- Weather conditions should have been favorable for Needle nematode this spring.
- Stunted corn with stubby roots on sandy soil may be symptoms of Needle or Lance nematodes damage.
- Sampling for corn nematodes is best done about 4-6 weeks after corn germination.
Weather-wise, this relatively cool and wet spring should have been favorable for Needle nematodes. However, based on samples that we have received in nematology laboratory, and it has been plenty, we saw only few samples with Needle nematode. We contribute this to the 2012 drought, as needle nematodes are very sensitive to low moisture and high temperature. In 2012 we started a collaborative study with CERES Solutions on a weekly sampling of a cornfield in southern Indiana with high infestation of various corn parasitic nematodes. We are continuing this project in 2013. Results of this study should provide us a better understating of population dynamics of different corn parasitic nematodes.
Needle nematodes, the most yield-limiting nematodes in Indiana’s corn, need a cool, wet spring and sandy soil to increase in population to economically damaging levels. Other nematodes, like Lance and Lesion nematodes, do not require those conditions to be a problem. While Needle nematode is parasitic to corn only, Lance and most Lesion nematodes can parasitize corn and soybean.
Under high nematode pressure from Needle or Lance nematodes, roots do not develop normally. The roots are truncated and resemble root inhibitor (dinitroaniline) herbicide injury. Lesion nematodes, however, will not cause the described root symptoms. But, symptoms for most plant parasitic nematodes are stunted corn, usually in patches and do not follow a uniform pattern in the field.
The time window for sampling for Needle nematode is probably past, unless you are still experiencing cool and wet conditions. But, you can still sample for Lance and Lesion nematodes. When sampling for corn parasitic nematodes, we strongly advise inclusion of roots with the soil sample, as Lance and Lesion nematodes are mostly inside the roots. You need to send the entire root system with adjacent soil to the Nematology Laboratory, address below, at Purdue University for analysis. Samples should be kept as cool and moist as possible, and recommend shipping early in the week.
The procedures for sampling soil are similar for most plant parasitic nematode species. Soil samples must be taken to a depth of 6-8 inches, as close as possible to the plant roots. A more detailed sampling procedure and sample form can be found on the following website: <http://extension.entm.purdue.edu/nematology/services.html>
Processing fees are determined by the number and complexity of procedures required to determine the total number of plant parasitic nematodes in each sample. The processing charge continues to remain at $10/procedure, however, when both roots and soil samples are submitted, we have to follow two completely different extraction procedures to determine the final nematode counts ($20/sample). For soybean, the cost of processing soil samples to extract cysts and count cysts and eggs from the soil is typically one procedure ($10/sample). We have to process corn samples as quickly as possible because root decay might effect nematodes inside the roots thus we give priority to the corn samples this time of the year.
(Source – http://www.farms.com/news/nematode-updates-corn-parasitic-nematodes-64663.aspx)