By Clint Thompson
The time in between production seasons provides Florida vegetable producers a chance to manage nematodes. While cover crops improve the soil quality and health in preparation for the upcoming growing season, they can also help reduce nematode reproduction; if growers implement cover crops that are poor hosts.
“It’s basically got to be a decision a grower makes based on how well he knows his field. Knowing what nematodes you have in your field is really the first thing you need to figure out,” said Johan Desaeger, Assistant Professor of Entomology and Nematology at the UF Gulf Coast Research and Education Center. “Then you can decide which is the best cover crop or cover crop mix you can use.”
By increasing the soil’s organic matter, cover crops can also improve the soil health by stimulating biological control organisms that are nematodes’ natural enemies, Desaeger said.
But what cover crops are recommended? It depends on what nematodes have been a problem in growers’ fields.
“It depends on the nematode issue that you have. For root-knots, we’ve looked at sunflowers, and sunflowers is a good host for all root-knots that we looked at. That’s not something I would recommend. Another one that is very common is cowpeas, and that depends on the root-knot species that you have. It grows very well and is good for the soil, but it certainly can increase certain species of root-knot nematode,” Desaeger said. “Sorghum-sudan is another good one for root-knot, but it’s not a good one for sting or stubby.”
Sunn hemp is a good cover crop to use. It produces high amounts of biomass and is a poor host to root-knot nematodes and sting nematodes. It also contains alkaloids in its tissue. Its leaf and root residue have nematicidal activity, says Desaeger.
“It’s extra work. You’ve got to buy the seed. You’ve got to prepare your land. If you plant them in April or May, it can be really dry. So having overhead irrigation so you can actually water them can make a big difference,” he added. “I do realize there’s a lot of concerns that some growers may have with it, but I would say when they have the time to plant it, it’s certainly something I would recommend.”