Get Rid of Broad Mites With Jorge Cervantes
Oregonians love to grow high-grade cannabis – craft farmers know this means extra attention to the girls in the garden. With the advent of legalization, we are gearing for full-scale recreational sales, but there are problems that need solutions.
One of the recent dilemmas brought to light was off-label pesticide use. There are no FDA-approved products for pest control when it comes to cannabis. The reason for this is, of course, federal prohibition. There have been no long-term impact studies on consumption of cannabis grown using various products that horticulturists utilize during cultivation. This means that we have no idea what these products may or may not contribute to our health while we medicate. The state of Oregon has gone as far as to send a letter stating, among other things, “pesticide applications that do not follow the pesticide product label pose risks to public health and safety and are a violation of state and federal law. The label is the law.”
Following this USPS-delivered warning, Oregon growers from large-scale producers to hobbyists are wondering what to do about pests. The past few years in Oregon has shown a consistent increase in the realm of invisible scourges – specifically the broad mite. It seems that a large share of growers have faced or are currently dealing with these little monsters. All manner of pesticides are being applied, some in combinations on schedules in an attempt to salvage the crop. Commonly used products individually and in mixtures are Eagle20 (myclobutanil), FloraMite (spiromesifen) and Avid (abamectin). Each is made by Dow, Bayer or Syngenta, and approved for use on ornamental shrubbery. They are all considered toxic to humans in some capacity.
Jorge, you have taught people how to properly and efficiently grow cannabis. Enthusiasts, many of them our very own readers, look up to you as a “weed guru,” looking to your literature for answers to many garden problems. We’d like to hear your thoughts on broad mites, and how to diagnose, treat and cure an infestation.
1. What exactly is a broad mite and how are they different than an average spider mite?
Spider mites are much larger than broad mites, hemp russet mites or cyclamen mites. Spider mites are most common indoors.
Broad mites and cyclamen mites cause similar damage. Broad mites are about 0.1 millimeter (mm) long with eight legs. Larvae have six legs and are hungry at hatch. Broad mites reproduce prolifically between 70-80º F. They hatch in two-to-three days and each female can produce 40-50 eggs. Cyclamen mites are about 0.2 mm long. Larvae hatch hungry and have four pairs of legs with a waxy body. They have very similar reproductive cycles as broad mites.
Both broad mites and cyclamen mites secrete and inject a toxic growth regulator into plants as they feed. The toxin and feeding by mites deforms foliage and distorts growth. Leaf edges tend to cup up or down, become brittle and show signs of scarring. Intermodal growth is stunted and overall growth is underdeveloped. New growth can blacken and die. The damage resembles herbicide damage or it could also be confused with a viral disease or micronutrient deficiency.
The worst part is that most growers do not catch the damage until the little mites have infested all the plants in the garden. I was at a garden recently that was completely infested, 24 huge 10-foot-tall plants. The mites were so bad that none of the flowering females had any white stigmas in their flowers.
Hemp russet mites are hard to control if they get started in the garden. The 0.2 mm-long mites have two pairs of legs on beige bodies. No webbing distinguishes them from other mites. At 80º F, russet mites have a 30-day life cycle.
They feed on foliage, including petioles, meristems and leaves. Leaf edges curl yellow and die. Foliage becomes brittle and becomes beige with mites when infested. Russet mites feed on stigmas rendering them sterile. They eat resin glands, too. This can diminish harvest potency substantially.
2. How is a broad mite infestation diagnosed? What are the main symptoms a grower should look for?
Initially leaves will start to curl up slightly, and the entire plant will lose its vibrant green color. Leaves generally curl near the base at the petiole. New growth is stunted and weak. Broad mites inject a toxic growth hormone into the plant that slows and distorts growth. The toxins persist for a time after the mites are dead. The problem is usually confused with a micronutrient deficiency or pH imbalance. But if you look closely you will see more consistent signs of damage.
Super small broad mites are difficult to identify without a 60-100x microscope. Once you have sight of them in the microscope, they are easy to identify because they move relatively quickly. Without positive identification, control is difficult.
3. In your experience, when treating broad mites, what has worked and what has not worked for you?
Personally, I have had no problems with broad mites, hemp russet mites or cyclamen mites. I use Aerated Activated Compost Tea (AACT) that I explain below
I was at a friend´s house when visiting Portland. Paul Stanford, who organizes https://hempstalk.org/site/, had a crop of 24 big 10-foot-tall plants. They looked great at a distance, but looking closer, the buds don’t have any white stigmas popping out of the seed bracts. The broad mites had done away with them all.
We looked at the leaves closely. Cupped upward near the base, all the new little flower buds were just little nubs, with no white female stigmas. I thought the crop would be lost, or at best they could get half as much harvest. That was on August 26, 2015. About a month or so later, I spoke with Paul on the telephone; his crop is fine, with lots of fuzzy white female stigmas and healthy growth.
4. What organic treatment options are available? During vegetative cycle? Flower?
My favorite prophylactic measure is to spray with aerated activated compost tea (AACT). This stuff is great. You mix in a bit of compost, chicken manure, base of microbes and biological life with water and add oxygen. Make the mix in a 30-gallon container filled with 20 gallons of water and mix. Add an air pump to increase oxygen content of water and let it rip for 24-48 hours.
Apply the mix directly and heavily to foliage with a hose-end sprayer or pump-up sprayer and soak the ground as well. The biological life in the mix will coat and out-compete any and all intruders.
Look on the Internet for AACT. Vital Landscaping in Grass Valley, Calif., is helpful with a great supply. Applications can continue through flowering, but remember that the plants should be rinsed at harvest. A rinse will remove dirt, disease and pest residues on the surface of the plant. I like to rinse buds with dilute hydrogen peroxide (H202) at harvest. I mix up a dilute, 5% solution of H2O2 and water in a large shallow container. Then, harvesting 12- to 24-inch-long branches, I dip them into the mild H2O2 water for 15-30 seconds, agitating them around in the water. I remove the branches and shake them off to get rid of the big drops of water, then dry them in front of a fan for 10-30 minutes to remove the rest of the water and prevent mold.
Once we identified the problem as broad mites with the help of the Cannabis Encyclopedia at Paul Stanford´s garden, we knew what to do – find the newest biological product. We consulted Samantha Miller from Pure Analytics, and he suggested BotaniGuard. Paul called around to a few grow stores and could not find it in stock; only one garden store knew about broad mites. I found it on Amazon, Paul applied as per directions, and a few days later, the plants showed signs of new healthy growth.
5. Share with us some specific contributing factors to infestation in the garden, i.e where or how does one “get” broad mites or what attracts them to gardens?
The little bastards are everywhere. We first had them in Spain about seven, maybe eight years ago. They came in from the grape crops in the northern wine-growing regions around Barcelona, but all of these mites can come from many different crops, annual flowers and vegetables as well as perennials. Once they are in an area, you have to beware all the time. Even when you get rid of them, they may easily be in your neighbor´s garden.
6. What are some DIY preventative measures that can be implemented against these pests in the garden?
Grow organically. Grow a strong healthy garden. Build strong healthy soil. Use AACT early in the season. This compost tea will save you from many problems and the plants love it. I use it prophylactically against diseases and pests, and it works to build an organic environment in the soil as well.
7. Where in the U.S. are hot spots for broad mite activity and which are the least?
Wherever they can over-winter; warm climates are the worst. Indoors, they can be a menace because they are attracted to indoor plants. There should be a “broad mite” hotline.
8. Do you have any other recommendations for DOPE readers?
Always learn more about growing and share it with friends. Upload your garden videos to YouTube and check out my YouTube channel, https://www.youtube.com/user/jorgecervantesmj. I will upload a video about broad mites in the next few weeks and continue to upload videos. I am also on my website forum answering questions regularly at www.marijuanagrowing.com. My Internet cultivation classes are at www.THCUniversity.org and my new book, the Cannabis Encyclopedia, is out. Pay attention to chapter 24 – “Diseases and Pests” as it gives much background on, and control measures for all mites and other pests and diseases that attack cannabis.