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College of Food, Agricultural, and Environmental Sciences


Be Prepared For High Slug Populations This Season

February 20, 2003

WOOSTER, Ohio — Ohio no-till growers may be wrestling with high slug populations again this growing season. Ron Hammond, an Ohio State University research entomologist with the Ohio Agricultural Research and Development Center, said that fall field sampling has yielded high slug populations that could carry into spring if conditions are ideal. “We’ve done our normal fall sampling and at least for the months of October and November, we have a lot of slugs out there. It wasn’t hard to go out with the sampling tools that we used and find fields that had a lot of slugs in them,” said Hammond. “Even though we had a drought this past summer, the slugs seemed to have survived that very well. And although we’ve had some extremely cold weather the past few weeks, we’ve had a lot of snow cover too. And snow is a very good insulator. We think that going into the spring, the potential is there for a lot slugs.” Hammond said that corn and soybean fields will be sampled again in the spring to determine if high slug populations are still present. Growers should refer to the Ohio State Extension C.O.R.N. (Crop Observation and Recommendation Network) newsletter for updates. The publication can be accessed online at The juvenile stage of the slug creates the most damage to crops and its voracious appetite and large densities can be devastating for farmers who have had a history of slug problems. Upon hatching in early to mid-May, the slug will begin feeding on anything that is planted in the field, whether it’s corn, soybeans or alfalfa. Slug feeding can cause significant reductions in corn yields and total stand loss in soybeans. Growers who have had a history of slug problems should keep a close eye on their fields when the weather begins warming up. Finding two to four slugs per trap could indicate a potential problem and top priority should be given to those fields in regards to treatment options. “For soybean growers, we’ve had a lot of people who have lost their fields before they even realized they had a problem. We recommend growers monitor their fields before the soybean plant emerges. For corn growers, we recommend watching their fields after the corn crop emerges,” said Hammond. “Growers may want to consider an at-planting time treatment to protect their soybean crop if slugs are a problem in their fields. Treatments are expensive, but losing a field and having to replant is not a cheap alternative either.” Many soybean growers through northeast Ohio were forced to replant two, even three times last year due to slug damage. “Last year was the worst slug damage we’ve seen, not only due to the numbers of slugs present, but also due to late crop emergence,” said Hammond. “So a lot of those no-till fields just got hammered.” An overly wet spring delayed soybean planting well into late May and early June, coinciding with newly hatched juveniles. Hammond said that a more normal planting in early May tends to give the plants to opportunity to outgrow any slug feeding that might occur. “A lot of what’s going to happen this season will depend on the growing conditions. If growers can get their crop in the ground early enough and slugs have their normal hatching time, then perhaps we’ll see less injury,” said Hammond. “I can predict that we’ll have a lot of slugs this year, but I can’t predict the injury because there are still a lot of variables that will affect it.” Ohio State and U.S. Department of Agriculture researchers plan to conduct studies on alternative slug control methods: everything from at-planting time treatments to tillage practices that still meet no-till requirements to testing the relationship between slug populations and soil pH. “We will be conducting on-farm research and evaluations to see if we can find an inexpensive way to better manage these slugs,” said Hammond. “One of the reasons that growers don’t jump on the bandwagon with bait treatments is that they are too expensive and a lot of growers feel it’s not the best thing to use.”

Candace Pollock
Ron Hammond