Weed, disease, and insect control in most crops is rarely overlooked. For some reason, insects in wheat seem to be an exception. Is it an attempt to save money by not spraying? Yield loss due to insect feeding and the increase in disease severity that affects plants that have been fed on is well documented and a shock to any potential profits you may be looking forward to. With low wheat prices, you need every bushel you can get in order to turn a profit.
Here’s what you need to know about insecticides for wheat. At the end, check out the action plan for this spring and summer.
Chemical Families
The two main chemical families used post-emerge are the pyrethroids and the organophosphates (OP). Pyrethroids include products like Silencer, Warrior II, and Mustang Max. They generally have around a 30-day PHI (pre-harvest interval). Pyrethroids have become the preferred products in wheat due to their safety to humans, slightly longer residual than OPs, and the fact that they don’t seem to add a whole lot of burn to certain tankmix partners that the OPs can. Oh, and the fact that a full rate only costs around $2/acre doesn’t hurt either.
OPs include Lorsban and dimethoate. They have a couple advantages versus the pyrethroids. OPs work faster, which is great when you have a heavy insect outbreak you need to stop quickly. Both Lorsban and dimethoate also have activity on mites like the brown wheat mite in some areas of the country. The PHI is similar to pyrethroids with Lorsban at 28 days and dimethoate at 35 days. While these products aren’t the most dangerous things out there for humans, the safety factor is certainly more of a concern with these OPs as compared to the pyrethroids. Speaking to the comment above about heating up tankmixes, you’ll need to watch the OPs with oil-based formulations as they can cause more leaf burn when tankmixed with anything containing the active ingredient in Buctril; 2,4-D; and with a number of the fungicides. Speak with your local agronomist about this as there are too many products to discuss here.
Combination products like Cobalt (pyrethroid plus OP) are also becoming very popular choices in wheat and other crops. They bring the good and the bad of both chemistries. Mainly they are being used to increase residual control slightly, avoid resistance to either class of chemistry, and to pick up mite control.
Action Plan
So what should you do about insects in wheat this year? The answer is:
- Scout regularly with a sweep net. Do this BEFORE any other types of spray applications are made as insecticides can be easily tankmixed with most other applications.
- Run a return on investment analysis. Since insecticides like the pyrethroids can often be purchased for only $2/acre, even at $4 wheat it doesn’t take many insects to justify treatment. Before you simply accept anyone’s “economic threshold” for an insect you may have in your field, be sure to find out how much they are figuring for the cost of the insecticide, the value of the wheat, and the potential yield loss. What we commonly find is that numbers are overinflated, meaning that it takes far fewer bugs to justify treatment using today’s economics.
