Gaps in the stand are starting to show this week. Aside from the typical culprits, moist soils can promote the less often accused.
Millipedes are typically a beneficial arthropod that breaks down crop debris and decaying plant material. However, in the last few years, we’ve been seeing more direct feeding by them. What is happening? We have been planting earlier and earlier. If the weather turns cool and wet, seeds that have sat in the ground for a bit, swell up but are slow to emerge, making for tasty treats for millipedes. Corn is usually the target crop since it is the first to be planted but reports of soybean seed being fed on by millipedes have also come in this year. Unfortunately insecticide seed treatments do not control them. Warmer weather that helps get the crop up and out of the ground is really the only way to avoid this.
Slug feeding is evident this week. This moist weather has brought them out of hiding. Fields with decent amounts of crop debris harbour these pests, giving them a moist home to live in. No till soybeans and spring canola are most at risk. Though corn is also a host, it can usually grow out of the injury, as long as slug populations are not extreme. No insecticides are effective on slugs so this pest requires cultural control. Tillage is best, but for dedicated no tillers, using any device that can help to remove residue directly around the seed bed may reduce slug damage. In some cases, it may be too late to take action this spring but make note of fields with slug problems and plan to take action this fall once the crop is off.
One additional note, bean leaf beetles have started to enter soybean fields. In the fields I’ve been scouting, some plants were actually clipped off right at the base while trying to emerge. Others had the classic round holes in the leaves. Fields planted without Cruiser seed treatment should be scouted to ensure threshold is not reached. 16 beetles per foot of row during VC to V2 requires control or if clipping is found.
I had a grower call in asking about slug damage in soybeans. The symptoms he talks about are not consistant with slug feeding the way you describe it. These plants are being cut off at ground level. Is there anything other than rabbits that would do that to soybeans.
Slugs can sometimes clip the plants but I am more inclined to think it is bean leaf beetles. I have seen a few fields now where they clipped the plants off in spots instead of making holes in the leaves. If you don’t see slime trails on the soil or on the leaves of surrounding plants, then look for bean leaf beetles.