Tarsonemid mites including cyclamen mite and broad mite can cause serious damage to a wide range of greenhouse crops such as New Guinea impatiens, garden impatiens, dahlias, gerbera, ivy, lantana, snapdragon, verbena, zinnia, peppers and other vegetable plants.
Broad mites use piercing mouthparts to feed on the epidermis of young leaves, causing leaf-margins to curl and become brittle, puckered, and shriveled. Broad mites inject a toxin from their saliva as they feed. Their feeding causes twisted, hardened and distorted growth in the terminal of the plant and bronzed, rough, under leaf surfaces. Young terminal buds can be killed and leaves turn downward. The bud petioles are bronzed and roughened. Growers sometimes confuse leaf distortion caused by thrips feeding or plant growth regulators with damage caused by broad mites.
Broad and cyclamen mites are very small and are best seen with a 15 - 20x handlens or microscope. Broad mite eggs are covered by small whitish bumps that look like a row of diamonds. Cyclamen mite eggs are elliptical and smooth and about half the size of an adult female cyclamen mite. Looking closely you may be able to see males carrying females around, which might be confused with predation. The males apparently account for much of the dispersal of a broad mite population in their frenzy to carry the female (in-active immature) larvae to new leaves. There are also reports of the broad mite using insect hosts, specifically some whiteflies species, to move from plant to plant. Regular inspection of crops for their feeding damage is the best way to detect infestations. If characteristic symptoms are seen, send samples to the diagnostic laboratory where they can be inspected under a microscope.
Tarsonemid mites can be easily spread to healthy plants by workers and infested hanging plants can infest plants below. During scouting and other tasks, enter mite-infested areas last.
Not all miticides are labeled for broad mites. Translaminar miticides such as abamectin (Avid, Lucid, Abamectin and other generics), spiromesifen (Judo) and chlorfenapyr (Pylon) tend to be more effective than contact miticides, especially if leaf canopies are dense or coverage on the undersides of leaves is difficult. The Judo (spiromesifen) label recommends not spraying impatiens species (including New Guineas). Pylon is labeled for vegetable plants. Be sure to follow label precautions for crop safety. See the New England Floriculture Guide for additional miticides.
Note that the effects of their feeding may persist long after the mites have been eradicated.
Predatory mites, Neoseiulus (=Amblyseius) cucumeris, N. californicus and A. swirskii have been used to suppress broad mites on certain greenhouse-grown crops including vegetables (greenhouse peppers). It is important to apply predatory mites early in the crop production cycle before broad and cyclamen mites become established.
Leanne Pundt, UConn Extension and Tina Smith, UMass Extension
Photos of broad mite and damage on various crops
Cyclamen Mites and Broad Mites on Greenhouse Crops (UConn Extension)
Broad Mites and Cyclamen Mites (UMass Extension)
BioControl for Broad Mites (Greenhouse Canada)
New England Floriculture Guide (three ways to order):