Citrus growers have multiple options in their weed management toolbox to tackle such problems as parthenium, ragweed, sweet clover and amaranth. Ramdas Kanissery, weed scientist and assistant professor at the University of Florida Institute of Food and Agricultural Sciences Southwest Florida Research and Education Center, believes the right tool or combination of tools can improve yields and help protect trees.
“Weed management in citrus is one of the key ingredients for a successful and profitable production … Weeds can compete with citrus trees for nutrients, moisture and resources and can have an impact on the yield,” Kanissery said. “We are seeing some observations that maintaining weed-free tree rows can really increase the yield, at least 25 percent.”
Kanissery’s weed management strategies are divided into four categories: prevention and cultural, mechanical, chemical and thermal.
Prevention and cultural options include implementing cover crops and mulch in the groves. Cover crops help reduce weeds and improve the quality of the soil.
Mechanical options include disking and mowing between the rows or trees.
Chemical alternatives involve herbicide use. Some are used post-emergence, after the weeds have emerged out of the ground. Others are used pre-emergence, before the weeds can emerge.
Kanissery stresses the importance of preventing herbicide injury to young trees. Growers need to maintain proper boom height, deliver the herbicide to the target, avoid tree foliage and fruit contact and apply special care for new plantings.
Growers can protect newer plantings by using a lower range of labeled rates and install protective wraps around the trunks.
Thermal or steaming options are non-chemical weed treatments that are sustainable.
“My favorite is to mix more than one tool to suit the particular grove’s needs. The chemical tool is easily accessible and has long-term impact, but if it’s not possible, there’s always options for mechanical control and cultural control,” Kanissery said.
He added that to prevent a weed outbreak in citrus groves, growers need to stop the weeds from getting to seed. For example, goatweed has tiny seeds that are released from the seed pods. Each plant can potentially add hundreds of thousands of seeds to the soil. The same can be said for amaranth/pigweed, parthenium and black nightshade.
“There are a bunch of weeds, depending on where you are — whether it’s in southwest Florida, east Florida, north or central — but a couple of weeds that I keep hearing from growers are Spanish needle, parthenium, ragweed and amaranth. They are heavy seed setters and keep coming and coming all the time,” Kanissery said. “Growers are having challenging periods to control them.”