The Broad Mite (Polyphagotarsonemus latus) is a harrowing destroyer of hundreds of plants, and Cannabis is one of them! Causing severe and lethal damage that stunts plant growth, they spread quickly on equipment, animals, people, and even air currents. Learn everything you need to know to prevent and defeat this pest. In this article, I review Broad Mite etymology and ecology. I explain the rough, stunting symptoms of Broad Mites and help you diagnose infestations. Finally, I review the various treatments for Broad Mites in order to help you prevent an infestation from occurring or eliminate an existing infestation.
Broad Mite Etymology:
The Broad Mite has a very descriptive scientific name, “Polyphagotarsonemus latus”. The genus, “Polyphagotarsonemus”, roughly translates to, “many-eater tarsonemus”, and “tarsonemus” translates to “thread-foot”, which is also represented in the family name, Tarsonemidae. Tarson is the name given to the last segment on the insect’s leg. Thread-footed mites have a long “thread” or “nemus” on their “foot” or “tarson”, hence “tarsonemus”.
Broad Mite Ecology:
The natural ecology of Broad Mites is poorly understood for the same reasons as many other pests: they were highly prolific before modern scientific documentation and their miniscule size has made them extremely hard to evaluate until recent developments in genomics and advanced microscopy. Most members of the Tarsonemidae, in general, are not considered pestiferous and feed on non-vascular plants tissues, making both the diet and damage of the broad mite unique in comparison to its close relatives. Broad Mites are common globally and are especially common in field and ornamental crops.
Symptoms of Broad Mites:
As the name might suggest, this species is both broadly distributed and broadly voracious, feeding on many cultivated and uncultivated plants. Broad mite infestations create crinkled, stunted leaf growth that resemble patterns of a similarly destructive mite, the Hemp Russet Mite. The Cyclamen Mite is another relative of the Broad Mite that is also extremely common and shares overlapping territory with the Broad Mite.
For reasons such as these, it is always imperative to identify the causal pest whenever possible. Broad Mites are incredibly common in agriculture globally, so proper biosecurity measures must be in place in order to look for the signs and symptoms of infestation, both in Cannabis plants as well as any nearby plants that may harbor the mites.
While the Hemp Russet Mite, a relative of the Broad Mite, has a slowly moving elongated, worm-like body, the Broad Mite is football-shaped and moves much more quickly. Males often pick up females using their special, threaded feet (hence the common family name), which are very conspicuous and easy to identify. Broad Mites also produce eggs with many small, tube-like structures, called tubercles, which appear like small dots on the surface when viewed under magnification.
Treatments for Broad Mites:
If Broad Mite infestations occur during vegetative production, there are several options for control. One such option is the use of micronized sulfur, which is miticidal, insecticidal, and even fungicidal. Incorporating micronized sulfur into a treatment plan requires the consideration of non-targets, like biocontrol agents, that may be negatively affected.
Horticultural oils are also an available option for treatment of Broad Mites during the plant’s vegetative state. Once flowering has begun, many chemical options are no longer viable.
Biocontrol agents, like predatory mites, are effective as long as the correct species are applied rapidly and at the right concentration, which is usually achievable in most residential spaces. My favorite prophylactics for treating Broad Mites and several other pests, such as: the Hemp Russet Mite, Western Flower Thrips, and Silverleaf Whitefly, are the Swirkii Mite (Amblyseius swirskii) and Cucumeris Mite (Neoseiulus cucumeris). Both the Swirkii Mite and the Cucuermis Mite can subsist on pollen in the absence of prey, making them possible to establish continuously through the incorporation of banker plants or obtained plant pollen if applied regularly. You need to be careful when selecting which pollen to incorporate, however, as some species of plants can be toxic to these mites while also providing a food source for unwanted pests like the Western Flower Thrip.
Broad Mite presence that goes undiagnosed for even a single day can cause catastrophic losses, especially in late flower. Despite innate plant defenses, Broad Mites are unabated and can retard floral production to come while damaging preexisting floral production. In situations where prophylactic measures are not active, quick assessment of presence and utilization of treatments is essential for success because the mites can quickly spread and cause irreversible damage when feeding. Carefully removing colonized tissue or whole plants can reduce the spread significantly and make overall successful treatment of the cultivation space more likely. Keeping new Cannabis plants quarantined and limiting exposure of the current crop to the environment also helps to mitigate the chance for colonization. Importantly, Broad Mites are known to be phoretic – meaning that they use other organisms for transportation. One example is the Silverleaf Whitefly. Broad Mites are attracted to the wax the Whiteflies produce and will latch onto their bodies for hours at a time. For this reason, the prevention of the Silverleaf Whitefly is also a part of the overall prevention of Broad Mites.
Integrated Pest Management Guide
Integrated pest management is a multilayered, holistic system of techniques utilized to mitigate pest presence through preventative and active treatment. In my Zenthanol Guide for Integrated Pest Management, I cover the dynamics of integrated pest management through this perspective in order to help cultivators attain the best biosecurity measures possible for their cultivation context.
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