Broad mites (Polyphagotarsonemus latus) and Cyclamen mites (Stenotarsonemus pallidus ) are very similar in life cycle and damage they cause, so they are together in this section. First they are distinguished then symptoms and control measures are lumped together.
What is a Broad Mite?
The broad mite, Polyphagotarsonemus latus (Acari: Tarsonemidae), are a microscopic species of mite found on many species of plants, including important agricultural species. Broad mites are also currently affecting cannabis plants, as the industry matures with legalization. The mites are found in many areas throughout the world and are major pests in greenhouses.
What is a Cyclamen Mite?
This is one of the smaller mites that attacks cannabis crops. The adult female mite is yellowish brown, 250 to 260µ long, with hind legs reduced to slender threadlike structures. The male is approximately 75% the size of the female. On the adult males the fourth pair of legs is modified and used to transport the pupae or adult females.
Identification (Broad Mites): Aggressive adult mites are microscopic, about 0.1 mm long with 8 legs. Larvae have 6 legs and are hungry at hatch. They are less than half the size of the red spider mite. Soft-bodied nymphs move fast. Color is translucent white and yellowish and other light tones. The 0.08 mm long eggs have a series of about 30 whitish bumps, an oval shape with protruding circular surface and stick hard to the leaves. The adult has a dark dorsal band. Each female can produce 40-50 eggs in a lifetime. They hatch in 2-3 days with an appetite. After eating 2-3 days they start the pupal stage en-route to adulthood. Broad mites reproduce most prolifically at temperatures between 70-80º F (21-27º C).
Cyclamen Mites: are less than 0.2 mm long and range from colorless to green or brownish. The waxy looking mites have four pairs of legs. Cyclamen mites share many characteristics with broad mites. Male cyclamen mites have a very strong claw mounted at the end of each fourth leg. These mites avoid light and prefer high humidity and cool 60º F (15º C) temperatures. They can hide inside buds, under leaves and any protected place on foliage. Eggs are smooth and hatch in around 11 days when deposited in dark moist locations.
Damage: Mites secrete a plant growth regulator or toxin as they feed. And a few mites can cause a lot of damage fast. Feeding damage deforms and distorts young buds and leaves. Leaf edges can curl up or entire leaves can cup down, pucker, crinkle, become brittle and show signs of scarring. Internodes shorten, growing tips are stunted and overall growth is underdeveloped. New growth can blacken and die. Damage resembles herbicide damage. And can also be confused with viral disease, micronutrient deficiency, or herbicide injury. Damage may appear for weeks after the mites have been controlled. Damage is usually not detected until significant damage is incurred. Damaged foliage will not recover. A microscope will be necessary to detect the actual mites; a hand-held loop is not powerful enough to see them.
Cause: Microscopic or micro-mites are able to walk short distances and are dispersed long distances by wind or by attaching themselves to a people, tools or a winged insect (aphid, whitefly, etc.) and hitching a ride. Male mites actually transport eggs to new foliage. They migrate to cannabis from many plants including but not limited to, houseplants, African violets, cylacmen, begonias, snapdragons, impatiens, gerbera, snapdragons, fuschia, daisy, azelia, ivy, camellias, jasmine, lantana, marigolds, grapes and vegetable hosts – beet, beans, cucumber, eggplant, pepper, potato and tomato plants. They are also a common greenhouse pest in some crops.
Prevention: Cyclamen mites can’t take temperatures above 92º F (33ºC) but the spider mite will, if you drop the humidity to 30% they can’t develop into adults. But with the conditions in most garden rooms are perfect for them to thrive. Do not let broad mites enter the garden room or greenhouse. They are more difficult to prevent and thrive in hot conditions. Use certified pest free growing mediums. Keep the garden room very clean. Wear clean clothes and shoes into the garden room and greenhouse. Do not grow ornamental or food plants that attract cyclamen or broad mites. It is important to eliminate them before flowering because plants cannot recuperate if they go into flowering with broad mite damage.
Control: Biological: Locally occurring mite predators give satisfactory control in many areas. Two natural enemies – Euseius stipulatus and Typhlonomus ovalis are being evaluated as bio-control agents of these mites. Amblyseius californicus eats red spider mites and also P. latus. If there is no food for the predator they leave or die. A. californicus can also eat pollen to maintain themselves. The strawberry, ricinus comunis L. and margaritas (genebra) are some of the food with pollen.
Treatment: They are not susceptible to some dinitrophenol compounds and synthetic pyrethroids. Submerging plants completely in a miticide dip is very effective to treat small plants. Some chemicals are effective including fenbutatin, diazinon, dicofol and kelthane, all very harsh chemicals and some are systemic. I do not recommend anything systemic!