While the health benefits of organically produced foods remain controversial, the growth in consumer demand is clear and consistent. Organic production relies on the use of non-synthetic inputs and attempts to model ecological processes in food production. Producer demand has resulted in strict certification standards that must be followed if a food product is labeled “organic.” Crop production using alternative management practices increases the challenges and sometimes the risks. The payoff comes from price premiums that are available for many organically produced food products.

Georgia producers choosing to adopt organic production benefit from a long growing season and generally adequate rainfall. However, the same high temperatures and humid conditions that promote plant growth are also ideal for many pests. Conventional agricultural production often addresses pest management with synthetic pesticides. Those tools are unavailable to organic producers.

Starting in 2017, University of Georgia Cooperative Extension nematologist and assistant professor Abolfazl Hajihassani has led surveys of more than 400 vegetable fields in 29 Georgia counties looking for plant-parasitic nematodes. Ten different genera have been identified. Hajihassani’s group found that root-knot nematode is the most prevalent. He has consequently focused his research on this particular pest.

A grant from the United States Department of Agriculture is supporting the research of Hajihassani and collaborators to discover and integrate biological products and cover crops to control nematodes and weeds in organic vegetable production.

“In certified organic production or on farms transitioning to organic, growers are not allowed to use chemicals. Producers have to use non-chemical procedures, which means that their management approach is very limited,” said Hajihassani, project director for the grant. “In this project, we are trying to integrate a couple of techniques that we know have some efficacy as a single technique against nematodes and weeds to see if combining these strategies will result in the best management of nematodes and weeds and a higher crop yield than the growers’ standard practices.”

The three-year, $500,000 grant is part of the National Institute of Food and Agriculture’s (NIFA) Organic Transitions Program (ORG), which is designed to improve the competitiveness of organic livestock and crop producers, as well as those who are adopting organic practices.

Root-knot nematodes can enter a plant’s roots and move through its cells, where they grow, produce eggs and cause the roots to swell. This reduces the plant’s growth and yield potential in a relatively short timeframe and can lead to severe yield losses for organic farmers. South Georgia’s sandy soils allow root-knot nematodes to reproduce frequently because they can move easily through the soil’s loose texture and infect almost all vegetable crops.

As part of the study, the UGA research team will cooperate with Raffi Aroian, a professor of molecular medicine at the University of Massachusetts Medical School, to identify native strains of Bacillus thuringiensis (Bt) crystal proteins, which have nematicidal tendencies.

“The lab we are working with at the University of Massachusetts Medical School has been working on Bt strains for years, but they have never used these strains against plant-parasitic nematodes. They are going to give us some strains that have had efficacy against nonparasitic nematodes and we will screen those strains in the lab and greenhouse to find out the most effective for root-knot nematode control,” Hajihassani said.

In addition to the Bt strains, the team will research the use of entomopathogenic nematodes (EPNs) — nematodes that can kill other nematodes — and their bacterial metabolites to try to control root-knot nematodes. “There are two known species of entomopathogenic nematodes that produce bacterial metabolites and we are trying to find out which one of those species or their metabolites have nematicidal efficacy against the root-knot nematode,” Hajihassani said.

Because weed control is another concern for organic production and farmers cannot use chemical herbicides, the team will test several cultivars of summer and winter cover crops in the field for the greatest nematode- and weed-suppressive qualities.

“We know which species and cultivars of winter and summer crops have suppressive effects against different common species of root-knot nematodes, in particular the southern and peanut root-knot nematodes. In field conditions, we need to find out the optimum timing for cover crop termination in our environments to get maximum suppression of weeds and nematodes,” he said. “Understanding the role of all these factors will help us integrate the best practices of cover cropping with the most effective bacterial or microbial combinations and commercial biological products for the control of nematodes and weeds in organic vegetable production systems.”

Roger Gates is the agricultural and natural resources agent for University of Georgia Extension, Whitfield County. Contact him at roger.gates@uga.edu.

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