Fall 2011 Field Observations

Reniform nematode causing problems for local growers

by Jim Bethke

The reniform nematode, Rotylenchulus reniformis Linford and Oliveira, causes economic damage (up to 10% losses) to cotton, sweet potato and other vegetable crops in the continental United States, and to pineapple in Hawaii. At present, there are no field populations of reniform nematode in California and regulators would like to keep it that way.

The California Code of Regulations mandates that nursery stock shall be commercially clean with respect to economically important nematode species detrimental to agriculture, and incoming and outgoing shipments need to be free from these nematode pests to fulfill phytosanitary quarantine requirements. Thus California recently halted several shipments of potted plants from Hawaii due to infestations of reniform nematode, causing great concern for both California and Hawaii agricultural inspectors. An investigation identified an isolated source of infested cinder, and the issue has been resolved for now. Unfortunately, the nematode was also detected in potted plants in San Diego and Riverside counties during inspections in 2011.

There are no highly effective nematicides left in California, which means that an effective eradication treatment eludes the ornamental plant industry. Therefore, if plant parasitic nematodes are present, shipments will be held for treatment and re-inspection, and potentially may be destroyed. Further, without a proper identification of immature stages of nematodes, regulators have no choice but to err on the side of caution to protect vulnerable agriculture. Our trading partners do not want the problem sent to them either.

Graphic by Charles Overstreet. Source: Nemaplex Virtual Encyclopedia on Soil and Plant Nematodes, http://plpnemweb.ucdavis.edu/nemaplex/Taxadata/G116S2.HTM