Summary of nematode survey activity in California.

Dr. Peter B. Goodell, Kearney Agricultural Center, University of California, 9240 S. Riverbend Avenue, Parlier, CA 93648, Phone (209) 646-6515, FAX (209) 646-6593


Major Nematode Species: California’s San Joaquin Valley is the cotton center of the state. Cotton is particularly affected by root-knot nematodes in the San Joaquin Valley. Six cotton producing counties in the Valley are Kern, Tulare, Kings, Fresno, Madera, and Merced. Southern counties in the state where cotton is grown include Riverside and Imperial. Recent nematode surveys show root-knot infestations were high in Kern county. Medium population densities were found in Tulare, Kings, and Madera counties. Fresno and Merced counties had low population densities of root-knot nematodes. In a typical season, approximately 900,000 acres of cotton are produced in California. Most of the acreage is planted in Acala. About 20 - 30% of the acres are planted to Pima. Acala varieties have a degree of root-knot nematode tolerance and a resistant variety, CPCSD's NemX, is available.

Other Nematode Species: Three other cotton nematode species have been reported in the state: stubby root, lesion, and spiral nematodes. These species are much lesser threats than the root-knot nematode.

1998 Yield Loss Estimate Valued at $390/Bale: 1.2% of the cotton crop was lost to nematode damage ... 16,399 bales ... valued at $6,395,610.

Seven-year Average Yield Loss Estimate from 1992 through 1998: Annual average of 1.34% of the crop was lost to nematode damage ... 35,000 bales ... valued at $13,136,955.

1999 Activities to Consider in Latter Part of Growing Season: University of California specialists say the best time to sample soil for nematodes is from mid-July through mid-August. That is when nematode populations are their highest, they say, allowing for an accurate count. For management decisions relating to spring planting, however, January and February samples will suffice for providing basic information about nematode levels.

1998 Research Activity: Two investigators -- Dr. Philip A. Roberts, Professor and Nematologist, Department of Nematology, University of California, Riverside, CA 92521, phone (909) 787-4442/7291; and Dr. Peter B. Goodell, IPM Advisor, University of California, Kearney Agricultural Center, Parlier, CA 93648, phone (209) 646-2500 -- conducted studies to determine the following:

Rotation Value and Genetic Characterization of Host-plant Resistance in Cotton to Root-knot Nematode (Meloidogyne incognita): Optimization of Nematode Management and Breeding for Resistance (Project Number 96-293CA)

This study is at year three of a four-year rotation plan.

For details of test results, contact Jennifer Gimpert.