Florida fruit and vegetable farmers who use mulch to discourage nutsedge may find a bigger payoff if they bet on black — black plastic mulch, that is.

University of Florida researchers found the popular material performed better than five other mulch varieties at suppressing nutsedge in tomatoes. The findings were presented at the 5th International Weed Science Congress, held in Vancouver, British Columbia, Canada.

Nutsedges are among the world’s most problematic agricultural weeds, and impact virtually every crop grown in Florida.

The study was one facet of a larger project that aims to develop a nutsedge suppression system using hay infested with the fungal biocontrol agent Dactylaria higginsii, which kills nutsedges, said senior author Yasser Shabana, program manager of weed biocontrol at UF’s plant pathology department, part of the Institute of Food and Agricultural Sciences.

Shabana and colleagues at UF, the U.S. Department of Agriculture and the University of Puerto Rico evaluated the mulches, using raised beds planted with tomato seedlings and purple and yellow nutsedge tubers.

Black plastic mulch performed best, followed by green sorghum, green millet and cogongrass hay mulches, said Shabana, who presented the study. Cogongrass hay best suppressed tuber formation in both purple and yellow nutsedges. Altogether, the researchers tested two plastic mulches, four green mulches and 10 organic hays for their ability to suppress nutsedge.

The research was partly funded by the USDA’s Tropical and Subtropical Agricultural Research program.

Next year, researchers will evaluate combinations of plastic mulch and hay, some of which will be treated with the fungus, Shabana said. They aim to find the combination that best discourages nutsedge, providing mechanical barriers plus a dose of the fungus for any nutsedge plants that emerge.

The strain of Dactylaria higginsii used in the research was discovered by a UF graduate student, and has been awarded two U.S. patents.