In a nutshell: Very small mites, difficult to detect; wide variety of host plants; new growth feeders—cause new leaves to curl up and turn brown at the edges; mainly a greenhouse pest; viral disease vectors.
What are broad mites?
Broad mites (Polyphagotarsonemus latus) are primarily a greenhouse pest in temperate regions like Canada. Since they can’t overwinter, they don’t pose a serious problem for plants grown outdoors. Broad mites can only develop under conditions of high relative humidity (70–90%).
What kinds of plants do they attack?
These mites feed on a wide variety of plants, both vegetables and ornamentals. Peppers are especially affected, but so are eggplant, tomato and cucumber. Broad mites also attack flowers such as azalea, begonia, gerbera and cylamen.
What do they look like?
Adult broad mites, like all mites, are related to spiders and have eight legs. Being mites of the Tarsonemid family, they also have no eyes. They’re about 0.2 mm long, broad and oval-shaped, and can range in colour from pale yellow to yellow-green, depending on their last meal.
Female broad mites have a white stripe on their backs and lay their eggs on the undersides of leaves or on the fruit.
The eggs are about 0.07 mm in size, elongated, oval-shaped, translucent and speckled with white dots. They’re firmly attached to the surface on which they were laid.
The larva resembles the adult broad mite but is smaller and has only six legs. One day after hatching, the larva transforms into a dormant nymph (similar to a pupa or cocoon). One or two days later, the adult mite emerges. The male mite often carries a female nymph around to mate with her as soon as she emerges as an adult.
How do I know if my plants are under attack?
Broad mites prefer young, developing plant tissue, like growing plant tips, young leaves and flower buds. Mites usually group together on the undersides of young, expanding leaves, feeding near the leaf stalk. This causes the leaf to curl up and turn dark brown at the edges near the base, a typical sign of broad mite attack.
Mild infestations often result in brown, collapsed spots or brown stripes forming a fine network on the leaves. When the infestation is serious, this network becomes so dense that no more green tissue can be seen. In most cases, the main veins are untouched, and they stand out as a green pattern against the brown leaf. Brown, corky patches can appear on the leaf stalks and main stems, as well.
The growing tips of affected plants become misshapen, and when the infestation is severe, they can be killed. This causes plant growth to stop, and in time the whole plant dies off.
Corky patches can also appear on fruit, causing them to crack or become misshapen. Broad mites often cause flowers to become discoloured and even deformed in severe cases.
The effects of a broad mite attack can resemble a viral infection and remain visible for several weeks after the mites have been eliminated. Even relatively low mite populations can cause serious damage.
How to get rid of Broad mite
Koppert offers different solutions for biological pest control of Broad mite.