In Oregon, there are around 10 species of pest slugs (all of which are exotic, invasive species).
Biology and life cycle
Most active in October, November, and late February to May, depending on moisture and temperature
Generally not feeding December through early February (bait may be less effective during these times)
Feeding on weeds, seeds, lichens, fungi, decaying vegetation, and other organic materials in Christmas tree fields
Mating and egg laying occurs during active periods:
Eggs are about 1 to 6 mm (1∕25 to 1⁄4") in diameter, round or oval, transparent, golden, or white (depending on the species).
Eggs hatch after 2 to 4 weeks; those laid in October often overwinter until February.
Possibility of overlapping generations
Scouting and Monitoring
Look in weedy areas of the field.
Scout around trees in the field in the evenings, early morning, or at night.
Look in moist, protected areas during the day. Place pieces of plywood (2' × 2' or 3' × 3') in weedy areas and lift to find sheltering slugs; monitor population trends. (See Overview of Trapping and Monitoring Options.)
Trap and scout after light rains and when night temperatures are above 50°F (10°C).
Scout more actively during mild, wet winters or wet springs.
Look at interior of tree.
Check in weedy areas of field, fencerows, etc.
Monitor more intensively during wet periods.
Some trading partners, such as Hawaii and Japan, have zero tolerance for slugs.
Remove weeds wherever possible.
Place bait in the spring and fall, when moisture is present and temperatures are above 50°F (10°C). Always review current label before use.
Apply bait every 10 to 14 days when slugs are active; reapply if mold forms. Scout for slug mortality.
Apply bait in growing and handling areas the year prior to harvest; apply following a spring rain.
Apply bait evenly to the ground; do not pile bait.
Encourage and conserve slug predators, such as ground beetles, by avoiding broad-spectrum insecticides.