Needle nematodes can be destructive to your vegetables
April 22, 2009 - Author: Fred Warner , MSU Diagnostic Services
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Needle nematodes, Longidorus sp., are often very destructive nematodes. They are the longest plant-parasitic nematodes found in Michigan with the adults measuring six to eight millimeters (ca. one-third of an inch) in length. They possess very long stylets (used for feeding) which allows these nematodes to probe and feed upon cells inaccessible to most other ectoparasitic nematodes.
The common needle nematode, L. elongatus, is a parasite of some vegetables including celery and onions. Mint is also a host. Although they are not detected as frequently as other species of plant-parasitic nematodes in vegetable fields, they are widely distributed in Michigan. The most notable primary symptoms of needle nematode feeding are swollen root tips that may become necrotic (brown). Roots may have somewhat of a “bottle-brush” appearance where after primary roots are killed many secondary or lateral roots emanate from behind the killed root tips. Typically, needle nematode-infected plants are stunted, often severely. Symptoms may develop very early in the growing season and infected plants will invariably remain stunted throughout the rest of the year. Yields will be reduced. Mint growers can potentially experience significant yield losses over time due to needle nematodes. Research data from MSU Nematology Program indicate that losses occur the first year of mint production and this yield lag continues until the crop is finally destroyed. For mint producers, in particular, avoiding needle nematodes is critical.
Needle nematodes prefer sandy, cool, moist soils. They are usually not found in sites where soils contain less than 70 percent sand. Needle nematodes are typically only found near the soil surface during the spring and fall when soils are usually cool and moist. They will migrate to depths of 24 to 36 inches during the summer months to survive periods of adverse conditions. However, if soils remain cool and moist during the early portion of the summer, needle nematodes may remain in root zones longer than usual. Prolonged feeding may result in even more serious symptoms.
As with other plant-parasitic nematodes, the only way to diagnose problems and to assess nematode population densities is to collect soil and plant samples and submit them to a nematode lab for analyses. Unfortunately, if needle nematodes are detected during the growing season, there are virtually no control options other than trying to keep plants fertilized and watered as optimally as possible. As with almost all plant-parasitic nematodes, control strategies and tactics should be implemented before plants or seeds go into the ground.
If you suspect you may have a needle nematode problem, samples should be collected as soon as possible. Needle nematode problems often go undetected due to the behavior of these organisms to migrate deep into the soil. Diagnosis and subsequent management of these pathogens is imperative to avoid losses in the future.
For questions or concerns regarding needle or any other plant-parasitic nematodes, feel free to call me at 517-432-1333, Angela Tenney at 517-353-8563 or Dr. George Bird at 517-353-3890. Nematode samples should be submitted to Diagnostic Services on campus. Please visit our website, www.pestid.msu.edu, for sampling information, to download a form or to find other information about other nematodes, plant pathogens, insects and weeds. There is a $25 for a nematode analysis.