Nematodes

Nematodes are microscopic, unsegmented, roundworms that live in diverse habitats. Plant parasitic nematodes feed on plant roots by piercing and sucking the cell contents with a spearlike mouthpart called a stylet. They usually live in soil and plant roots.

The nematodes listed above have been found in pistachio orchards in California but have not been associated with damage to this crop.

Tree symptoms may suggest but are never sufficient to diagnose a nematode problem. Infested trees exhibit nonspecific symptoms of yellowing, malnutrition, and decline. To adequately diagnose a nematode problem, soil and root samples must be examined by a diagnostic laboratory to determine if nematodes are present.

Although nematodes have not previously been found to cause problems on pistachios in California, if the cause for a problem cannot be found, soil samples could be taken to determine if nematodes are present. Contact your farm advisor for more details about sampling and to help you find a laboratory for extracting and identifying nematodes.

Damage thresholds for nematodes on pistachio have not been developed. If high numbers of plant parasitic nematodes are present and no other cause for symptoms can be determined, contact your local farm advisor for help interpreting sample results and advice.

No management practices are recommended because nematodes are not currently recognized as causing problems on pistachios in California.

In very sandy soils, close attention to irrigation and nutrient management can overcome unthrifty growth conditions in which root knot nematodes may play a role.

Pistacia vera, the commercial nut bearing species, is known to be susceptible to root knot nematode when planted from seed or when used as a rootstock in parts of the Middle East for example. The rootstocks P. integerrima; hybrids of P. atlantica and P. integerrima; P. atlantica and P. terebinthus currently appear to be resistant or poor hosts for root knot and lesion nematodes.