June 18, 2009

Nematologist: Weather conditions favorable for needle nematodes

Also known as corn nematode, needle nematode activity usually starts when soil temperatures reach 50 degrees and typically ceases when soil temperatures rise above 85 degrees. Nematode damage is likely to be most severe in sandy soil and where moisture is high. This allows the transparent nematode to move around and find roots to feed on, explained Jamal Faghihi, Purdue Extension nematologist.

The life cycle of the nematode is about one month, he said. The nematodes become active when the soils warm up and feed on corn roots following germination. Unfortunately, late planting does not prevent damage from nematodes.

If these weather conditions persist, Faghihi expects to see increased nematode damage this year. Growers who see patches of yellowed and stunted young corn seedlings in sandy soil may have nematode damage, he said. Nematode feeding causes root growth to be thickened and stubby, with short, stiff root hairs resembling herbicide injury.

Growers who suspect nematode damage should send the entire root system, plus adjacent soil, to a nematology laboratory for analysis. Faghihi notes samples must be kept cool and moist. A sampling procedure is available at https://www.entm.purdue.edu/nematology/samples.html. There is still time to sample for needle nematodes, he said.

The sample should be sent to the Nematology Laboratory, Purdue University, Smith Hall, 901 W. State Street, West Lafayette, IN  47907.  The cost for nematode analysis is $10 per sample.

Corn isn't the only crop affected by needle nematodes. Wheat and other grass crops are also good hosts for the damaging nematode. Unfortunately, once the damage is done there is no rescue treatment, Faghihi said. However, needle nematode does not feed on soybeans.

Other nematodes to be on the look out for include lance nematodes and corn cyst nematodes.  Unlike the needle nematode, the lance nematode is capable of feeding from the outside or inside of roots of corn and soybean roots. These tube-like invisible nematodes feed throughout the growing season and also stunt plant growth.

Corn cyst nematode has not yet been found in Indiana but is present in the Midwest in Tennessee. Still, Faghihi said growers should be vigilant and look at corn root systems for cysts on the roots.

For more information or questions, contact Faghihi at 765-494-5901 or jamal@purdue.edu

Writer:  Julie Douglas, 765-496-1050, douglajk@purdue.edu

Source:  Jamal Faghihi, 765-494-5901, jamal@purdue.edu

Ag Communications: (765) 494-8415;
Steve Leer, sleer@purdue.edu
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