Be Ready To Watch For Early Season Pests

Planting into cool, wet soils could set crops up for problems.

Published on: Apr 25, 2011

If the die isn't cast, at least the writing is on the wall. This could be a cool, wet planting season. Whether or not it's a late season by conventional standards remains to be seen. By standards of the past two decades, the early window is already gone. However, there's still time for excellent yields.

One key will be getting good emergence and making sure the crop gets off to a good start. That means avoiding problems with insects and diseases. So early season scouting soon after planting as crops emerge could be particularly helpful this year.

Get yourself a good scouting guide to help identify what you see in the field, and determine whether you should worry about it or not. There are two very good pocket guides. One is the Purdue University Corn & Soybean Field Guide, 2011 edition. The other is the Corn, Soybean, Wheat and Alfalfa Guide issued by Ohio State University. It's Bulletin 827, and it comes in a spiral bound format. The Purdue Guide is perfect bound.

Here are two insect problems and two disease problems you might want to keep an eye on in the beginning of the season. Much may depend on whether or not your seed is treated with insecticides and fungicides, and what rate it's treated with. Become familiar with those treatments so you'll know which pests might not be affected, and might be most likely to show up.

Cold soil injury- The Purdue Guide classifies this as an early season problem, and says it's most likely to appear when soils are around 50 degrees F, or when there are wide variations in soil temperature of 20- to 30 degrees. Absence of emerged coleoptiles, corkscrewed coleoptiles and true leaves emerged from the sides of coleoptiles are the symptoms. It will take careful digging to determine this, and to distinguish it from herbicide injury. The biggest preventive is to make sure soils are above 50 degrees F at planting depth before you plant.

Seedling blight- One of several fungi could be involved. The result is poor emergence. Seedlings may emerge but become weak and pale green. Stick with high-quality seed, since the fungi can be either seed-borne or naturally occurring in the soil, and make sure soils are above 50 F when you plant.

Seed corn maggots - are more likely on fields with high organic matter. This includes fields that had green material before planting, including cover crops, plus fields where manure was spread. Cool, damp soils delay emergence and give these small, yellowish white, legless fly larvae time to work. The best way to minimize risk is to avoid planting when it's cool and wet. Some soil insecticides will control this insect, according to Ohio's Bulletin 827.

Wireworms – They are so named because the larvae that do damage are copper in cool and thin like a piece of wire. They are more likely to show up in patches where there has been residue in the past. If you know the field has a history of them, use a seed insecticide in advance. Once damage appears, the only cure is dry weather. Once soil become very warm, wireworms will retreat to deeper depths within the soil