them. Always use Avid as directed and only as a last resort! You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly.

Don’t use this product more than once or twice in a row or your mites may become resistant. This should stay in your plant’s system for several weeks. If you’re going to be using systemic insecticides, switch back and forth between this and another one like Forbid. Make sure to follow the instructions!

6.) Forbid

Forbid miticide is sort of like Avid in that it is made of strong stuff with harsh chemicals and is also expensive. This is a systemic insecticide, which means it works by infiltrating the inside of plant tissue and killing bugs that way. Because of that it should NOT be using in the flowering stage (you don’t want this stuff inside your buds). However, many growers report that this can be the only thing that consistently works for them. Always use Forbid as directed and only as a last resort! You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly.

Don’t use this product more than once or twice in a row or your mites may become resistant. This should stay in your plant’s system for several weeks. If you’re going to be using systemic insecticides, switch back and forth between this and another one like Avid. Make sure to follow the instructions!

7.) Diatomaceous Earth

Diatomaceous Earth is basically fossil dust which you mix in with the top of your soil, and anywhere else in your room (window sills, doorways, etc). This powder-like substance is harmless to mammals and plants, but is incredibly sharp at the microscopic level. Therefore it will tear and dehydrate hemp russet mites on physical contact. This will not get rid of an infestation, but can help prevent, control and slow things down when used effectively! When it comes to hemp russet mites, you want to use every tool you can!

8.) Heat

Hemp russet mites don’t like the heat. Some growers will try to get rid of them by on small plants or clones by dunking the plants in hot water (105°F / 40°C) for 10-20 minutes. I’ve also heard of growers try to reduce their number by overheating the grow space to 115°F (46°F) for an hour. Be careful as this can be dangerous if you don’t take safety precautions, and any heat method strong enough to kill the mites will likely hurt your plants.

9.) Predatory Mites

Some types of predatory mites, like Amblysieus andersoni mites, may target hemp russet mites. Supplementing your garden with extra predators can help bring down hemp russet mite numbers. However, it’s not enough to fix the problem on their own and unfortunately a lot of the other remedies on this page may also kill predatory mites.

If you don’t want to use any pesticides, get predatory mites to help eat all your hemp russet mites!

Plant Symptoms

  • Bronze or brown patches
  • Brown or slimy roots
  • Brown or yellow leaf tips/edges
  • Buds dying
  • Buds look odd
  • Bugs are visible
  • Curling or clawing leaves
  • Dark leaves
  • Drooping plant
  • Holes in leaves
  • Mold or powder
  • Pink or purple on leaves
  • Red stems
  • Shiny or smooth leaves
  • Spots or markings
  • Twisted growth
  • Webbing
  • Wilting leaves
  • Yellow between leaf veins
  • Yellow leaves

This page is part of our Plant Doctor series. You can use our tool to filter by symptom and help diagnose your plant.

Hemp Russet Mites Hemp russet mites are tiny bugs that attack cannabis plants. In fact, they are so small you can only see them with a magnifier unless there are thousands of them infesting

How to Prevent and Get Rid of Spider, Broad and Russet Mites on Your Cannabis

SPONSORED BY

Spider mite webbing. Photo by W. Cranshaw, CSU, Bugwood.org

Mites

The term “mite” encompasses thousands of different arthropod species, most of them well under one millimeter in length — roughly the size of the head of a pin — and the largest mite common to cannabis is roughly half that size.

Mites are vectors for infections, but their main damage is the sucking out of nutrients from the plants’ leaves, which interferes with photosynthesis. Draining liquids and nutrients from the leaves slows down the plants’ growth. This, along with vectors they can carry, and excrement and secretions lead to telltale damage in new growth.

Three types of mites account for almost all infestations of cannabis

Spider mites congregating on a cannabis plant.

Broad mites, Russet Mites and Two-Spotted Spider Mites

They range from difficult to impossible to spot without magnification and reproduce rapidly. This means, with the smaller species particularly, the damage is what you see first and by then there are already multiple generations of mites inhabiting and destroying your plant. It’s more or less impossible to control a full-blown mite population bloom, so it’s especially crucial to maintain preventative conditions and regularly inspect plants so action can be taken as early as possible if mites do appear.

When it comes to greenhouse grows the primary source of mites is infected clones, so in addition to proper sanitation, great care must be taken when sourcing new genetics. Biocontrol of a mite infestation needs to be established before flowering, otherwise the reduced light times will cause a clustering response in the mites, rendering predatory mites all but useless. If mites are detected early enough, before too much damage has been done to the affected plants, their numbers can be effectively thinned by spraying plants with water, but additional control methods are required to fully eliminate them.

Broad Mites

Broad mite. Photo by W. Cranshaw, CSU, Bugwood.org

Actual size 0.1-0.2mm

How common are broad mites and what do they look like?

The broad mite or, Polyphagotarsonemus Latus, is a new pest in cannabis gardens and sightings are becoming more common.

The most notable thing about the broad mite’s appearance is its diminutive size. They are so small that a 60x loop or stronger is recommended to properly identify them. With the naked eye you will only notice a large infestation, clusters of egg sites and the telltale broad mite damage.

Up close the broad mite has a structure and appearance similar to larger mite species. Its coloration can vary, but often it looks like a pale yellow or clear dewdrop with tiny legs.

Broad mite. Photo by W. Cranshaw, CSU, Bugwood.org

Broad mites have a large cephelathorax, two pairs of small front legs, one pair in the middle of its body, and a wispy pair of back legs; which are more pronounced in the smaller males. Under a microscope they have a medium-size head with a definitive mandible structure. Broad mite eggs are translucent, round and with white spots. These are actually tuffs of spine-like hair, but appear as spots. They are 0.08mm in diameter.

Broad mites: How to look for them and what they do to the cannabis plant

Broad mite. Photo by W. Cranshaw, CSU, Bugwood.org

Broad mites lay eggs on the undersides of leaves. They prefer newer growth and the crevices of the cannabis plants. Always inspect the damaged growth areas with magnification, paying close attention to the ribbing of the veins on the underside of the leaves.

Broad mites cause two types of damage that are great clues for identifying them. The first is often “stipling,” which is a pattern of yellow dots on the leaves. These are the tiny feeding sites from the infestation. Often stipling is inconspicuous, but the leaves turn darker. As time passes after the initial wounding the sites become yellow to gray or even necrotic. These yellow speckled leaves as well as a twisting and/or yellowing of new growth are the second signs of damage. This is a result of the mites feeding. If you see these two signs in a garden, use a 60x loop to look for broad mites.

Mites are vectors for infections, but their main damage is the sucking out of nutrients from the plants’ leaves, which interferes with photosynthesis. Draining liquids and nutrients from the leaves slows down the plants’ growth. This, along with vectors they can carry, and excrement and secretions lead to telltale damage in new growth.

How to prevent, control and target Broad mites

Neoseiulus Californicus from Biotactics

Ways to prevention Broad mites

Prevention of broad mites can be tricky. It’s difficult to surmise where they came from in many instances. Often they come in the wind, infected plant material, or are deposited by animals. One of the most likely sources of infection is importing infected clones. For this reason, many growers start plants only from seed. A good integrated pest management program is always recommended. A periodic spray with an herbal pesticide is a good start.

Ways to target Broad mites

To target Spider Mites, Clover Mites, Broad Mites and Cyclamen Mites, Neoseiulus Californicus from Biotactics, is a hearty and effective Type II predator that will lay one egg for every 4-6 units of food (spider mite adult/ nymph/ egg). Effective on almost every plant from roses to strawberries to cannabis and alfalfa.

Ways to control Broad mites

• Citric acid • Herbal oils: • Cinnamon • Clove • Peppermint • Rosemary • Thyme

Other ways to control Broad mites

A product called Nuke Em produced by flying skull is effective at eradicating broad mites. It contains potassium sorbate and yeasts.

Debug, a product described in aphid treatment and control, can be used to combat broad mites. Neem oil can be effective, but this concentrated formulation is much more effective.

Azamax and other azadirachtin-concentrated amendments are also effective and allowed in most regulated states.

Russet mites

Russet mite. Photo by W. Cranshaw, CSU, Bugwood.org

Aculops cannabicola first appeared in Serbia and Hungary in the 1960s. This cannabis specific mite is still not common but is spreading quickly through the country.

What do Russet mites look like?

They are smaller than conventional spider mites but larger than the broad mite so a 30x or larger magnification may be necessary to fully identify an infestation. They are built slightly differently than the spider or broad mites as well. Having an elongated body, often described as carrot shaped. They have a clear to milky color makes them almost look like the larvae of some other pest. Russet mites have only four legs instead of eight like other mites.

Where Russet mites are found and what they do to the cannabis plant

Russet mite damage on cannabis plant. Russet mite. Photo by W. Cranshaw, CSU, Bugwood.org

Like the other mites, they will be located on the undersides of leaves. Russet mites work their way up plants, preferring the younger soft terminal leaves, so they are found on leaves just above damaged leaves and stems.

Russet mites suck precious sap and nutrients from the leaves and petioles of the plant. This causes a type of stippling that often turns orange or yellow “russet- ing.” Soon the infected leaves die and drop off from the damage. As the colony progresses up the plant it inevitably weakens and dies.

All mite populations have the potential to increase numbers quickly when environmental conditions are favorable. For the three species of mites listed here that mostly pertains to rises in temperature. As air temperature reaches favorable conditions for cannabis growth, it also increases the mites’ rates of metabolism and reproduction. A space that peaks at 85°F decreases the mites’ time to sexual maturity as well as their gestation time. They do not multiply quickly compared to other mites.

Sometimes a clean-out and a replacement crop is better than fighting them as they multiply logarithmically.

How to prevent, target and control Russet mites

Russet mites in various stages of growth. Photo by W. Cranshaw, CSU, Bugwood.org

Ways to prevent and target Russet mites

• Inspect clones entering the garden.

• Quarantine plants for several weeks before introducing them to the nursery. Sometimes mites can lay dormant for a bit or colonies can be so small they go unnoticed.

• Never take clones from plants that have been infected even if they have been treated and seem fine. This can serve to minimize the spread of these very tiny and hard-to-control mites.

• Have predatory mites present. Amblyseius swirskii and Amblyseius cucumeris are two predators that will prevent high populations of russet mites.

• Maintaining a tidy garden and observing clean gardening habits won’t protect you from this particular pest as it is mostly introduced. There are large concerns over the future of this now international traveler and commercial hemp crops worldwide.

Ways to control Russet mites

To treat Spider Mites and Russet Mites, apply Galendromus Occidentalis during the vegetative bloom stage. This Western Predatory mite can withstand hot arid summers and can be applied with crop dusters and drones for precise application.

The russet mite works its way up plants from the bottom. So remove damaged leaves. Quarantine and treat the infected plant.

The damage mites can cause in a hot grow room can easily be so substantial during the first three weeks of flowering that starting over in a clean room with new plants maybe an economically better option. Russet mites have been reported to be particularly resistant to neem and other horticultural oils so this throw-’em-out and start over mentality may prove doubly in order instead of a pitched chemical battle.

In hemp fields the introduction of predatory mites can prove effective. Using biological control measures outdoors can have its issues, but if it’s timed right and multiple applications of predatory mites are used in intervals of four to seven days, the damage can be minimized enough to have a successful yield. Russet mites remove cell content from the leaves with piercing, sucking mouth parts.

Azadiractin Citric acid

Herbal oils: Cinnamon, Clove, Geranium, Peppermint, Rosemary, Thyme Potassium salts of fatty acids

Sulfur: Micronized sulfur applied as directed.

Spider Mites

Spider mite. Photo by Biotactics.

Actual size: .02” • 0.5 mm

How common are Spider mites and what do they look like?

Spider mites are very common. They are the most serious pests in the cannabis garden.

Spider mites are barely visible with the naked eye since they are only 0.06 inch (1.5 mm) long. They are arachnids (relatives of spiders), and like other arachnids, they have four pairs of legs and no antennae. Like spiders, they have two body segments. Their colors range from red, brown and black to yellow and green de- pending on the species and the time of year. Spider mites are so tiny though that most of these details are visible only with a magnifier. Spider mites make silk, hence the name spider mite.

The two-spotted spider mite, the spider mite most likely to attack cannabis gardens, has two dark spots visible on its back when it is an adult.

How to spot Spider mites and what they do to the cannabis plant

Cannabis plant sick with spider mites. Photo by Kristen Angelo.

They live on the plants, mostly on the underside the leaves, but can be found on the buds. They can also be found moving along their silvery webbing, from leaf to leaf and even plant to plant.

Spider mites pierce the surface of the leaves and then suck the liquids from cells. These punctures appear on the leaves as tiny yellow/brown spots surrounded by yellowing leaf.

Identify infestation by tiny spots on the leaves. They can be seen as colored dots on the leaf undersides. As the population grows they produce webbing that the mites use as a protective shield from predators, a nursery for their eggs and a pedestrian bridge between branches or plants.

Spider mites pierce cells and suck their liquids. They are more of a threat than most pests because of their high rate of reproduction.

Spider mites are by far the most fearsome of all plant pests. They suck plant juices, weakening the plants. Spider mites multiply quickly. They are most active in warmer climates than cold ones

Reproduction rate and life cycle: Newly hatched mites are 3:1 female: male, and each female lays up to 200 eggs, 1 to 5 per day, as an adult. This life cycle can repeat as often as every eight days in warm, dry conditions such as a grow room. Spider mites spread through human transport as well as by wind in out- door gardens.

Because of their rate of reproduction and the short time from egg to sexual maturity, a spider mite population can explode with shocking speed.

How to prevent, target and control Spider mites

Spider mite damage on cannabis. Photo by W. Cranshaw, CSU, Bugwood.org.

Ways to prevent and target Spider mites

Almost all spider mite infestations enter the garden on an infested plant, through the ventilation system or by gardeners who carry the hitchhikers into the garden. Use a fine dust filter (at least 300 microns) in the ventilation system, and never enter the grow space wearing clothing that has recently been outdoors, especially in a garden. Best practice is to keep pets out as well.

Neem oil is often used as a preventive, but always look out for webbing and for the yellow-brown spots mites leave when feeding. Infected mother plants transmit mites on their clones, so it is especially important to watch for mites in a mother room. When you spot mite symptoms take action immediately.

Growing from seed in an indoor environment is a great start to prevention in an indoor grow space.

Don’t introduce plants from other spaces or quarantine new plants for several weeks.

Ways to control Spider mites

Spider mites thrive in dry climates. Increasing humidity in the vegetative and early flowering stages can slow population increase.

• Insecticidal soap kills many of the mites, lowering the population and the damage, but does not eliminate the population.

• Pyrethrum is effective against some mite populations, but others have developed immunity to it.

Use predatory mites

There are many varieties of predator mites. Get those best suited to the environment of the garden. Apply predator mites at the earliest sign of infestation. Most predator species reproduce faster than spider mites, but if the mites get a good head start, the predator population can never catch up. Even in optimal conditions, control with predator mites is very difficult. Four effective species are Phytoseiulus persimilis, Amblyseius swirskii, Amblyseius fallacis and N. californicus.

Persimilis

Persimilis mite. Photo by Biotactics.

Persimilis is the first predatory mite ever used as a pest management product, to attack Two Spotted Spider Mites and Pacific Spider Mites in both Vegetative and Bloom State. These Type I predators only have one prey and can eat 35 food unites (a spider mite egg or adult) per day while laying 4-7 of their own eggs. They are extremely ravenous but need 70% relative humidity for their eggs to hatch, making them a great predator for hot spots with larger infestation problems. Find them at Biotactics.

Mesoseiulus Longipes

Mesoseiulus Longipes. Photo by Biotactics.

Targeting Spotted Spider Mites and Pacific Mites, Mesoseiulus Longipes is the rarest predatory mite species in the world and is perfect for high elevation growing as well as dry desert areas, and is available from Biotactics.

Neoseiulus Fallacis

Neoseiulus Fallacis. Photo by Biotactics.

Attack Spider mites, Clover Mites, Broad Mites, and Bank’s Grass Mites in the vegetative state or bloom state with Neoseiulus Fallacis, a cousin of Californicus. From Biotactics, this is hearty and aggressive predatory mite and will overwinter in the soil and cover crop in hibernation and is used on tens of thousand of acres of coastal California strawberry farms and min farms in Southern Oregon.

Here are several other predatory mites feed on spider mites

Feltiella acarisuga, the predatory spider mite fly

Stethorus punctillum. the spider mite lady beetle

Other ways to control Spider mites

• Green lacewings • Minute pirate bugs • Beauveria bassiana (beneficial fungi) • Capsaicin • Carbon dioxide • Cinnamon oil • Coriander oil • Fish oil • Garlic • Herbal oils • Horticultural oil • Insecticidal soaps • Limonene • Neem oil • Saccharopolyspora spinosa (beneficial bacteria) • Sesame oil

In warm indoor gardens, things can get out of hand quickly. If the infestation is noticed on a new crop, it may be more advantageous to cull that crop and clean the grow room with a light bleach solution. Additional measures include waiting 10 or more days and re-cleaning in case of a substantial outbreak. When treating plants, it is always advisable to remove lower leaves that contain large amounts of eggs. This along with repetitive spraying may be necessary.

Learn about how to target, control and prevent mites in your marijuana grow, and the many varieties of predator mites you can use as to control cannabis crop destroying mites.