Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu
Last week, I talked about slug injury on corn. Unfortunately, slugs in soybeans can be a little more difficult to manage. The reason for this is that slugs will feed on soybean before they emerge and kill the plants outright. In many cases, you don’t realize you have a slug problem until you return to a field, 7-14 days after planting, expecting to see a beautiful stand of soybeans, only to find that you have poor emergence or that you don’t have a stand at all. The classic scenario where we tend to see the greatest problem is when soybeans are no-tilled into heavy crop residue and planting conditions were a little wet and the seed slot did not get closed all the way. Slugs will travel up and down the open seed furrow, using it like a “highway”, to feed on the germinating seeds. Once the soybean plants emerge, slugs will continue to feed on the cotyledon, unifoliate, and trifoliate leaves. Above ground slug feeding injury can be confused with bean leaf beetle damage so look for slugs and “slime trails” to make sure you accurately identify the culprit.
Below ground slug feeding injury
Above ground slug feeding injury
“Slug Highway”
Tillage is the most effective cultural control method if a field has a slug infestation, especially in re-plants situations. We have limited experience with how well “slug bait” can control slugs when they are feeding on germinating plants before they emerge and if slug bait is effective at reducing damage in a re-plant situation.
Here is a report from our 2013 Delaware Soybean Board funded project: Management of Slugs in Delaware Soybean Fields. This report has more information evaluating the effectiveness of chemical control management of slugs in soybeans:
Another tactic, aside from tillage or making sure the seed furrow is closed, is to adjust your planting date. Prior to egg hatch, planting early allows the plants to emerge before heavy slug feeding injury occurs from juvenile slugs. Once the slugs hatch, delaying planting has been effective by allowing plants to rapidly emerge. In several of the fields I have been in this week, I have seen newly hatched grey garden slugs. In general, anything that will promote rapid seed germination and emergence will help to get the plants out of the ground before slugs have an opportunity to kill the plants outright.