One question that arises as more people look to fungicides and insecticides to help protect their investment as late in the season as possible, particularly in soybeans, is: when is it time to stop spraying? At some point, it's time to let the crop mature, says Willis Smith, Senesac's, Otterbein, Ind.
Smith is a member of the Indiana Certified Corp Advisor's group, and is a guest panelist for Crops Corner and Hoosier Bug Beat columns ion Indiana Prairie Farmer for the next three months, beginning in September. One of the first questions he tackled was when it was time to 'call off the dogs' and forego any more investment in the crop in the field.
"There is a time to spray, and a time to stop," he says. Then he quipped, "If you're trying to figure out how to mount spray nozzles on your combine, you're into revenge spraying. You certainly aren't going to gain anything at that point."
One legitimate question arises with soybeans, though. Since bean leaf beetles can feed on pods, it's important to keep monitoring them into a late stage of development, usually what's called the R 5 stage. Bean leaf beetles can do enough damage on pods that they can allow secondary pathogens to enter the pod, resulting in moldy seed.
Your Extension educator can help provide details on when enough bean leaf beetle pod feeding would be enough to justify a very late-season application. Still, at some point, it's time to stop.
Harvest is the time to sit back and assess the results of what actions you took earlier in the season. Many agronomists note that soybeans sprayed with a fungicide and/or insecticide tend to be brighter colored at harvest, with less damage to beans in the pod. However, the yield payoff can be variable, and has been variable in test plots in the past.
When it comes to corn, spraying fungicide in early August may have thwarted a late-season gray leaf spot outbreak, and may have saved yield. But it may have brought along an unintended consequence, notes Dave Nanda, president of Bird Hybrids, Tiffin, Ohio.
While usually it's a good thing for plants to stay green longer into the fall, meaning they are still packing nutrients into the kernel and making higher yield, this year may be an exception, he notes. Since corn was planted late and maturity is far behind, due to the record-setting cool July, if hybrids stay green either because they were sprayed with fungicides and are healthier, or because they have insect protection traits and remain healthier, the net result could be considerably wetter corn at harvest. That either means postponing harvest date on those fields hoping for field dry-down and gambling you don't get a large wind or hailstorm to do damage to crops in the field, or harvesting at very high moisture contents.
Whether you applied fungicide or not, moisture contents are likely to be higher than usually this year, especially compared to the last five years, Nanda says. This may be the year you want to make sure your dryer is in operating condition long before you're ready to take the combine to the field.