Field Guide    Pest Management  Slugs

Slugs

CROPS IMPACTED: Vegetable crops, field crops

 

 

 

Family: Phylum Mollusca

About Slugs

Reproduction and Life Cycle

There are many varieties of slugs and the process of mating, laying eggs, hatching and development are not similar across species. This makes it difficult to reliably predict the outcome of a slug infestation. Typically, slugs will mate in late summer and bury their eggs in the soil over winter. Come early spring, the eggs will hatch. This time of year is usually associated with the most crop damage as juvenile slugs will ravish crops and spread to further fields. Slugs feed on a variety of weeds and vegetables crops and are most active in moist, cool weather. During high temperatures and drought, slugs will enter a dormant state.

Slugs Identification and Habitat

Identification

Slugs are essentially a snail without a shell. These grey mollusks have soft, squishy bodies and are legless. Different species can vary in color and pattern but most are earthy tones such as grey, brown or dull orange. The size of the slug varies and is greatly dependant on the climate, location and temperature. Size can range from a fraction of an inch to several inches. Slug eggs are small, gelatin-like and opaque and can generally be found clumped together under residue from crops or in the soil.

Slugs leave ragged holes on the lower leaves of crops when they feed that form a “window-pane” shape. The primary identifying characteristic of a slug is the classic slime trail residue that is left on leaves that have been fed on. In severe cases plants appear to be skeletonized and likely will not recover from the damage. As well, slugs are known to attack emerging seedlings in the same manner.

Habitat

Slugs prefer cool and moist environments and thrive in humid and overcast conditions. They are most active at night or on cloudy days in late May/June. Slugs are mostly found to feed above ground on the lower leaves of crops or below ground on residue, depending on the amount of moisture in the soil.

Slug Control Method

A slug infestation can be quite difficult to manage but there are a few tips and tricks. Cultivating fields where slug pressure is high will greatly reduce the population because tillage exposes slugs to dehydration and predation by predators. Removing weed and crop residue from the area surrounding seedlings will help to reduce damage at an early stage. If managed correctly, most plants can outgrow light feeding damage.

If necessary, zone tillage will eradicate slug habitats while maintaining the benefits of reduced tillage. Overall, weed control and removal of refuge can help to reduce the slug population over time.

Chemical Control

There are a few methods available for chemical control though it is important to consider biological options first. When spraying, the application will be most effective if applied when the slugs are active. Early morning is best, especially if the following day is predicted to be sunny as the slugs will dehydrate in the heat.

Latin / Alternative Slug Names

  • Arion
  • Deroceras
  • Helix
  • Limax

Sources

http://www.omafra.gov.on.ca/IPM/english/sweet-corn/insects/slugs.html#advanced

http://ento.psu.edu/extension/factsheets/slugs-as-pests-of-field-crops