Tarsonemid mites

These very small mites infest a wide range of host plants, and because they are so small their damage can become extensive before the population is recognized. Preferred hosts of the cyclamen mite include African violet, azalea, cyclamen, fuchsia, geranium, ivy, and snapdragon. Broad mite is an important pest of gerbera, and may also be found on other hosts including cyclamen, geranium, hibiscus, impatiens, ivy, and peperomia, as well as vegetable bedding plants such as bean, pepper, and tomato.These mites cause problems in cool, moist conditions, unlike spider mites, which thrive in a warm and dry environment.

Damage

Specific symptoms depend on the plant species.They range from leaf distortion, stunting, and bronzing to plant death. Damage often resembles pesticide injury or nutritional problems. However, unlike those abiotic causes,the distribution of mite damage within a greenhouse is patchy. Cyclamen mite infestations first distort young leaves, which become rough and wrinkled. Later this results in stunted growth and a dwarfed appearance. Damaged gerbera leaves have bronzed areas along the midribs. Flowers on infested plants may be distorted or may not open. Shoots of plants infested with broad mite appear open, distorted, shrivelled, and burned. Broad mites feeding on the underside of young foliage of gerbera cause the leaves to become rigid and curl downward. Infested tissue on other plants becomes brown and distorted, and small leaves and flowers may fall off. Fruit on tomato, cucumber, peppers, or eggplant may be russetted or distorted.

Description and life cycle

The adult cyclamen mite is semitransparent and pinkish orange, while the immature stages are translucent. Broad mite adults are straw-colored with a prominent white stripe down the center of the back.The adults of both species are very small—less than V100 inch (0.3 mm) long.The life cycles of different tarsonemid mites are similar.Their white, opaque, ovoid eggs are laid singly. Cyclamen mites lay their eggs on upper leaf surfaces, while broad mites usually lay eggs on leaf undersides or dark, moist places on plants. In 2-7 days, whitish larvae hatch from the eggs.They develop for 1-4 days, then pass through an inactive nymphal stage before molting into adults. Broad mites can produce a generation in 10 days; cyclamen mites require 18 days. Relative humidity around 80%, low light, and moderate temperatures around 61°F favor the increase of both mites.

Monitoring

Frequent visual inspection of symptomatic plant parts is the best method for detecting infestations.Tarsonemid mites avoid light, prefer high relative humidity, and tend to be found in the crown of their host, between the densely packed young leaves of the leaf bud. Cyclamen mite is usually found within buds, whereas broad mite tends to be on more exposed surfaces. It may be necessary to use a low-power microscope to confirm the presence of these tiny mites.

Natural enemies

No parasites or pathogens provide effective control of tarsonemid mites. A few species of predatory mites feed on cyclamen or broad mites.

Predators

Euseius (=Amblyseius) stipulatus. This phytoseiid mite is a predator of citrus red mite, Panonychus citri, and feeds on broad mite in greenhouses as well as outdoors on avocado, chili pepper, citrus, coffee, cotton, mango, tea, and tomato. It consumes all stages of prey except nymphs, and will also feed on pollen and honeydew.This mite does not reproduce at relative humidities below 50%, nor at very high temperatures. It is not available commercially.

Neoseiulus (=Amblyseius) cucumeris.

This commercially available phytoseiid mite is used mainly for controlling thrips, but it will also feed on cyclamen mite on strawberry. However, it is not recommended for cyclamen mite control in greenhouses.

Possibilities for effective biological control

Although some predatory mites will feed on broad or cyclamen mite, little research has been conducted on techniques for using these predators in greenhouses.

0 0

Post a comment