Editor’s note: This article is from the archives of the MSU Crop Advisory Team
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The recent wet weather across the state, combined with crop residue, creates ideal conditions for slugs. Slugs feed on cotyledons, stems, and leaves of emerging plants. No- and reduced till fields with residue are at greater risk for slug feeding. Slug baits with the active ingredient metaldehyde are registered for corn and soybeans and they are highly effective. Bait formulations (typically small pellets or granules) fall to the soil surface and draw slugs in. Unlike contact insecticides, which must be sprayed directly onto the pest critter, slugs do themselves in by moving to the toxic bait and feeding. I can tell you personally that slug baits are very effective – I treated my garden last weekend and now have a slug killing-field.
The most common metaldehyde product is Deadline MPs (MP stands for mini pellets). A low rate [10-12 lbs per acre] is adequate for field crops. To help assess the reduction in a slug population before and after baiting, I place several old shingles or boards out in the infested field and leave them overnight. Slugs like to accumulate under the flat surfaces during the day, and can be easily counted.
A count before and after baiting gives you a visual check that the treatment reduced slug numbers. Deadline is sold in a 50 lb bag at approximately $2 per pound, so a treatment runs $20 to $24 per acre.
Since plants usually grow out of slug damage once growing conditions pick up, feeding must be pretty dramatic before a $20 per acre treatment makes sense. If only a small part of a field is affected, consider limiting the treatment to this area. It is sometimes tough to find product, but in previous years Wilbur Ellis in Sparta, Helena in Watervliet, and UAP in Sunfield carried Deadline.