The fear of needle nematodes

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.       

Many people, especially kids, fear needles because, simply put, injections are painful. Well, if corn plants could express fear, they too would be wary of needles. In this case however, the needles would be corn needle nematodes, Longidorus breniannulatus. Corn needle nematodes are serious pathogens of corn capable of reducing grain yields 50 bu/A to possibly more. The pain experienced by young plants is exhibited as severe stunting very early in the growing season which often can be observed as early as a week or two after emergence. These stunted plants usually remain in that condition throughout the growing season. If these stunted plants are dug out of the soil, the roots, if fed upon by corn needle nematodes, should have a bottle-brush appearance. As the primary root dies, due to nematode feeding, numerous other roots grow behind it. These symptoms are similar to those caused by some herbicides used in field crops and can be confused with those caused by needle nematodes.

Corn needle nematodes are the longest plant-parasitic nematodes (six to eight millimeters) found in Michigan, and they possess very long stylets. Stylets are similar to hypodermic needles that plant-parasitic nematodes use to wound plant cells and acquire the cells’ contents. Due to the length of needle nematode stylets, many host cells are potentially available to these parasites. Regardless, they are the most destructive nematodes on corn in Michigan.

Corn needle nematodes are typically found in sandy soils (less than 70 percent sand) in fields where corn is often grown. They may occur, or appear to occur, in small clumps in fields due to within field variations in soil types. Corn is certainly the preferred host, but other plants in the grass family can serve as hosts. Management is generally achieved by utilizing rotations with non-host crops such as soybeans and sugarbeets. Conventional at-plant soil insecticides/nematicides are not effective against corn needle nematodes. Once the crop is sown, there is very little that can be done to combat these nematodes.

To properly diagnose a corn needle nematode problem, collect a soil sample(s) and have it analyzed in a nematology lab. The best time of the year to sample for these nematodes is the spring (May and June) or in the fall (September through November). The conditions we’ve experienced this year (cool and wet), should favor needle nematodes. During the summer, corn needle nematodes migrate deep into the soil, two to three feet below the soil surface, to survive periods of adverse conditions. Therefore, fields should be scouted this spring for these important pathogens. If severely stunted corn plants are observed, collect roots and the soil surrounding these roots and send them to Diagnostic Services at MSU for nematode analyses. Information on sampling for nematodes can be found in MSU Extension Bulletin E-2199, “Detecting and Avoiding Nematode Problems.”

Ideally, samples are collected in the fall or before planting in the spring in an attempt to avoid corn needle nematode problems. If these nematodes are detected at damaging levels, corn should not be grown. Adults with young children understand their children often take action to avoid needles. It is advised corn producers do the same. For more information on nematodes on corn in Michigan, please consult our website, http://www.pestid.msu.edu and the factsheet entitled “Corn Nematodes.”  

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