The fear of needle nematodes
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EmailEditor’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, www.pestid.msu.edu and the factsheet entitled “Corn Nematodes.”
