We are receiving numerous reports right now about slugs causing significant feeding injury requiring treatment with baits. These reports are two to four weeks early compared with most years, and is a result of the warmer winter and March. Slugs have attached out earlier than normal and have reached a size that causes noticeable feeding injury much sooner. We addressed this possibility in C.O.R.N. Issue 8, April 10, when we wrote: "Warmer weather and soil temperatures will be causing slugs to hatch earlier and will result in slugs beginning their heavier feeding earlier. If planting times are normal, slugs will be a bigger and larger threat than normal. If planting early, perhaps the slug feeding will be more similar to normal conditions. If planting is late, slugs will be relatively larger and capable of even heavier feeding."
Corn and soybeans present two different concerns. With corn’s growing point being below the soil for a few weeks, most of the feeding above ground will be to growing leaves that will be replaced, and not on the growing tip that would kill the plant. Because of continued growth of corn that will probably occur, there is some leeway in terms of the time required to make the treatment if needed. But keep in mind that the corn is still relatively much smaller than when feeding normally would be occurring, and thus, presenting a much more serious situation.
However, the growing point of soybeans is between the cotelydons as they emerge from the soil. Thus, the slug is easily able to reach and feed on both the cotelydons along with that growing point, making it much easier for slugs to kill the soybean plant as it emerges from the soil. This fact makes immediate treatment of soybeans perhaps more critical if no leaves have yet emerged and expanded.
For farmers who have experienced slug issues in the past, it is critical that fields be scouted now. If plants have emerged and have leaves, look for the telltale signs of leaf feeding. But for soybeans not yet or just now emerging, or yet to be planted, care should be taken to determine if slugs are present and lying in wait. This latter situation could require a bait application just prior to emergence. Use your own past experiences with soybean stand reductions caused by slugs to determine whether an early treatment should be made this year.
The two available baits are those containing metaldehyde (Deadline MPs and others), and those with iron phosphate (Sluggo). See our slug fact sheet for more information (pdf).