By Brian Hefty
The first time I walked in a field sprayed with Accent herbicide after Counter insecticide was applied at planting time, I was shocked. The corn looked burnt, about like severe drought stress. I had heard that could happen, but I had never seen it. That was in 1990.
When I asked the chemical manufacturers why this happened, I was told, in layman’s terms, that both Counter and Accent need to get metabolized by the plant. The problem is that they can’t both get metabolized at the same time, meaning one, the other, or both become toxic to the plant. Accent is an ALS herbicide. Counter is an organophosphate (O.P.) insecticide. Plus, Counter is very systemic in the plant. Not long after that, we were using Lorsban (O.P.) insecticide and Hornet (part of Hornet is an ALS) herbicide on our farm. I didn’t even think about it at the time, because I was told it should be safe, and it certainly appeared to be.
A few years after that, Roundup corn came out, so weed control in corn post-emerge was no longer an issue. Roundup was about all that got used, and there was no interaction with Roundup and insecticide. Several years later, rootworm Bt’s started to get released, so insecticide use dropped dramatically. Now we definitely didn’t see any issues.
Here we are 22 years after my first bad experience with Counter and Accent, and we’re worried about the problem all over again. Plus, it seems that HPPD herbicides (including Callisto, Laudis, Impact, Capreno, Balance Flexx, etc.) could have the same interaction issues with organophosphate herbicides as ALS products. Some, like Laudis, claim to have no issues according to the label and the manufacturer. Others, like Callisto, don’t recommend using O.P. insecticides in front of them.
Before I give you our suggestions, let me first say that you won’t always see an issue, even if you do the complete wrong thing. I want to also remind you that corn is $5 a bushel or more for new crop, so every bushel of yield loss could be big.
If you want to use an organophosphate insecticide (or any insecticide that contains an O.P. component) use a non-ALS, non-HPPD herbicide. O.P. insecticides include Counter, Lorsban, and Aztec. Insecticides that are NOT O.P.’s include Force and Capture LFR. ALS herbicides include SureStart and TripleFLEX (the Python in SureStart and TripleFLEX is an ALS), Hornet, Accent, Beacon, and others. I listed many of the HPPD’s above. Products that do not include HPPD or ALS include Status, Clarity, Buctril, atrazine, Harness, Surpass, Dual, Verdict, and many more. Again, even if you use an O.P. and follow with an ALS or HPPD, it may not cause issues. In fact, it may be labeled, like Laudis is. I’m just trying to give you something to think about with all this discussion.
If you decide you really want to use an ALS or HPPD herbicide, that’s fine. We would just encourage you to use a pyrethroid insecticide like Force or Capture LFR to be safe. The last thing you need this year is a herbicide-insecticide negative interaction that hurts your yield. You know that a rootworm insecticide will most likely pay if you have rootworm or other bug problems. You know that Roundup probably won’t kill all your broadleaves by itself. Just plan ahead for these things, and you should have no issues whatsoever.