Dr. Robert Kemerait, Plant Pathologist, Cooperative Extension Service, University of Georgia, P.O. Box 1209, Tifton, GA 31794
Phone (229) 386-7495
FAX (229) 386-7415
email: kemerait@arches.uga.edu
Major Nematode Species: Three species continue to be major threats to Georgia's cotton production -- southern root-knot, Columbia lance, and reniform nematodes. The root-knot nematode is the most widespread and occurs in all cotton producing areas in the state. The Columbia lance nematodes is the most damaging type to cotton, and occurs most frequently in east and middle Georgia. The reniform nematode is found mostly in soils with higher clay content in middle Georgia.
Other Nematode Species: Lesion and sting nematodes are of growing concern to Georgia’s cotton producers. In 1994, lesion nematodes were identified in one or more soil samples in 35 cotton producing counties. Sting nematodes were first officially reported in 1995 in two counties, although their presence had been known for several years. In 1997, 25 counties identified sting nematodes at low level infestations.
Cotton Nematode Population Density Changes Reported in 1998: 15 counties reported density changes during the season for one or more species, as follows: Berrien -- lance nematode from low to medium; Bleckley -- reniform nematode from medium to high; Burke -- root-knot nematode from medium to high; Calhoun -- root-knot nematode from low to high; Colquitt -- reniform nematode from low to high; Decatur -- root-knot nematode from medium to high; Dooly -- reniform and lance nematodes each from medium to high; Dougherty -- reniform nematode from none identified to low; Houston -- root-knot nematode from low to medium; Jenkins -- root-knot nematode from low to medium; Marion -- root-knot nematode from none identified to low; Pulaski -- root-knot nematode from medium to high ... reniform nematode from low to high ... lance nematode from medium to high; Randolph -- root-knot nematode from low to medium; Treutlen -- root-knot nematode from medium to high; and Worth -- root-knot nematode from low to high.
1998 Yield Loss Estimate Valued at $390/Bale: 8% of the crop was lost to nematode damage ... 137,423 bales ... valued at $53,594,970.
Eight-year Average Yield Loss Estimate - 1991 to 1998: Annual average of 5.75% of the crop was lost to nematode damage ... 97,871 bales ... valued at $37,606,220.
1999 Activities to Consider in Latter Part of Growing Season: The recommended time to extract nematode soil samples in the latter part of the growing season.
Growers can reduce nematode populations below damaging levels with the technology and nematode management practices that are readily available. The rewards of controlling cotton nematodes are well worth the cost and effort.
1998 Research Activity: Eight field tests were conducted during the season. Four trials were done to determine the effects of selected nematicides on root-knot nematodes (two in Tift county, one in Montgomery county, and one in Colquitt county). Four tests were conducted to evaluate precision farming technology for control of root-knot nematodes (two in Mitchell county and two in Baker county).
For details of test results, contact Jennifer Gimpert.