Slugs II

• Slugs I

 

Biology

Slugs are legless, soft-bodied invertebrates that glide along on a trail of secreted mucus. Their tell-tale trails appear as dry silvery, meandering pathways in the daylight. Their trails may cover soil, leaves, and fruit. The marsh slug is the common species infesting strawberries in Manitoba. This light-brown to dark-grey slug is about 15 mm long when fully grown.

Symptoms of Damage

Slugs can be a serious problem in wet areas of a non-irrigated field, throughout an irrigated field, and during lengthy periods of wet weather. Slugs are most damaging to young plants but will attack strawberry plants at any stage of their growth. Besides the direct yield losses due to slug feeding damage on plants, indirect loss can also occur because of the contamination of fruit by slug faeces and slug "slime". Such cosmetic damage can render strawberries unacceptable for human consumption. Most pickers will not pick or will quickly discard any damaged berries or berries with slugs on them.

Monitoring

Signs of a slug infestation include split and shredded leaves and slime trails. When populations are high, the slugs can usually be found resting or hiding under loose soils, plant debris, or straw.

Economic Thresholds

Careful examination of an area will give a good estimate of slug density. Although no action threshold is available for slugs, 50 or more slugs per m² indicates a badly-infested field. Most growers take action if any slugs are observed.

Comments

Slug problems can be minimized through good crop management practices. Avoid over-irrigation of the crops. Avoid planting in areas that are perennially wet spots. Use rotovation at renovation time (rather than minimum tillage) to reduce crop refuse and straw build-up on the soil surface in fields prone to slug infestations. Use cultivated soil borders around the margins of strawberry fields to minimize the inward movement of slugs. Crop rotation does not seem to be a practical solution to slug management because most species of slugs feed on a wide variety of plants. Thoroughly clean equipment used in a slug-infested field to prevent the introduction of eggs or slugs into your other fields. Manage adjacent shelterbelts to minimize slug habitats. Remove low shrub and weed growth to reduce the amount of thick organic litter on the soil surface of shelterbelts.

For further information, contact your GO representative.