The dagger nematode, X. index, feeds on root tips causing them to swell in a manner similar to the nodosities caused by phylloxera. Virus transmission by dagger nematode produces symptoms on leaves such as yellowing of veins, mosaic, and malformation with symptom expression less apparent among white varieties and in warmer regions. Infestation by root lesion nematode restricts top growth of young vines. If young vines are planted in soil infested with lesion nematode, root systems may be severely restricted and sometimes exhibit brown lesions. Soil adheres to roots infested with citrus nematode giving them a dirty appearance.
Ring nematodes cause general aboveground lack of vigor and reduced vine growth and yields.
To make management decisions, it is important to know the nematode species present and to estimate their population. If a previous orchard or vineyard had problems caused by nematodes that are also listed as pests of grape, population levels may be high enough to cause damage to the young vines. If nematode species have not previously been identified, take soil samples and send them to a diagnostic laboratory for identification. Take soil samples from the berm area 12 to 18 inches from the vine trunk to a depth of about 30 inches. Include some feeder roots in the sample.