Fall is a Great Time to Assess Fields for Slugs

It was a great summer.  Even though some fields didn’t see a lot of moisture, many had just enough to keep slugs going for most of the season.  I often found slugs on soybean or dry bean plants even during the middle of summer.  And now with all of the corn scouting we have been doing this month,  I am frequently finding slug’s slime trails on the corn ears!  This tells me that the slug population has thrived this summer and that slug prone fields should be scouting this fall to know what to expect for fall wheat planting or next spring’s planting season.

Slugs that are present this fall will also be the same ones that overwinter and start up again in the spring in that same field.  So knowing what the slug population is like in each field in the fall will indicate what will be present in the spring.  Higher-risk fields include fields with considerable crop residue including no-till corn, soybeans and canola, wheat fields underseeded with red clover, newly
seeded alfalfa and fields following forages, especially grasses.

Fall scouting for slugs is not that labor intensive.  If scouting during the day, look for shiney silver trails left on the soil or plant surface as a result of their mucous trails.  To determine population levels take small pieces of plywood (approximately 2-3 feet long) or roofing shingles and position them on the soil surface in fields that have been harvested. 10 to 15 boards randomly scattered across the field will provide a good indication of population levels. These boards will act as shelters for the slugs. Visit the boards every 5 days for about a month, counting the number of slugs present under the boards. Morning is the best time to look since slugs will still be hanging out in their shelters.

If slugs are commonly found under monitored boards described above, that field should be considered at high risk for slug injury.  In these high risk fields, planting into conditions that help the crop grow quickly can avoid heavy slug damage.  Any form of tillage that helps remove the crop residue that slugs hide and live in can help. Even moving trash away from the seed bed can help to reduce feeding damage.  If this fall continues to be cool and moist, expect more feeding than usual.