Impact of Herbicides on Fruit Drop

Josh McGillAll In For Citrus Podcast, Fruit Drop, Herbicides

Growers know the negative impacts of any kind stress on trees infected by HLB. That raised a question: Can injury from herbicides make fruit drop worse? Ramdas Kanissery, an assistant professor of weed science with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), conducted a research project to help answer that question.

This citrus dropped due to glyphosate spray injury. (Image courtesy of Steve Futch, UF/IFAS)
Ramdas Kanissery

Kanissery discusses the research in the May All In For Citrus podcast episode. He says the starting point for growers is to ensure they are making herbicide applications properly and following label instructions. He says preventing off-target drift of herbicides is important to avoid tree injury. The use of adjuvants can help reduce drift and improve herbicide performance. Proper boom height and using the right nozzles also are crucial. In addition, applications should be made at the right volume and pressure.

His study looked primarily at glyphosate and its potential to harm trees, even when applied correctly. Kanissery says the results after two years of trials show that groves treated with glyphosate didn’t show any signs of increased injury or fruit drop. However, he did find avoiding glyphosate applications in early spring just prior to harvest in Valencia may provide a small yield benefit.

Kanissery also studied the effects of pre-emergent applications of diuron and indaziflam herbicides in Hamlin. High, medium and low rates of herbicide were tested. There were no significant differences between the treated plots and the untreated controls.

“The key is avoiding herbicide contact with citrus foliage and fruit,” Kanissery said.

To hear more about this research, tune in to the May All In For Citrus episode. The podcast is a joint project of UF/IFAS and AgNet Media.

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