How to Improve Herbicide Efficiency

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) weed scientist Ramdas Kanissery offered numerous tips and observations for improving herbicide efficiency at this spring’s Florida Citrus Growers’ Institute. They included:

• Use optimal herbicide rates. That includes high labeled rates on heavy weed infestations and on weeds in a mature growth stage.
• These post-emergent herbicide mixes will not have favorable outcomes: fluazifop-P-butyl (Fusilade) plus 2,4-D (Embed Extra); glyphosate plus carfentrazone (Aim); and glyphosate plus glufosinate (Scout, Rely 280, etc.).
• When mixing glyphosate and 2,4-D (Embed Extra), avoid mixing issues by increasing water application volumes and by only adding glyphosate when the spray tank is full. 
• Use an appropriate surfactant; it helps improve herbicide retention, coverage and efficacy.
• Use suggested adjuvants.
• Apply herbicide when there is ample sunlight. Mid-day applications enhance the effectiveness of glufosinate. Broadleaf weeds tend to be more sensitive to the time-of-day effect than grasses.
• When spraying during the rainy season, give at least six hours of dry period. Generally, rainfall within six hours after application reduces effectiveness.
• Efficacy of post-emergent systemic herbicides glyphosate, 2,4-D (Embed Extra) and sethoxydim (Poast) is reduced when temperatures are above 95 degrees. At that temperature, injury potential to the tree is also high.
• Spray herbicide when there is low wind.
• Bring pre-emergent herbicides into the weed control program. There can be about 130 million viable weed seeds in an acre of soil.
• Tank mixing pre-emergence residual herbicides helps cut down the rates and manages herbicide tolerance issues.

In addition to discussing herbicides, Kanissery reported that cover cropping, an emergent practice in Florida citrus production, may contribute to longer-term weed management in row middles. Read more on cover crop benefits.

Kanissery is an assistant professor at the UF/IFAS Southwest Florida Research and Education Center in Immokalee. See his full Florida Citrus Growers’ Institute presentation here.

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