Rain, Cloudy Days, And Low Temperatures May Cause Slug Outbreaks In Field Crops

DR. RAUL T. VILLANUEVA, DR. FELIPE BATISTA AND DR. ZENAIDA VITORIA

LEXINGTON, KENTUCKY

During the last two weeks, Kentucky has experienced sporadic but intense rains, high relative humidity, cloudy mornings, and low temperatures from dusk to dawn. These environmental conditions are favorable for the development of slugs in corn and soybeans. In addition, no-tillage practices, abundant organic residue from the previous growing season, and the presence of cover crops also contribute to favorable conditions for slug activity.

Last week (05/13/25), Colby Guffey, County Extension Agent for Agriculture and Natural Resources in Clinton County, reported an outbreak of slugs in a commercial soybean field (Figure 1) with an average of 23 slugs per 5 square feet. A study was established in this field. He also reported some damage to corn (Figure 2). During the same week, another field in Henderson County was reported with slug damage. Farmers, consultants, and scouts need to be vigilant in this situation.

Damage

Soybeans

Slugs and snails primarily affect the early growth stages of soybeans (VE, VC, or V1). Soybean plants at these stages will not recover if both the cotyledons and the apical bud are completely consumed. This damage may result in reduced planting density or the appearance of empty spots in rows. Soybean plants at the V2 stage or older are more resilient and can tolerate substantial foliar loss. These plants will recover if the feeding is partial and the leaves or stems are not completely destroyed.

Corn

In corn, if the apical meristem remains undamaged, the plants can recover from foliar injury caused by slugs. Slug damage on corn is typically observed as scraping and holes in the leaves, often accompanied by visible slime trails. This damage can resemble the injury caused by flea beetles.

Management

If outbreaks occur, slug injury to seedlings can reduce plant stands, leading to economic losses in soybeans or corn. Since there are no effective rescue treatments, replanting may be necessary. However, this decision should be based on plant population density losses in the field, the timing of the damage, and expected yield potential.

If slugs are contributing to reduced plant populations, the use of molluscicides may be required to prevent further damage. To manage slug and snail populations in corn and soybeans, Table 1 lists the products currently registered for use in Kentucky. Metaldehyde-based pellets are effective molluscicides for managing these pests in field crops; however, they can be costly.   ∆

DR. RAUL T. VILLANUEVA, DR. FELIPE BATISTA AND DR. ZENAIDA VITORIA: University of Kentucky