Controlling Weeds under Difficult Environmental Conditions. How Can I Control Waterhemp with Ultra Blazer without Injuring my Sugarbeet Crop? (6/10/21)
The good news is sugarbeet growers have been granted emergency exemption to use Ultra Blazer in sugarbeet. The bad news is environmental conditions are challenging, sugarbeet stands are inconsistent, and sugarbeet growth stage range from cotyledon to 6-lf stage in commercial fields in 2021. What is the best way to utilize the Ultra Blazer Section 18 emergence exemption to control waterhemp without severely injuring sugarbeet?
Use of Ultra Blazer in sugarbeet may not be for everyone. Environmental conditions before, during, and after herbicide application impacted sugarbeet safety with Betamix and Herbicide 273 in sugarbeet. Ultra Blazer use will be no exception. Timing to sugarbeet stage, waterhemp height and environmental conditions will need to be very carefully managed with Ultra Blazer. Ultra Blazer is a contract herbicide that causes necrosis damage in crop and weeds as compared to essentially no sugarbeet injury from our current standard, glyphosate with RR sugarbeet. Our evaluation from 2016 to 2020 indicates sugarbeet growth reduction injury is greatest when Ultra Blazer is applied to small beets. Thus, Ultra Blazer application will be reserved for application after sugarbeet have reached the 6-lf stage.
Many contact herbicides are labeled for use with various additives. However, additives also increase the chance for crop injury and we observed less sugarbeet injury when Ultra Blazer was applied with a non-ionic surfactant as compared to oils. Even adjuvants in the glyphosate formulation increased sugarbeet injury when glyphosate was mixed with Ultra Blazer as compared to Ultra Blazer alone.
We have less experience with environmental conditions at application including temperature and humidity conditions. Most contact herbicides, including Ultra Blazer, become more active as temperatures increase. Increased activity may provide improved weed control, but can also result in greater crop injury. Ultra Blazer will need to be used with caution as temperatures increase to greater than 80F. The most critical time for crop injury following application of a contact herbicide is the first few hours after treatment. Therefore, injury can be minimized by applying the herbicide in late afternoon as temperature begins to decreased. Omitting the adjuvant or using the lower labeled rate of the recommended adjuvant will reduce injury potential from Ultra Blazer applied at high temperatures.
Is Ultra Blazer worth the crop safety risks in sugarbeet? I believe so. Ultra Blazer controls waterhemp and waterhemp is currently our most important weed control challenge in sugarbeet. Moreover, we currently do not have an effective POST waterhemp control herbicide since depleting our inventories of Betamix. Finally, yield trial results indicate waterhemp robs sugarbeet yield and reduces recoverable sucrose. We did not observe yield loss or reduction in recoverable sucrose following Ultra Blazer application after the 6-lf stage.
Extension Sugarbeet Agronomist
NDSU & U of MN