Symphylan Management

SYMPHYLAN MANAGEMENT

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Garden Symphylan

If soil moisture is adequate, the garden symphylan can be observed in mint root borer or strawberry root weevil soil samples taken in the fall. However, postharvest samples for mint root borer may be too shallow to detect a significant symphylan population. In the fall, this is because of the dry soil profile, a natural seasonal reduction in population, and the symphylan's tendency to travel downward in the soil to avoid high temperatures or seek moisture.

SAMPLING

The best time of year to sample for symphylans is from March through September. However, to properly control them with an insecticide, you must apply it prior to spring regrowth. Take a soil sample to a depth of 10 inches from several different sites in the field (one site per 1 1/2 acres). Count the number of symphylans per sample and calculate an average number per sample. If an average of four to five symphylans is found in the samples, control may be required depending on the vigor of the stand.

If treatment is justified, apply Lorsban either through the sprinklers or by incorporating it by irrigation immediately after application (see the insecticide table for rates to apply). If possible, identify areas in the field where the population is concentrated and treat only those areas. Symphylans prefer heavier soils to sandy soils and often infest ridge or high areas, avoiding low spots where water concentrates.

BIOLOGICAL CONTROL

A mite predator, Pergamasus quisquiliarum, commonly occurs in western Oregon soils (Berry, 1973). The developmental period of this predator requires about 17 days, compared to about 87 days for the garden symphylan at 20oC. Therefore, this predator could complete about five generations to one generation of the symphylan at this temperature. Studies have shown that this predator may consume up to 12 symphylans during one generation, indicating that it could be an important factor in regulating symphylan populations.