Cool, wet conditions have been the perfect weather to favor slug populations.  Slugs are able to eat many types of plants, and even in fields that haven’t been sown yet slugs can successfully feed on weeds. 

Late planting may cause more slug headaches than usual – as slugs get geared up, the small size of both soybean and corn will lead to a greater damage potential from them.  So particular attention should be paid to late-planted corn and soybeans.  Slugs can also damage un-germinated seed.  Thus, growers with a history of slug problems with newly planted corn or soybean should watch their crops closely over the next few weeks. 

Although all fields should be scouted, focus on those with a history of these pests, where weed control was less than effective, or with a lot of residue left on the field. 

Slugs are nocturnal so you may not catch them in the act of feeding unless you inspect plants after dusk.  If you see feeding damage on plants, sift through residue and look under stones in the field. 

An asphalt shingle laid out on the ground, painted white to keep it cooler, is also a good sampling device. 

Slugs will collect under it during the day.  We do not have research-based thresholds for slugs in field crops.  However, if the level of damage concerns you a rescue treatment may be in order.  There are few products available, but two of them are Deadline MP (metaldehyde) and products containing chelated iron.  These are formulated as baited pellets which slugs must consume, so apply them when you are not expecting rain.

Related:New modes of action sought for fighting weeds

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