The trees are likely to be more susceptible to temperature and water stress. The symptoms described below are indicative of a nematode problem, but are not diagnostic as they could result from other causes as well. Lesion nematode infested trees may appear stunted with very few feeder roots. The roots may have reddish brown lesions that eventually turn dark. The roots have distinctive swellings, called galls.
Dagger nematode causes gall formation on root tips.
If the symptoms described above are present and no cause is evident, the orchard should be sampled to determine if lesion, root knot, dagger, or other plant parasitic nematodes are present. If nematode species have not previously been identified, take soil samples and send then to a diagnostic laboratory for identification. Divide the field into sampling blocks of not more than five acres each that are representative of cropping history, crop injury, or soil texture. Within each block, take several subsamples randomly from the frequently wetted zones at the edge of the tree canopy. Contact your farm advisor for more details about sampling, to help you find a laboratory for extracting and identifying nematodes, and for help in interpreting sample results.