How to Enhance Pre-emergent Herbicide Performance

Daniel CooperTip of the Week, weeds


By Ramdas Kanissery and Robert Riefer

Pre-emergent herbicides, also known as residual herbicides, are highly effective in the long-term suppression of weeds in citrus tree rows. These herbicides remain in the soil and prevent susceptible weeds from germinating.

In order to achieve the best weed control results, pre-emergent herbicides need to stay within approximately the top 5 inches of soil, where they can effectively suppress the germination of weed seeds. However, Florida’s citrus soils have a high sand content, which causes the herbicide’s active ingredients to leach more rapidly from the topsoil. This leads to a reduction in herbicide performance.


To tackle this problem, a University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) project was conducted to assess the potential of adjuvants called “soil-binding agents” or “soil deposition agents” in enhancing the retention and effectiveness of pre-emergent herbicides in Florida’s sandy soils. One such herbicide tested was flumioxazin (trade name: Chateau). It was combined with a soil-binding agent called polyvinyl polymer (trade name: Hydrovant-fA). The mixture, consisting of 8 ounces per acre of the herbicide and 0.1% v/v of the soil-binding agent, was applied to the citrus tree rows. The mixture’s weed-control effectiveness was compared to using herbicide alone.

The results of the experiment showed that the combination of the pre-emergent herbicide and the deposition agent improved overall weed-control efficacy compared to using the herbicide alone. These findings indicate that incorporating these adjuvants has the potential to enhance the effectiveness of pre-emergent herbicides in controlling weeds in citrus groves. 

  • Pre-emergent herbicides are essential for keeping weeds under control in citrus groves throughout the year.  
  • To effectively prevent weed germination and growth, pre-emergent herbicides must stay in the upper layer of soil.  
  • Mixing soil-binding agents with pre-emergent herbicides improves their effectiveness in sandy soils by helping them stay in the soil for longer periods.

Ramdas Kanissery is an assistant professor, and Robert Riefer is a biological scientist, both at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.

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