Weighted Nematode Rating
Weighted nematode rating (WNR) is an easy and inexpensive way to rate root knot nematode damage where cotton follows cotton. This method does not require soil samples or a laboratory to extract nematodes because roots are rated in the field. Rating is based on relative intensities of root galling.
Start sampling at harvest time. Before you begin, draw a map dividing any areas in the field that differ in soil texture, cropping history, or crop injury. Further divide the areas where conditions are most uniform into smaller blocks, using a grid pattern.
Sample each block separately; blocks should be no larger than 10 acres (4 ha). Use a root lifter such as a carrot or beet lifter attached to a light tractor to easily lift cotton roots out of the soil. Record ratings on the WNR form .
How to sample: