There is no doubt that the cannabis industry is developing. Humans have grown this crop for many years, but only in recent years has commercial production become the focus of attention. It seems that with our years of experience, humans will know how to grow this crop without any problems, but everything from planting a few plants to commercial production will change everything. One problem that many growers find is that cannabis has many pest problems. Phylloxera, leaf aphids, thrips and fungi are just a few of the growing numbers. The most terrible problem is pests. Planting operations often cause these pests to lose crops, and understanding them is the key to controlling the problem.
To say that you have mites is a broad term. There are many types of mites in commercial production, and hemp is susceptible to several different species. It is important to correctly identify your mites so that you can use the correct control options. You cannot guess; you must be 100% sure. If you are not sure, your pest consultant can help you identify.
For prevention and control, many growers choose to use biological control agents. Due to concerns about pesticide residues on edible crops, national regulations and drug resistance management issues, biological control options are very suitable. The key is to start producing quality products as early as possible.
Common mites in cannabis crops can be divided into three families: Tetranychidae (Tetranychidae), spider mites, Tar mites (Tarsonemidae), thread mites and Eriophyidae (Eriophyidae). The list may expand over time as there are new host records.
When someone talks about spider mites, they usually refer to two spotted spider mites (Tetranychus urticae). Remember, spider mites are a broad family of mites. There are many types of spider mites, but only one is the two-spotted spider mite. This is what is common in marijuana. Tetranychus urticae is also found in many other ornamental and vegetable crops, which makes the pest difficult to control because it is ubiquitous.
Adult females are about 0.4 mm long and males are slightly smaller. Generally, they can be identified by a webbing rotating on the surface of the blade. In this net, females will deposit eggs (up to a few hundred), and these eggs are completely round.
These mites thrive in the hot and dry conditions common in greenhouses. It seems that the population exploded overnight, but often they have been building there without being noticed. When living on leaves, two spotted red spiders feed by inserting their mouthparts into plant cells and feeding on their contents. If they are controlled as early as possible, the plant can potentially recover without destroying the leaves. If the plants are not treated, the leaves will turn yellow and appear necrotic spots. Mites can also migrate into flowers and become a problem when the plants are dry when they are harvested.
Damage caused by mites (Polyphagotarsonemus latus) can cause growth and deformation. Eggs are ovoid and covered with white spots, which is the best way to identify them.
The widespread mite is another species of mite that has a wide range of host plants and is distributed worldwide. Their mites are much smaller than the two-point spider mites (to see them, you need to zoom in at least 20 times). Adult females are 0.2 mm long, while males are slightly smaller. The easiest way to identify them is from their eggs. The eggs are oval in shape with white clusters on them. They almost seem to have white spots on them.
Before damage occurs, it is difficult to detect the presence of mites. This is usually how growers find that they own them. The mite has a poisonous ointment, which causes the new leaves to distort and thicken. Even after treatment, these leaves cannot recover from this damage. The appearance of new leaves (without mites) will be normal.
This mite posed a challenge to growers in 2017. Due to poor production methods and sanitary conditions, it spread like wildfire. This mite is different from the previous two mites in that it is a host-specific host for cannabis. People have always been confused, thinking that this is the same species as the red brown mite in tomato crops, but it is another type of mite (Aculops lycopersici).
The mites are very small and require magnification to see them. Small in size, it can be easily mounted on amusement facilities that are completely unaffected by the growers’ clothes and tools. Most growers don’t know about the hazard until they see it, when the mites are at a very high level. When the mites feed on crops, they can cause bronzing, curling leaves, and in some cases blistering. Once a serious infestation occurs, it is difficult to remove this pest.
Ephedra s mites, Aculops cannabicola. The damage caused by Aculops cannabicola includes curled edges and russet leaves. Over time, the leaves will turn yellow and fall.
What these mites have in common is that you can greatly reduce the chance of infection with mites by adopting reasonable hygiene measures. It only takes a few simple, low-cost steps to stop an outbreak. Treat the growth area as you would a hospital operating room. • Restrict visitors and staff: If someone (including you) participates in another planting event, do not allow them to enter your production area without clean work clothes or changing clothes. Even then, unless it is his or her first stop today, it is best not to let anyone in. When you brush an infested plant, you may pick up mites on your clothes. If you use this kind of clothing to rub on other plants, it may spread pests and diseases. •Tools: When moving between plants and crop areas, clean tools regularly with disinfectant. • Clones or cuttings: This is the number of operations that you have unknowingly infected yourself. The pests directly reach the introduced plant material. When cutting, there should be a standard operating procedure, how to handle them to ensure a clean start. Remember, you will most likely not be able to see the problem with the naked eye at this stage. Immersion in gardening oil or insecticidal soap can greatly reduce the risk of new mites damage. When these cuttings are stuck, do not put them in the main production area with other crops. Maintain isolation to ensure that no pests are missed during the immersion process. •Pet plants: Do not try to use growing facilities to overwinter indoor plants or other pet plants for employees. Many cross-host pests will happily skip your crops. • Start immediately, don’t wait: once the drill cuttings are stuck, start them immediately in the predatory mite program (Table 1). Even the growers of ornamental plants, whose individual plant value is lower than cannabis, have begun to keep their crops clean from the beginning. Don’t wait until you encounter problems.
Some states provide approved lists of pesticides that can be used in cannabis production. Many of these products are considered the lowest risk pesticide products. This means that they are not subject to the Federal Insecticide, Fungicide and Rodenticide Act. These products have not undergone rigorous testing of EPA-registered products.
In most cases, when consumed with mites, gardening oils can provide excellent control effects, but spray coverage is essential. If the mites are missed, their numbers will increase rapidly. Likewise, once most of the oil dries, beneficial ingredients can be released.
Early active treatment is essential, especially when using biological control agents. As the hemp crop matures, trichomes will form. Once this happens, the plant will become too sticky for predators to move around on the plant. When the interest can move freely, please treat before then.
For the past 25 years, Suzanne Wainwright-Evans (protected by email) has provided professional gardening/entomological advice to the industry. She is the owner of Buglady Consulting and specializes in biological control, IPM, pesticides, biological pesticides, organics and sustainable pest management. Her crop focus includes ornamental plants, hemp, hemp and herbs/vegetables. View all author stories here.
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You are correct that garden oil is effective. Even if you do not see visible signs of phytotoxicity, paraffin oil and other petroleum-based oils tend to slow photosynthesis for several days. Essential oil sprays kill the russet mites very quickly, but they tend to strip the wax from the leaves, which also slows the growth of plants. The circadian rhythm combines vegetable oil and peppermint oil to deposit natural polyvinyl alcohol wax on the leaves to replace the wax that may be washed away. One of these waxes is a biostimulant, triethanol. If interested, I can send you some tests. The best growth stimulating effect can be achieved when applied weekly starting from rooting clones or emerging seedlings.