HOW TO SPOT A RUSSET MITE INFESTATION
Many cannabis growers may not realize they have a russet mite infestation and it isn’t unusual for them to confuse the symptoms for other problems such as heat damage, overwatering, or nutrient deficiency, as well as pollen, mold, or the tobacco mosaic virus.
Because russet mites are so tiny and elusive, you often won’t see them until you have a full infestation. In big enough numbers they may appear as a beige or yellow mass, with symptoms often more prominent towards the tops of the cannabis plants. There is also noticeable drooping and curling of leaf edges. Where mites live inside plant tissue, the leaves and stems are usually dull-colored.
Damage on leaves and shoots caused by russet mites.
The brown or yellow spots caused by russet mites are often mistaken for mold, fungus or pollen. An intense russet mite infestation on cannabis plants can also be difficult to diagnose because it’s hard to see the individual bugs. Russet mites can reproduce and attack cannabis plants all year round and are most harmful in the flowering stage when buds get infested.
BIOLOGY AND LIFE CYCLE OF RUSSET MITES
Russet mites are among the most understudied bugs in marijuana plants. Females are about 170-210 microns, slightly bigger than their male counterparts which measure 160-165 microns. To emphasize how small russet mites are, that’s just about twice the width of human hair!
Russet mites are pale in color, oblong-shaped, and have only two pairs of legs. They are easily distinguishable from other pest mites because of the lack of webbing. Due to their very small size, russet mites can only travel short distances which explains they aren’t likely to move off the host plant. However, they can be carried by wind in outdoor settings or air currents in enclosed grow spaces. Contamination is also possible via human hands and clothing.
It is believed that russet mites have a life cycle similar to that of other eriophyoid mites. Depending on environmental conditions, these mites can complete their life cycle in as short as 7-10 days or as long as 30 days.
Eggs hatch a couple of days after they are laid and larvae emerge three days later.
Larvae then molt into two immature nymph stages—protonymph and deutonymph—before becoming adult russet mites. Females survive up to three weeks and lay anywhere from 10-50 eggs in their lifetime.