Slugs and millipedes like the rain
Editor’s note: This article is from the archives of the MSU Crop Advisory Team
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With the recent rains, slugs are common in some fields. Slugs feed on cotyledons, stems and leaves of emerging plants by scraping the leaf surface. With heavy damage, leaves take on a tattered appearance. Wet conditions favor slug populations, thus no-and reduced till fields with residue are at greater risk for slug feeding, especially if plants are emerging and growing slowly. Slugs are hidden during the day, but silvery slime trails may visible. To check for slugs, move residue aside during the day or walk fields at night. Another trick is to put something flat (like old shingles) out in the field overnight, by daybreak, slugs often accumulate on the underside. Seed treatments do not control slugs. Baits containing metaldehyde are very effective, but expensive. Drying conditions and good crop growth are the best solution to a slug problem.
Phil Kaatz from Lapeer County visited a wireworm-damaged field this week, only to find millipedes as the true culprit (view photo). This is a rare, but increasing find, in parts of Ontario, Indiana and Michigan. A few years ago, several wet fields near the Tittabawassee River in Saginaw County lost stand due to millipede feeding. In all cases, the affected fields are wet and have a lot of crop residue. Millipedes are normally beneficial, feeding on decaying plant material, but under unusual conditions they can damage seeds and emerging plants. Millipedes are distinguished from other long, brown insects (such as wireworms) by being “leggy,” with four legs on each body segment. “Milli” means a thousand in Latin, and “ped” means foot, thus literally “a thousand-feet.” Millipedes are not insects, and seed treatments do not seem to impact them. As with slugs, drying conditions and good crop growth are the solution to overcoming a millipede infestation.