With the critical time for slug feeding being now and over the next few weeks, we are getting more reports on slug feeding on field crops throughout Ohio.

The slugs have finally reached the size where feeding becomes very noticeable, and they will only grow larger and feed more. Thus, it is critical that growers begin their monitoring for slug injury. A concern that we have is that the cool and wet weather is resulting in crops that are not growing at a normal pace. Corn and soybean will be in a more susceptible stage of growth (that is, smaller plants) for a longer period of time. When determining the need for control, take special note of the newer leaf tissue, either the inner most leaves in the corn whorl, or the unifoliates or new first triofoliates on soybeans. If this new leaf tissue is being severely fed on, treatment is perhaps warranted.

When treating, growers only have a few choices of molluscicide baits. The first and most common are baits containing metaldehyde. There are two of these baits available, 1) Deadline MPs and 2) Orcal Snail and Slug Bait, which are similar materials that should be applied at 10 lb/acre. The other toxin also available is iron phosphate, which is in bait known as Sluggo. While this bait is a natural product and is considered “safer”, our thought is that the metaldehyde baits, when used as directed, are also very safe. Most problems with metaldehyde baits come from pets getting into open bags or from spills. When broadcast over fields, all the molluscicide baits are considered safe, including to the environment. The availability of these baits with the exception of Deadline MPs in Ohio is unknown, and can only be determined by checking with your dealers. Although we know these treatments at the suggested rates are expensive, ranging from $16-18 per acre, we would point out this is still a better option compared to the amount of damage that can result, often a significant stand reduction or a yield loss greater than 20%. And with the current prices of corn and soybean, stopping a serious slug outbreak with one of these baits will give you a good return. A point to consider: compared to the cost of transgenic traits for insect control, and some of the new fungicides for rust control or when applied for “plant health”, molluscicide baits perhaps are bargains!

Although some growers swear by the spraying of 28% N or other concoctions, our experience suggests highly variable control. It seems like that for every grower who says they work, we talk to 3-4 growers who says they do not. Although we do not recommend these sprays, growers might choose to try them. If you do, use them at night with no wind when the slugs are climbing on the plants. Check the crop prior to spraying to make sure that slugs are out of the ground and climbing on the plants. As with any type of treatment, come back in a few days to a week to determine the level of control. The best way to determine level of control with N spraying, or with molluscicide baits, is to either examine plants for slugs at dusk, or to look at the new growth, the inner most leaves in the corn whorl or the unifoliates or new first triofoliates on soybeans. Continued feeding on new leaf material implies limited control, while leaves with little feeding injury suggest good control.

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