Dr. Steve Koenning, Department of Plant Pathology, North Carolina State University, P.O. Box 7611, Raleigh, NC 27695-7616, Phone (919) 515-3905, FAX (919)515-7716, (Shipping address -- Central Receiving, Ligon Rd., Raleigh, NC 28607)
Major Nematode Species: The most damaging species to cotton in North Carolina are root-knot, Columbia lance, and reniform nematodes. In a six-county survey in 1990, 200 fields were sampled in Scotland, Robeson, Hoke, Harnett, Cumberland, and Sampson counties. Reniform nematodes were found in 16.5% of the 200 fields surveyed; Columbia lance occurred in 41% of the samples; and root-knot were reported in 85.5% of the field samples. Surveys in 1995 reported a marked increase in frequency of root-knot nematodes. In fields where cotton has been grown for several years, growers can expect above threshold densities of root-knot nematodes.
Other Nematode Species: Other cotton nematode species found in densities below threshold levels in the state include: lesion, stunt, spiral, stubby root, ring, and cyst.
1998 Yield Loss Estimate Valued at $390/Bale: 0.75% of the cotton crop was lost to nematode damage ... 7,984 bales ... valued at $3,113,760. (From 1992 through 1996, North Carolina's annual yield losses to nematodes remained at trace levels. With the escalation of cotton production in recent years, nematode population densities ... and crop yield losses to nematode damage are increasing.).
Two-year Average Yield Loss Estimate from 1997 through 1998: Annual average of 0.63% of the crop was lost to nematode damage ... 6,203 bales ... valued at $2,418,975.
1999 Activities to Consider in Latter Part of Growing Season: The best time to take nematode soil samples is in the latter part of the growing season. As damaging populations of these pests continue to proliferate, growers are advised to treat for nematodes if they reach economic thresholds. Effective control practices include cultural and chemical controls.
1998 Research Activity: The objectives of the research were to evaluate the effects of certain nematicides on cotton growth and yield in fields infested with root-knot and Columbia lance nematodes using current management practices and cotton varieties.
For details of test results, contact Jennifer Gimpert.