Symphylans

Symphylans are very active arthropods found in damp soils rich in organic matter.They are closely related to centipedes and millipedes, so are not insects.They are often confused with springtails, but symphylans are larger, have more legs, move faster, and do not jump.They tend to be found in moist soils. Symphylans are general feeders and may attack many vegetable and ornamental crops. Garden symphylans injure germinating seeds and seedlings in particular, and they can be a serious problem on African violets when the pots are placed in moist sand or soil on the bench.

Damage

These animals normally feed on algae, fungi, and decaying organic matter in the soil and usually are no more than a nuisance. However, any stage of sym-phylan may feed on sprouting seeds or plant roots.They prefer to eat root hairs or chew holes in larger roots and crowns.This causes wilting and a blue discoloration, and also encourages infection by disease organisms. Infested plants are stunted and do not respond to fertilization.

Description and life cycle

Symphylans are slender, white or translucent myriapods, 1/4-3/8 inch (6-8 mm) long with 15 body segments, 12 pairs of legs, and long antennae. Females deposit clusters of up to 20 eggs in the soil.They hatch in about 10 days. At hatching the immatures have only 10 segments and six pairs of legs. Each time the symphylan molts it adds a pair of legs until it has 12 pairs.The immatures reach maturity in 3-6 months under greenhouse conditions, and the adults may live for 4 or more years. Populations increase fastest at about 75°F.

Monitoring

Examine the soil where infestations are suspected. Symphylans tend to run away from the light when disturbed and escape quickly into the soil, so observe carefully. Start control measures when you find 10 or more symphylans on a single root system. Symphylans in greenhouses tend to be more abundant and destructive during the fall and winter.

Natural enemies

Several natural enemies attack garden symphylans, including predatory mites, beetle larvae, centipedes, and diseases, but none has been used effectively in greenhouses.

Predators

Lamyctes spp. These centipedes are small, reddish-brown and asexual. In one experiment, five adult centipedes each in 4-inch pots quickly cut a symphylan population of 40 adults per pot in half, and greatly reduced symphylan injury to the plants.The centipedes do not feed on plants, even in the absence of prey.These and other centipedes, including Lithobius forficatus and L. bilabiatus,have also been reported as predators of symphylans but are not available commercially.

Pergamasus quisquiliarum. This preda-ceous mite was observed feeding on symphylans in the field in Corvallis, Oregon. In laboratory experiments each mite consumed an average of seven symphylans during their 12-day development. Each adult female laid an average of 33 eggs and consumed an average of 14 symphylans, although they ate more at higher pest populations. P.quisquilarum has not been investigated for use in greenhouses and is not commercially available.

Pathogens

Several pathogens infect garden symphylans and may cause up to 90% mortality under optimal conditions. Neither of the best pathogens—Entomophthora coronata and Metarhizium anisopliae— has been developed for control of symphylans or other pests in greenhouses.

Nematodes, such as Steinernema car-pocapsae, will invade and kill active symphylans within 24 hours.Their use in controlling symphylans in greenhouses has not been specifically investigated. (See "Fungus Gnats and Shore Flies" or "Weevils"for more information on nematodes.)

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