Known as Tetranychidae in the scientific world, and simply Spider Mites to cannabis and hemp farmers, these common crop destroying pests seem to come with the job description. There are many subspecies of spider mites, and our focus today is on the Two-Spotted Spider Mite. Some of the unique species of spider mite are much more easily identified than others; however, it is generally unwise to try, as their control measures, damage and biology are all the same.
Identification & Life Cycle
Spider mite populations WILL proliferate under the right conditions. Unfortunately, these conditions exist in many indoor grows - basically, warm with very little wind. Infestation damage can be identified by the telltale sign of the webbing they produce on your cannabis/hemp fan leaves. Inspecting for spider mites has become a daily chore for many grower teams. What your team needs to understand is that by the time you see webbing, it may be too late to control the population.
The four life stages of Spider Mites:
The species females lay between 50-100 eggs throughout their lives with unfertilized eggs hatching as males and fertilized eggs hatching as females. Spider Mites often begin to hatch their eggs within 72 hours.
The length of a spider mite's life cycle depends specifically on their environmental conditions, with the ideal temperature being the major contributing factor. An entire spider mite generation can be completed in under a week if all conditions are favorable for rapid growth.
How Spider Mites Damage Your Plants
Spider Mites damage plant leaf matter by ingesting juices from the fan leaves. Additional signs of spider mite damage are curled up and "burned" leaf edges, as well as leaves that have taken on a silky leather-ish texture. The silky webbing is predominant when mite populations have boomed within your grow.
Clean your cultivation environment, focusing on all of the little cracks and crevices indoor farmers sometimes miss. We start with washing all surfaces of the cultivation area and inspect ALL plants for spider mite presence, webbing, or damage before planting.
You can also minimize mite damage and reproduction rates by reducing water and nutrient stress as much as possible. If you are growing outdoors, hyper-focus on your cultivation area and help your plants through hot spells, which will help control spider mite populations.
The Best Method: Organic Biological Controls
This is ideal for spider mite control during your cannabis/hemp flowering cycle. Learn to introduce beneficial mites as a proactive measure after knocking down larger spider mite populations for continued monitoring and successful eradication.
Predatory Mites are an effective organic biological control for use against the two-spotted spider mite. These natural enemies do not injure plants, feed on other insects, or bite human beings. Once released, these predatory mites will immediately begin searching for water and a food source on the underside of your cannabis/hemp leaves. Your biological control measures of a small to medium infestation should occur naturally within three to four weeks.
As a farmer dealing with massive outbreaks in a commercial facility, a second release is usually required to stay aggressive with organic eradication methods. On severely infected plants, silk webbing and feeding marks will be visible. You must reduce the pest infestation before releasing your predatory mites. Consider spraying with organic insecticidal soap, BUT ONLY if your cannabis or hemp plants are still in the vegetative growth stage.
Here’s a rough guide for how many predatory mites you will need to control a given infestation:
• 1-2 per Infected Fan Leaf
• 20-30 per Medium-Sized Plant
• 2,000 per 700+ Square Feet
Well Known Spider Mite Predators (Effective for Cannabis & Hemp Issues):
Well Known Spider Mite Destroyers (MOST Effective for Cannabis & Hemp Issues):
When the right proactive steps are taken, controlling and eliminating spider mites using biological methods is not difficult. It just takes some careful observation and attention to your plants, and knowing the right predatory mites to use. In this way, you can avoid using any toxic chemicals and/ or ruining the flavor of your crop.
So, perhaps you have successfully battled spider mites and feel your integrated pest management skillset has improved since eradicating them. Well buckle up, because russet mites are, if you can believe it, an even harder pest to get rid of. They are another almost invisible, microscopic mite that destroys cannabis and hemp plants.
Russet mites are some of the most unbelievably damaging and challenging to eradicate pests affecting cannabis and hemp growers today. Tough to locate and quick to reproduce, russet mites do not produce the noticeable webbing that identifies other common pest issues like spider mites. Their miniature size allows them to attach to new areas on clothing, in removed debris, and even on other pest insects like aphids and whiteflies, allowing them to easily hitchhike into an indoor grow. This is another reason why keeping your grow room santitized from OUTSIDE contaminants is so important (but inside, you want it to be teaming with life - the right kind of life).
Understanding & Detecting Russet Mites
Russet mites lay bright, transparent, round eggs in the spring. Following the egg's hatching, these mites go through two developmental nymph stages, which resemble adults. Breeding and life cycle time varies from 8-15 days based on room design and environmental conditions. Adults are tiny and wedge-shaped, appearing copper colored. Russet mites appear differently than many other mite species in that they only have two pairs of legs.
Russet mites, similar to broad mites, measure about 0.17mm in length. These mites tend to dwell on lower parts of the plant, gradually working their way up, feeding off the lower leaves and foliage first. Russet mites feed off the sap from the cannabis plant. This, in turn, stunts the plant's growth during veg, affecting its ability to grow more abundant flowers come harvest time. But they don’t stop at the foliage; russet mites are particularly attracted to flower resin, meaning they will often attack cannabis buds - aka, your money. All of this will slowly rob the plant of its vital nutrients. This is why many new farmers think they have a plant deficiency they cannot fix, because the symptoms of russet mites look like a deficiency. Over time, russet mite feeding has a severe impact on bud and flower production throughout a grow, making preventative control and early treatment the most economically viable treatment methods. Females overwinter inside the stems of affected cannabis plants as well!
More specifically, symptoms of russet mites are commonly yellowing leaves (chlorosis) and leaf curl ("taco-ing"), as well as stunted and slow growth, signs which are often mistaken for a pure nutrient or water deficiency. Cannabis fan and sugar leaves affected by these mites might appear glossy or wet-looking, while buds will begin to brown and eventually die. If unseen or left unchecked, russet mites will continue to spread and reproduce, ultimately sapping an entire plant.
correctly identify whether there are russet mites. Remember, as I mentioned before, the symptoms of a mite infestation are similar to nutrient deficiencies or pH imbalances. Therefore, you will want to make sure you're 100% certain you're dealing with russet mites before starting a treatment.
Once you've identified russet mites on your cannabis plants, it's now time to try and treat them so you can save as many plants as possible. Although there is really not much you can do about a late-stage infestation, there are a few different treatment methods for dealing with russet mites if they are caught early enough.
Treatments for Russet Mites
As far as we know, there are no really effective biological controls for russet mites. If you catch them early enough, there are some natural, organic insecticides that will be effective at combating them. If your crop manages to survive a russet mite infestation, we recommend you sterilize your entire grow afterwards, and start over with new soil.
Insecticidal plant soaps are great for identified trouble areas that need spot-treating. And you should do this IMMEDIATELY after you’ve identified an infestation. These soaps are ideal for use on smaller russet mite infestations as well as a possible LAST MINUTE attempt on early flowering cannabis plants. Be cautious, and make sure to avoid getting the soap on your buds. Consider using this simple method multiple times for the best possible results.
Here are a few other organic insecticides that may be effective against russet mites.
When it comes to eradicating heavily infested cannabis gardens, it's always better to prevent than treat. Therefore, always make sure your cannabis plants are growing in a pleasant environment with excellent ventilation and proper air circulation coming from a variety of areas across the room. If you’re growing indoors, be very careful about introducing “foreign contaminants,” i.e. unintentionally bringing in biology from outside. Please remember to always inspect your cannabis plants DAILY and act quickly as soon as you see any signs of plant stress. Obviously, Russet Mite infestations are much easier to handle when caught and identified early on.
About the Author
Daniel Enking is the founder of Everflux Technologies. He is a life-long environmentalist and practical dreamer who is obsessed with resource efficiency and imaged an "everything recycling machine" at age 10.