Charles W. Davis Jr, Agronomy County Extension Agent
Cotton farmers in Calhoun County have battled nematodes for years. These microscopic worms often infect plant roots, causing galling, root death, and yield loss. The most common species affecting cotton in Calhoun County are Southern Root Knot and Reniform. Typically, pesticides called nematicides have been placed in the row near the seed at planting. Aldicarb, the most commonly used nematicide, only provides control of nematodes for about six weeks, leaving the plant vulnerable for the rest of the growing season. Aldicarb is a granular treatment, so the zone of effectiveness is small. Other nematicides, such as fumigants (Telone), provide a larger control zone but are much more expensive. In fields with high nematode populations that Aldicarb alone does not control, Telone is an option, but at an additional cost of over $60 per acre. For years, plant breeders have been working on breeding nematode tolerance into cotton varieties with some success. Several nematode tolerant varieties are now on the market.
This growing season, two Calhoun County farmers decided to put one of the nematode tolerant varieties to the test in side-by-side field studies with their most planted non-tolerant variety. Aldicarb was used in each plot since it also has some insect (thrips) control properties. Tolerant and non-tolerant cotton varieties were grown with and without Telone. Clemson Extension was involved in nematode sampling during the growing season and yield evaluations at the end. Based on trial results, nematode tolerant varieties can reduce the need for more expensive nematicides and reduce nematode populations in the soil at the end of the growing season. With crop production costs skyrocketing, using a nematode tolerant variety to minimize the need for expensive nematicides is appealing to cotton farmers. Additional on-farm tests in the coming growing season should help refine the data.
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