Recently, AMVAC published some joint research that showed the synergistic effects of soil insecticides and Bt traits.

I included this in my recipe for High Yield Corn because I have seen these results myself. Other growers I have talked to have seen similar results. Let’s take a look at why this works and maybe that will lead to explaining the yield bump.

For Bt to work the bug has to take a bite out of the plant. Certainly, one bite won’t kill a plant. But if you have a million rootworm larvae and you control 90% of them you still have two problems. Number one, you have a million bites out of your roots and secondly you still have 100,000 that are growing bigger. The soil insecticides kill the bug before it takes a bite out of the roots – thus reducing the feeding. I would say that rootworm feeding on a corn plant is much like a mosquito bite for humans. I like using insecticides to kill mosquitoes because even a few bites are uncomfortable.

When we compare the spectrum of insects controlled, both control many of the same bugs. There are a few more on the insecticide label. Both have unwanted side effects. Bt traits have open sores where the bug bit, and that becomes a site for disease to enter. Insecticides can be lethal to a plant if a certain post herbicide is sprayed. I do believe the benefits of using both far out weigh the negatives.

Here is a quote from that article.

Notably, 74 percent of the trials showed a yield increase. Yield increases of greater than 10 bushels/acre were observed in 40 percent of trials and greater than 15 bushels/acres in 27 percent of the trials.

That’s a bold statement but it does have some basis. When looking for high yields everything we can do to protect that yield is huge. Meaning 1% more grain on 150 bu is less than 1% more on 300 bu.

If you have a farm that maybe isn’t performing like you think it should, it may be from secondary pests and bigger than thought numbers of rootworm. It wouldn’t hurt to throw some insecticide in the boxes if you have them. Even if it’s just for one or two rounds in every field for a test strip. You might be pleasantly surprised.

SOURCE: Dave Hoy, CCA
Sales Agronomist, Great Lakes Hybrids