Broad mites are members of the Tarsonemidae family, known as the ‘white mites’. Another member of this family that attacks cannabis is the Cyclamen mite. Both mites cause similar damage.
Broad and Cyclamen mites can move quickly, and are exceedingly small: about 200 micrometers in length, or about the thickness of a human hair or sheet of paper. Not only can these mites be hard to find, their plant damage can be difficult to diagnose. Broad and cyclamen mites only feed on young, developing leaf tissue. The saliva they inject into the plant is a growth regulator that causes deformities that oftentimes mimic nutrient deficiencies. For this reason, accurate identification and diagnosis of these mites is critical.
What to look for: New plant growth that looks distorted, twisted, or 'spindly' in appearance.
Life Cycle of Broad Mites
Broad and cyclamen mites have only 3 life stages; their life cycle is relatively short.
Egg - Broad mite eggs are covered in large tubercles, giving them the appearance of being covered in ‘jewels’. In contrast, the eggs of cyclamen mites are smooth in appearance. Larvae - The larvae have 6 legs, and actively feed. Adults - Males are smaller than females, with their body being more tapered. Adults can live up to 15 days, depending on sex and environment.
Biology of Broad Mites
- Broad mites are native to the tropics and are not subject to diapause in temperate climates.
- They thrive in warm climates, with development times accelerating as temperatures rise.
- Development time of broad mites from egg to adult at 86˚F is less than 4 days, with green bean plants as a host.
- Development time drops to 15 days at 59˚F.
- Females lay single eggs, rather than in clusters, making detection difficult, especially when viewed under magnification next to trichomes.
- Adult male broad mites can sometimes be found carrying female larvae, still in their larval cuticle. This is known as ‘pre-copulation’. Copulation then occurs once the female has finally emerged.
- Broad mites are blind, and depend on their sense of smell to maneuver and locate food sources.
I see broad mites, now what?...
There are many forms of bio-controls for broad and cyclamen mites. If you currently have a pest issues, the most effective predators that we have seen are Amblyseius andersoni, Amblyseius swirskii, and Amblyseius californicus. In many cases, 2-3 successive applications of the liter containers, packaged with active adults, will be necessary to gain control.
I don't see any broad mites, but I'd like to act preventatively....
Some of the most effective delivery methods for preventative use are sachets (breeding bags). These usually allow for predators to emerge from the sachets and on to the plants for 3-5 weeks. Californicus, andersoni, and swirskii all come in sachets.
However, factors such as the presence of other pests and the ambient temperature and humidity will help determine the best species of predator to use. Please read the brief descriptions below to determine the best option for you operation.
Additional Notes About Broad Mites
* Broad mites only feed on new growth.
* While damaged leaves and shoots can be inspected for the mites, nearby growth that is not currently showing signs should also be inspected.
Amblyseius andersoni feeds on russet mites, broad mites and two spot spider mites. They will also feed on pollen and thrips larvae, allowing the population to survive when pest mite populations decrease.
Andersoni are active and effective in both high and low temperatures (43˚-104˚F), and make an excellent choice for preventative mite control in your commercial garden.
Amblyseius swirskii is primarily known as a thripspredator that feeds on many common cannabis plants. Swirskii is ideal for warmer climates, as it is native to the Mediterranean. It feeds not only on thrips, but also broad mites and russet mites, as well as whitefly eggs.
Optimal results are seen when adults in 1 liter containers are used in conjunction with slow-release sachets. Growers have used it successfully when treating or preventing russet mites, broad mites, and thrips. Swirskii also feed on white fly eggs, and performs best in warmer temperatures.
Amblyseius californicus is a generalist predatory mite that primarily attacks spider mites, but will also feed on many other leaf inhabiting mites (even some microscopic species, like broad mites), other small insects and pollen.
Californicus is tolerant of various temperatures and lower humidity, but works best under warm to hot conditions.
Amblyseius cucumeris feeds on the larvae of several species of thrips, including the common variety: Western Flower thrips. It will also feed on broad mites, cyclamen mites, and, to a lesser extent, two spot spider mites.
Their relatively low cost makes them an attractive option against thrips in operations when temperatures are below 85˚F.