Critical Life Events




Seasonal slug development and effects from weather (temperature and wind):

Monitor twice a week, if possible, as populations can increase rapidly and crop damage may result. The more you inspect, the more slug shelters you set up, the more accurate feeling you will have for slug activity. Identify the slug “hot spots” in your field.

(Dec-Feb) Winter. Slugs are not active when night temperatures dip at or are below freezing. Typically it is too cold (< 34°F) and too wet to treat a field this time of year. Heavy winter rains following bait application can lead to control failure because of reduced residual action and slugs are immobile. The adult stage and some eggs overwinter in the PNW. If a freeze occurs, it takes 4-5 days until slugs will become active again. Baiting for juveniles and adults at the right time in the Fall reduces egg laying, so less spring activity.

(Sep-Nov) Fall. Following a sufficient rain or irrigation, soil moisture increases will increase slug activity as they return back to ground surface feeding after a dry hot summer. Slug activity is stimulated by falling temperatures and increased moisture. Slug numbers are highest in October and November. Fall is a good time to treat for slugs when there is a window of opportunity, optimum weather and ground activity. Baiting in Fall reduces the 1st egg load so less spring activity-may need two applications. Adult slugs will mate and lay egg, until optimum slug weather declines. Typically, egg-laying after mid-October results in little to no hatching until the following spring.

(Mar-Jun) Spring. Adults become active after cold winter months pass and proceed to lay the majority of their eggs. Tiny neonates begin hatching in spring. Neonates do not feed on baits, they are primarily algal and fungus-feeders, however they will also readily feed on plants. Egg-laying ends in late May. Many neonates and juveniles feed in the spring. It is difficult for machinery to enter a wet and saturated field in the spring to treat for slugs, and rains can reduce effectiveness of baiting. However, when conditions are favorable, treat with small pellets for juveniles.

(Jul-Aug) Summer. Slugs become less active on surface as soil temperatures rise (> 70°F) and moisture falls. Slug have the ability to aestivate (rest) for several months by hiding under residue, traveling deep in soil cracks, vole or earthworm burrows. If you treat in summer to reduce slug numbers before fall-planting, choose a date when dewpoint is high at ground level.

Nightcrawlers. Nightcrawlers are capable of reducing baits by 20% during mid-November to mid-May. Using baits when an abundance of earthworms are present only protected 25% of new seedlings.