Nematode Parasites Found In Mint

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Modified from Russell Ingham and Kathy Merrifield. 1996. A Guide to Nematode Biology and Management in Mint. Integrated Plant Protection Center, Oregon State University, Corvallis. Pub. No. 996. 38 p.

Nematodes that can be recovered from mint fields may possess a slender (generally hollow) needle-like feeding structure called a stylet or may have a large opening behind the mouth. Those without stylets feed on bacteria or other small organisms which can be swallowed hole. Some have primitive teeth and are predators of other nematodes. Species of nematodes with stylets may be plant parasites or feed on fungi, algae or other nematodes by inserting the stylet into the food source and sucking out cell contents. Many have a muscular structure in the esophagus which pumps the cell contents through the stylet and into the gut of the nematode. In addition to removing cell contents, the insertion of the stylet into plant cells causes structural damage.

Horner and Jensen (1954) were the first to examine plant-parasitic nematodes from mint plantings in Oregon. They recovered northern root-knot nematodes from spearmint and determined that this nematode would parasitize peppermint as well. Pin nematodes were present in most fields examined and earlier had been associated with fungi causing rhizome and root rot (Horner, 1952). Mint nematodes were associated with many areas of stunted and dying peppermint that exhibited a root die-back condition. Underground mint shoots were found infected with foliar nematodes, with as many as 400 nematodes in a single root tip. However, these nematodes could not be recovered from shoot tips after shoots had emerged from the ground. In a 1986 survey evaluating 238 samples from mint fields in Oregon, Ingham (unpubl.) found lesion, pin, stubby-root, mint, ring and root-knot nematodes in 91%, 86%, 9%, 2%, 2% and 1% of the samples, respectively. Lesion and pin nematodes were also the most abundant with 30% and 43% of the samples having more than 2000/quart soil of lesion or pin nematodes.