HPPD inhibitor (HPPDi) herbicides have been a staple for U.S. corn growers for years. Because of their overall effectiveness and outstanding residual control, HPPDi chemistries are applied to an estimated half of U.S. corn acres*. Now, with the approval the isoxaflutole-based Group 27 herbicide Alite™ 27, growers have the opportunity to use this chemistry on soybeans. While soybean growers have this new tool to tackle difficult-to-control weeds, there are a few things they need to keep in mind about HPPDi chemistries, including their potential effect on next year’s crops with the long half-life of HPPDi products.
Residual Control
One characteristic of HPPDi chemistries is that they provide outstanding residual control, meaning that the ingredients remain active in the soil for a period of time after application and can be reactivated with rainfall. While the longevity of the chemistry’s residual control is a benefit of the chemistry, it can also be a challenge if several variables are in play. Under certain conditions, HPPDi-based chemistries may remain active into the next growing season, which can be a concern if you plan to switch to a crop that doesn’t tolerate HPPDi chemistries. It’s called HPPDi carryover, and soybean growers must proceed with caution as most soybeans are very susceptible to even trace amounts of HPPDi chemistry.
Many of the commonly used corn herbicides with HPPDi products have a 9 to 10 month plant back restriction to soybeans. That said, weather, temperature, soil conditions and more can be determining factors of HPPDi carryover. Dry and cool conditions or late-season herbicide applications can exacerbate this problem. For example, if last year’s corn crop was sprayed late in the season and if dry and cool temperatures persisted throughout the fall and winter, growers may need to lookout for HPPDi carryover this year.
HPPDi Carryover Detection
HPPDi carryover is very hard to identify, and some years may be worse than others. In some instances, HPPDi carryover can appear as bleaching (or white) leaves, but there are other herbicides that can also cause leaves to appear this way, so growers really need to consult with their local agronomist to determine what’s impacting their fields.
Impact on Corn and Soybeans
HPPDi carryover generally does not kill the soybean plant but can be a silent “yield robber.” If you rotated to soybeans, be on the lookout and scout diligently. Carryover is not as much a concern with corn. Most HPPDi products are labeled for corn and should not cause issues as long as you stay within the label for a single application or application amount within a single year. That said, some hybrids are more sensitive than others and weather can play a factor. If you detect symptoms in corn, it’s likely your crop will be fine but contact your local agronomist for further assistance.
Stine® GT27™ and LibertyLink® GT27 soybeans include built-in tolerance to HPPDi/Group 27-based herbicides, providing soybean growers with an additional measure of protection against potential HPPDi/Group 27 carryover. If you plan to rotate to soybeans in 2021 and need an option that tolerates this chemistry, LibertyLink GT27 and GT27 soybeans may be your best option.
For any questions or concerns related to HPPDi carryover, please contact your local Stine sales agronomist. And remember, always read and follow label instruction.
*Source: UPI Market data