Source: Jamal Faghihi, Christian Krupke and Virginia Ferris, Purdue University
We always suspected that wheat was a good host for the needle nematode and warned last year to be on the lookout for this nematode on wheat. However, we have never isolated needle nematode from wheat roots before. Two weeks ago a sample from Jackson County was sent by Rick Scranton, Pioneer Hi-Bred, and from this sample we were able to isolate several juveniles of needle nematodes. He is reporting patches of stunted and abnormal looking wheat. He also indicated that the grower previously had similar issues on corn. The root symptoms are similar to those on corn, but because of delicate nature of wheat roots, the symptoms are not very obvious. The tips of the roots are truncated and resemble herbicide injury. Like corn, the above ground symptoms do not follow a regular pattern and are usually in patches.
We might speculate that needle nematodes start their invasion of wheat roots in the fall. Early in the following spring, when soil temperature rises to above 50ºF, needle nematodes can further invade the established wheat roots. The tiny nematodes aggregate around the roots and with the aid of hollow needle-type mouth parts suck the juice out of the wheat roots. Needle nematode activity usually starts when soil temperatures reach 50ºF and usually ceases when soil temperatures rise above 85ºF. If you have noticed patches of stunted wheat in sandy soil and previously had similar issues on corn, needle nematode might be the problem. In this case, you may wish to send the entire root system with adjacent soil to the Nematology Laboratory (address below) at Purdue University for analysis, to rule out the nematodes. Samples must be kept cool and prevented from drying. This is the perfect time to sample for needle nematodes.
The sampling procedures for most nematodes are similar. However, samples for the needle nematode must be taken before soil temperatures become too hot, in corn this is usually within 6 weeks after planting. Soil samples must be taken from a depth of 4-6 inches, as close as possible to the infected plants. It is essential to enclose the entire root system with soil surrounding the infected plants. A more detailed sampling procedure can be found here.
If you have any questions about corn nematodes or any other plant parasitic nematodes, you can contact Jamal Faghihi at 765-494-5901 or send an e-mail to firstname.lastname@example.org. Soil samples for nematode analysis can be sent to: Nematology laboratory, Purdue University, Department of Entomology, Smith Hall, 901 W. State Street, West Lafayette, IN 47907-2089. The cost for nematode analysis for each sample remains at $10 per sample.