Pest description and crop damage Symphylans are not insects but represent a unique class of soil-dwelling arthropod similar in appearance to centipedes. They are white in color and are smaller than centipedes. Immatures have 6 legs, but as symphylans mature, they acquire up to 12 pairs of legs and the antennae elongate. There is just one pair of legs per segment which is similar to centipedes but different from millipedes (2 pair per segment). Garden symphylans can damage new orchard plantings if the orchard site has a history of pressure from this pest. Typically, this would occur when former grass seed or Christmas tree fields with a history of the pest are converted to hazelnut orchards. The symphylans move to the roots of newly planted hazelnut trees where they cause feeding damage. When a grass crop is sprayed out to plant a hazelnut orchard, the symphylans may aggregate at the roots of the newly planted hazelnut trees because there is no other food source. Tree damage may not be evident for some time after it has occurred, but trees that have been attacked may become symptomatic during periods of water stress when it becomes apparent that the damaged roots cannot support necessary water uptake. It is unlikely that the symphylans would actually be found during the hotter periods of the growing season as they utilize the soil profile to thermoregulate and typically go deeper when soil surfaces are too warm. The pest tends to aggregate in the upper soil profile in spring and fall when surface soil is moist and temperatures are moderate. Sampling efforts should be concentrated during these periods when the symphylans are in the upper soil strata. If there is a problem the white symphylans should be evident in the roots of establishing trees, so the problem cannot be diagnosed without digging up trees at a time when the symphylans are active. Older trees should be resistant to the pest. Symphylan "hot spots" or patches tend to recur year after year in the same areas of the field or orchard.
Pest monitoring Dig young trees when soil is moist and temperatures are moderate in the spring or fall to inspect roots for symphylans. Soil samples can be used to collect symphylans and taking cores can help estimate activity at different depths. Baits can also be used to attract symphylans for detection and monitoring. Cut a carrot or potato in half and bury it in a shallow hole carefully dug so as to not disturb the below soil structure, then cover it. After 2-5 days recover the bait to examine for presence of symphylans.
Sample for symphylans before planting the orchard, particularly if the orchard site was formerly producing grass seed or Christmas trees. Manipulation of soil structure is a management tactic. Tillage in particular can crush symphylans that are at the soil surface and may disrupt the soil porosity that the symphylans rely upon to move through the soil profile. Symphylans cannot tunnel through the soil, so they need the naturally occurring pores to move through the soil. Slight soil compaction through rolling may also help reduce soil pore connectivity and symphylan presence in the upper soil profile.
Management-chemical control: HOME USE
This pest is unlikely to be an issue for home orchards.
Management-chemical control: COMMERCIAL USE
Pesticides or fumigants are more effective when applied prior to planting. Depending on the crop present prior to planting hazelnuts, more chemical pest management options may be available. While there are chemistries that are registered for hazelnut that can be somewhat effective against garden symphylans, none are specifically labeled for garden symphylan.