Cold Backwards Spring Ideal for Soil Pests

Tracey Baute - Field Crop Entomologist/OMAFRA Ridgetown
23 May 2008

With corn and a bit soybean seed sitting in the ground over the last few weeks thanks to the cold wet weather, some critters are likely to take advantage of this and feed on the swollen seeds. Unfortunately this feeding won't be obvious until the crop finally emerges out of the ground and plants are missing. Poncho and Cruiser treated seed will give protection against some of the critters but not all. And not all soybeans planted this early have been treated with Cruiser this year.

Seedcorn maggots love early planting and wet soils. High risk fields are those with cover crops recently plowed under, fields with manure applied or heavy weed pressures just prior to planting and those fields planted to deep. Fortunately Poncho and Cruiser seed treatments work very well on seedcorn maggot so only those fields not treated with these are at risk. Any fields requiring replanting should consider planting them with insecticide seed treatment.

Figure 1. Seed corn maggot injury

Millipedes are also likely to be feeding. These are typically beneficial critters that break down organic matter but in a cool wet spring when the seeds start to swell and not germinate quickly its just more organic matter for them to feed on. And unfortunately in this situation Poncho and Cruiser seed treatments do not control them. There are no treatments available for millipedes so the only recommendation we can make at this time is that in replant situations, wait to plant in good field conditions when the soil is warm and the seed can grow quickly out of the ground.

Figure 2. Corn Seedling damage from millipedes

And finally slugs are apt to be active too. They love the wet weather which keeps them moist. No till fields with heavy residue are at risk. Any fields still waiting to be planted that have a history of slugs should consider removing as much residue as possible from along the seedbed. Baits are available but are extremely expensive and only recommended for use in small problem areas of the field.

Figure 3. Slugs feeding on soybean plant