Steam Technique Can Spell Doom for Citrus Weeds

Daniel CooperIndustry News Release, Research, weeds

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Like many farmers nationwide, citrus growers are looking for any edge in their fight against weeds, and they’d rather use fewer chemicals to control the plants, says a University of Florida scientist. That’s because chemicals can get into groundwater, surface water and plants themselves.

Weed scientist Ramdas Kanissery and his colleagues at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Southwest Florida Research and Education Center have developed a steaming technique that utilizes a steamer that’s a on a trailer and pulled by a tractor. The steamer includes tanks that convert water into steam, which is channeled into a structure that applies steam onto the weeds. It can reduce the chemical footprint on farms, while still killing weeds around farmers’ crops.

Weeds, many of which are invasive species, can impede citrus tree growth by intercepting soil-applied chemicals, reducing grove temperatures during freezes and by interfering with harvests, UF/IFAS research has shown.

Kanissery led a study that examined the relationship between how much steam scientists applied to the weeds and its effectiveness in controlling them. Specifically, researchers wanted to see if steam could manage weeds under citrus trees in groves. Farmers want some vegetation between tree rows to help prevent soil erosion, but they don’t want weeds in the tree rows.

In the experiment, when scientists ran the tractor slowly and applied the weeds with a high-flow rate of steam, some citrus weeds, like goatweed and sedges, burned and did not grow back significantly. Other weeds, such as pusley, did grow back, Kanissery said.  

Growers might have to repeat the steam applications, but whether they do and how frequently depends on the type of weeds involved, he said.

“We found from our studies that most weeds did not grow back for more than a month after we applied steam,” Kanissery said. But if growers must repeat steam applications, steam can serve as a potential alternative to chemicals in a citrus weed-management strategy. 

Growers have been using steam to disinfect soil for more than 40 years. That’s because applying steam to soil offers numerous benefits: Hot temperature from steam can kill weeds, bacteria, fungi and viruses in the soil, Kanissery said.   

For this study, UF/IFAS researchers calculated approximate costs for controlling weeds with steam. When steam was used as a tool for weed control in citrus, it cost $17 per acre of grove.

Additionally, growers can use steam under many conditions, including wind and rain, without any concern about drift, runoff or loss of efficacy, said Kanissery, a UF/IFAS assistant professor of horticultural sciences.

In their next research phase, scientists will evaluate using steam to penetrate the soil and kill underground plant parts of weeds, Kanissery said.

“Steam offers immense capability for weed control,” he said. “However, we must investigate its practical use for longer-duration weed suppression. Many of the widespread weeds in citrus and vegetable production have been introduced from prairies and forest environments. So, it is not unusual for these weeds to get exposed to disturbances such as fire.”

The UF/IFAS study is published in the journal Applied Engineering in Agriculture.

Source: University of Florida Institute of Food and Agricultural Sciences

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