CHAMBERSBURG, Pa. — Slugs are molluscan pests of plant life found in our gardens, fields and lawns. There are more than 20 slug species that can be found in Pennsylvanian landscapes, but four are most common in field crops: the banded slug (Arion fasciatus), dusky slug (Arion subfuscus), gray garden slug (Deroceras reticulatum) and marsh slug (Deroceras leave).
These species feed on virtually all our field crops and can cause significant damage during crop establishment and early development.
Slugs will overwinter as eggs, adults and juveniles in the residue and soils of crop fields. Eggs that overwinter hatch in early spring and thrive in cool, wet conditions. They generally do not develop in a synchronous manner — all at the same life stage during a period — making it hard to predict population trends. High populations of slugs are common in fields practicing reduced or no-till methods because heavy residues and little soil disturbance can promote conditions that support slug numbers.
Researchers at Penn State Extension have been monitoring slug populations across the state to better understand their biology and lifecycle. This season at our local research site in Lemasters, Pennsylvania we have observed high numbers of gray garden slugs causing significant injury to emerging field corn. In addition, multiple producers across the county have shared that a significant number of soybean acreage has been replanted due to stand loss from heavy gray garden slug feeding.
Unfortunately, management options for slugs are limited. Using an integrated approach that relies on several management methods is recommended. In general, here are some things that tend to limit slug populations:
Agronomics and variety selection: slug damage tends to be worse during the early stages of plant development, one tactic includes fostering early plant growth to ‘outrun’ the threat of stand loss against significant slug numbers. When possible, selecting varieties that are rated as ‘excellent’ for emergence and seedling vigor can help. In addition, planting in conditions that allow for the full closure of the seed slot can help reduce direct feeding on corn and soybean seeds.
Residue management: many growers who experience slug problems are committed to no-till or reduced tillage practices, they may consider using a more aggressive row cleaner to move residue out of the row & allow for better infiltration of sunlight to contribute to improved crop emergence. Often the removal of residue can facilitate drying the exposed soil and helps create a less favorable habitat for slug feeding.
Protect natural enemies: slugs predators include ground beetles, rove beetles, centipedes, harvestmen (daddly longlegs), firefly larvae, and spiders. Invertebrate predators of slugs can be protected by increasing crop diversity across your rotation, using cover crops, and judiciously using insecticides.
For more information on slugs as pests of field crops or to discuss management tactics please contact Brittany directly at 717-263-9226 or bac5801@psu.edu
–Brittany Clark, Penn State Extension
