Farming Magazine - December, 2009


Forages: Ordering Seed Corn for 2010

By Everett D. Thomas

Ordering seed corn used to be pretty simple: Order a few hybrids of the appropriate maturity and, come the following May, fill up the planter and go to it. Times have changed. Now, you need to carefully consider what genetically modified traits you need, at the same time avoiding spending your hard-earned money for traits you don’t need.

Why order genetically modified seed corn at all? Two reasons: First, traits provide protection against the most harmful insect pests—primarily corn rootworms here in the northeastern U.S.—and are effective, more so than most soil insecticides. Second, it’s getting increasingly difficult to find untraited seed of some hybrids. Some of the hottest new hybrids are only available with one or more genetic traits. In 2009, 85 percent of the corn planted in the U.S. had at least one genetically modified trait providing some combination of herbicide tolerance and insect resistance. It sure doesn’t look like this percentage will be coming down; genetically modified crops are here to stay.

Volunteer corn can cause problems

A New York farmer discovered the problems that can occur when not enough attention is given to genetic traits. He planted Roundup Ready (glyphosate resistant) corn in 2008, and when he combined his corn, some kernels were left on the soil surface—a not uncommon occurrence (With each ear containing hundreds of kernels, it doesn’t take many dropped ears per acre to add up to a potential problem.). Tillage is all it takes to put these kernels into the germination zone, as he unfortunately discovered in spring 2009 when a whole lot of them started popping up in his recently planted corn fields. However, his 2009 corn was also glyphosate resistant, so there was absolutely no herbicide he could use to kill the volunteer corn without also killing the corn he’d planted.

Volunteer corn is often more than a few plants here and there. A few volunteer plants are annoying, while a lot can be a disaster. Some years ago we had a very wet fall in northern New York that resulted in farmers having a hard time getting their corn harvested. One farmer combined his corn much later than normal, leaving a lot of lodged plants in fields. His mistake was using minimum tillage prior to the next crop, which placed a high percentage of the corn kernels in the top few inches of soil, a.k.a. the germination zone. He planted corn in these fields, and the volunteer corn came up right along with the seed he’d just planted. He had a solid stand of corn across his fields, and the only way to find the corn he planted was to look for the dark green strips left by the nitrogen in the starter fertilizer band. The farmer planted about 25,000 seeds per acre but his actual plant population was in the hundreds of thousands! The only way he was able to get any type of crop was to aggressively cultivate as close to the planted rows as possible, but he still wound up with something that more resembled forage sorghum than well-eared corn.

Think before you order

If you harvest corn for grain and encounter lodging due to weather or insect problems, a lot of mature corn kernels may be left in the field following harvest. Or, a wet fall could result in greatly delayed silage harvest and some lodged plants bearing mature ears. If either of these occurs and you’ve planted a glyphosate-resistant hybrid, plan ahead to deal with potential problems. Volunteer corn shouldn’t be a significant problem for most farmers harvesting corn for silage, since there’s not usually much lodging and the immature kernels aren’t nearly as likely to germinate. If for some reason you do have the combination of mature glyphosate-resistant corn and a significant amount of lodging, moldboard plowing the field would be the best way to bury the maximum percentage of kernels.

Don’t try to control what you don’t have and aren’t likely to get

With the increasing availability of insect-resistant corn hybrids, often at what may seem like bargain prices, the temptation may be to buy all “triple- stack” or “quad-stack” hybrids so you don’t have to worry about what gets planted where. (Triple-stack hybrids have three genetically modified traits while quad stack hybrids have four. Soon farmers will be planting hybrids with six or more traits.)

This may sound like a good idea, except for two problems. First, you’ll almost certainly be spending money for traits you don’t need, such as rootworm resistance on first-year (and in many cases) second-year cornfields. Second, and in the long run a more serious problem: Entomologists are convinced that continuous use of insect-resistant hybrids will increase the chances of developing insects that are resistant to the trait. For instance, perhaps only one corn rootworm in a million may be resistant to the rootworm trait. The problem occurs when that rootworm finds and mates with another that’s also “one in a million.”

Far-fetched? Not hardly. Based on laboratory studies, unless proper safeguards are taken, it’s possible for a Bt-resistant strain of corn rootworms to develop in as little as five years. Corn hybrids are now becoming available with more than one genetic “event” for insect control, which should greatly reduce the possibility of resistant insect strains. However, we already have four methods of controlling corn rootworms that if used judiciously will prevent this problem entirely: Granular soil insecticides, company-applied insecticide seed treatments, genetic control and don’t forget one of the oldest and most effective—crop rotation.

Now is the time to make decisions on traits

Seed dealers are out and about, taking orders and offering discounts on early orders and early payment plans. Before placing your seed corn order, go through your list of fields that will be in corn in 2010. You shouldn’t need any control for corn rootworms in first year corn, and maybe not in second year corn either—the need for control in year two varies between farms and regions. By year three, however, chances of a moderate to serious corn rootworm problem will have increased and some preventative steps should be taken: Either a soil insecticide, the highest rate of seed treatment (Cruiser Extreme 1250 or Poncho 1250) or genetically resistant hybrids.

“One size fits all” doesn’t fit this situation, does it?

Ev Thomas has worked as an agronomist in New York for 42 years, first with Cornell University Cooperative Extension, then with the William H. Miner Agricultural Research Institute in Chazy, N.Y., including managing its 680-acre crop operation. He continues to work part-time for Miner Institute and is now an agronomist at Oak Point Agronomics. He has a written our Forage column for over 10 years and has been an expert contributor on a number of other topics. Comment or question? Visit and join in the discussions.