By Kelley Tilmon, State Specialist for Field Crop Entomology; Andy Michel, Entomologist
Numerous locations in Ohio are still reporting slug problems, especially on soybeans. With late planting in many areas, the small size of both soybean and corn will lead to a greater damage potential from slugs.
Although all fields should be scouted, focus on those with a history of these pests, where weed control was less than effective, or where there’s a lot of residue left on the field.
Though we don’t have good economic thresholds for slugs in corn or soybean, the following guidelines are to help scout for their presence and intensity. Egg and adult sampling should occur until late May/early June when newly hatched juveniles, particularly damaging, are found. Juvenile slugs are quite small and care should be taken so they are not overlooked.
The most important time to sample for the smaller juvenile slugs is when defoliation is occurring. The best technique to sample juvenile slugs is to visit the field at dusk or immediately after dark (a flashlight helps). Juvenile slugs are easily found feeding on the plants or crawling over the crop residue.
In corn, it is easy to get a count of the number of slugs per individual plant. Because soybeans are usually planted in narrow rows, we find getting a count of slugs in a unit area, such as the number per square foot, is easier. Although there are various sampling procedures involving soil traps with or without beer, these traps do not sample the eggs, nor do they give a good estimate of juvenile slugs; they are more appropriate for adult slugs.
At this point, and given the forecast for warm weather, slug feeding should slow down. However, we would advise growers to inspect their fields before considering replanting fields.
There are a few treatments for slugs. The two available baits are those containing metaldehyde (Deadline MPs and others), and those with iron phosphate (Sluggo). See our slug fact sheet for more information: http://ohioline.osu.edu/factsheet/ENT-20.