Warm, Dry Winter Could Cause More Insect Pressure

Posted on March 12, 2012 by:
by Mark Grundmeier

There’s been much talk about the possible effects of a warm, dry winter on 2012 planting.  Dry, warm winter poses unique crop threats for several reasons including a lack of soil moisture, weed pressure and insects.

So what does this mean for Midwest farmers?  Bottom line, farmers need to be especially vigilant in scouting their fields this season.  It will become more important to their overall profitability if they know what’s in their fields before economic thresholds are exceeded.  That’s why today I want to talk about the insects that could be especially threatening throughout the 2012 planting/growing seasons.

Let’s begin by dividing insects into two groups:

  1. Survivors, or insects whose life cycle is directly affected by the weather patterns.
  2. Opportunists, or insects that can take advantage of weather patterns like the Midwest experienced during the winter months of 2011-2012.

Group 1 – Survivors

Corn Flea Beetles belong in the first group because the warmer-than-normal weather might allow for more of these pests to survive.  They typically overwinter in our area, and their survival rate depends on the temperatures in December, January and February.  When the mean temperatures for these three months add up to over 90 degrees Fahrenheit, then there will be a greater number of survivors that will be ready to attack corn fields in the spring.

Likewise, overwintering Bean Leaf Beetles can become an economic pest in soybeans when there is a larger-than-normal percentage of survivors.  Both types of beetles will feed directly on young plants just as soon as they emerge.  And adding to the degree of injury, both beetles have been known to infest the young seedlings with diseases while feeding on them.  Corn Flea Beetles have been known to vector Stewart’s Wilt, and Bean Leaf Beetles have been known to vector Bean Pod Mottle Virus.

Seed treatments that include an insecticide like Cruiser®, Poncho® or Gaucho® can help prevent these insects from attacking young plants and seeds.  We know seed treatments prove to be a good investment during a cold, wet spring.  Just because it looks to be a dry spring, don’t be fooled into thinking seed treatments won’t pay for themselves this season!

Group 2 – Opportunists

The second group of insects includes all species that can or will eventually feed on the crop.  If we have a dry spring and early summer, then crops may suffer moisture stress.  ANY kind of stress can be greatly enhanced by insects (or any diseases for that matter) that feed upon those plants, including, but not limited to:  Corn rootworms, corn aphids, stalk borers, European corn borer, cutworms and armyworm for corn.  In soybeans, there would be the 1st and 2nd generation Bean Leaf Beetles, soybean aphids, two-spotted spider mites, Japanese Beetles and Soybean Cyst Nematode (even though they are not an insect).

Most of the pests mentioned above can be controlled by applications of insecticides if done at the proper time; the exceptions to this are rootworms (because they are below-ground) and SCN (also below-ground and not an insect.)

More good news… the recent rain and snowfall have helped the situation although we’re not yet out of the woods.  Some timely rains in March and April can provide adequate moisture for a bountiful crop.  That’s my positive thought for the week – and I’m sticking to it!


Categories: General Agronomy