By Darren Hefty
Imagine for a minute what it was like raising corn in the 1980s and early 1990s. Times were different back then in many ways. We didn’t have Bt traits to fight corn rootworms, so farmers were using soil-applied insecticides. There were also no Roundup Ready crops, so many different modes of action were being used to kill the weeds. In fact, ALS herbicides were still about 100 percent effective on kochia and waterhemp in our area, so they were primary products for most farmers.
Since ALS herbicides and organophosphate (O.P.) insecticides like Counter (which works systemically within the plant) were commonly used, farmers were pretty aware of potential interactions between these families. The ALS products and O.P. insecticides cannot always be metabolized by the crop at the same time. Applying both in the same year may result in no damage at all, or it could result in corn that looks fairly similar to corn under severe drought stress. Needless to say, yields are dramatically reduced in that case. At $1.50/bushel corn back then, you might have taken a chance with that, but at $5+ corn today it’s a whole new risk proposition.
The reason we’re talking about this is that many farmers across the country find themselves living like they’re in the 80s and early 90s again. We’re seeing rootworm resistance to single trait corn rootworm Bt’s like VT3, so we’re right back to using insecticides at planting time. Coincidentally, weeds resistant to Roundup are becoming more widespread, and farmers are often adding a tankmix partner to their Roundup applications. Many of these products, pre and post, contain ALS herbicides. It looks a lot like the days of conventional (non-Roundup Ready) crops again. So here are the products we’re concerned about using.
Organophosphate insecticides include: Counter, Lorsban, Aztec (contains 95% O.P.), and SmartChoice (which contains Fortress). Of these, Counter is the one we worry about the most with potential herbicide interaction issues because it is the only one that is systemic, but the others have some degree of concern, as well. You can certainly read the labels of these products to see what the manufacturer’s level of risk tolerance is. I’ll just say this: if you want to use some herbicides you’re concerned may interact with an O.P. insecticide, switch your program up. The easiest thing would be to use a non-O.P. insecticide like Force (dry) or Capture LFR (liquid). Both of these choices are pyrethroids and have no known interactions with herbicides.
Speaking of herbicides, the ALS herbicide family is the one we’re most concerned about potentially interacting within your corn plants in a negative way with O.P. insecticides. ALS herbicides include SureStart and TripleFLEX (since both contain Python), Hornet, Accent, Beacon, Resolve, Basis, Permit, Steadfast, and others. In addition to the ALS herbicides, we now have a number of HPPD family herbicides that also could have some interaction with organophosphate insecticides, although a couple of the HPPD manufacturers would disagree with that. The HPPD family includes Laudis, Callisto, Impact, Armezon, Capreno, Balance Flexx, and others. Again, there could be no problem at all. Some of these products like Laudis are even labeled to follow an O.P. Then again, the choice is up to you.
The easy answer is to pick products with little to no risk. If you really want to use an O.P. insecticide (especially Counter), pick a herbicide like Status, Clarity, Buctril, atrazine, Harness, Surpass, Dual, or others that have no ALS or HPPD in them. If you really want to use an ALS or HPPD herbicide, just pick a pyrethroid insecticide like Force or Capture. As more insecticides and conventional herbicides are being used each year, it’s important to ask questions and fully understand how these products work and interact before you make decisions for your crop.
We’d rather have you play it safe than take a chance with a negative interaction between a herbicide and an insecticide that could rob your yields and your profits.