Top genetics and the appeal of a higher return on investment are making conventional corn hybrids more appealing to farmers across the country. Before Bt traits became the norm, we had great success growing conventional hybrids. Now, as they make a resurgence in the market, it’s important to remind ourselves a bit about the insects that feed on corn. European Corn Borer (ECB) can be a serious pest if populations reach economic injury level.
The Lifecycle of the Eastern Corn Borer
ECB overwinter in their larval stage in residue of corn stalks and weed stems. Depending on the weather, larvae pupate, then emerge as adult moths in late May and early June.
ECB moths usually lay eggs (as many as 30) on the underside of corn leaves. Corn that was planted early is the most desirable place for a first generation infestation. In 5 or 6 days, the eggs develop black spots, which are the heads of the larvae. The black heads are key to treatment, because this is a clear sign that hatching is going to occur quickly.
In June and early July, when corn is around 18 inches tall, be sure scout for feeding injury in the whorl of the plant. Midrib tunneling may occur as the larvae mature, which can cause leaves to become brittle or break easily.
As the larvae reaches about half grown, it will move out of the whorl and bore into the stalk, leaving a small hole and a brownish sawdust material called frass. The larvae will develop inside the plant stalk until they pupate. Tunneling inside the plant can cause the corn to become stunted and opens the plant up to potential stalk rots and lodging later in the season. The moths emerge during late July through early August, beginning the second generation.
During late July and throughout August, moths will lay their eggs. Once hatching occurs, larvae move to leaf axils and sheaths to feed. ECB generally feed in the middle of the plant, and at the half-grown stage, larvae tunnel into the plant similar to the first generation borers, leading to stalk and tassel breakage, damaged and dropped ears and an increased potential for disease. A third generation can occur if the weather is warm enough to support development to the larval stage before winter arrives.
Check out these links from the University of Nebraska for more information on scouting for first generation and second generation ECB infestations. Specific methods vary by region, so be sure to check with your local extension office to verify the best methods for your area.
What You Can Do If You Find ECB in Your Corn Crop
Treating ECB is difficult if the insects are allowed to enter into the plant, so timely application is critical for insect suppression. If treatment is needed, there are several products which work well when applied in a timely manner. A few to consider are carbaryl (Sevin®), lambda cyhalothrin (Warrior II with Zeon Technology®), permethrin (Ambush® or Pounce®) and zeta-cypermethrin (Mustang® Maxx).
Planting conventional corn could improve your bottom line.
Just keep an eye out for pests and be ready to protect your corn if need be. In many cases, insect numbers will never reach economic injury levels, so only treat when necessary. Save that treatment money for other critical inputs.
Ambush® is a registered trademark of Zeneca Ag Products.
Mustang® Maxx and Pounce® are registered trademarks of FMC.
Sevin® is a registered trademark of Bayer.
Warrior II with Zeon Technology® is a registered trademark of a Syngenta Group Company.