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Corn nematodes are becoming a problemPosted Tuesday, November 16, 2010, at 2:19 PM
Corn nematodes are becoming more of an interest to corn production.
Less rotation, less tillage and less use of soil insecticides are all raising the risk of damage from corn nematodes according to nematologists from the Corn Belt.
According to Tamra Jackson, plant pathologist at the University of Nebraska, plant parasitic nematodes of corn are often overlooked as causes of disease and yield loss.
According to Jackson, recent changes in cropping practices may favor nematodes. Two significant cropping changes are the adoption of insect resistant Bt corn and the shift to pyrethroid insecticides. Growers have cut their use of traditional carbamate and organophosphate insecticides, which had the side benefit of suppressing nematodes.
These changes, combined with more no-till production and more corn on corn, are likely to encourage the buildup of corn nematodes in the soil.
Nematodes injure corn plants by feeding on the roots and by creating wounds that allow bacteria, fungi and other pathogens to infect plant tissue. There are 60 species that can impact corn. A common misconception is that the microscopic roundworms are only a problem in sandy soils. While corn growing in sandy soil is more susceptible to nematode damage, sandy soil is a risk factor for only a few species such as needle, sting, stubby-0root and root know nematode. Plenty of other species infest heavier soils, including lesion, dagger, lance, ring and stunt nematode. Lesion and sting nematodes are the ones people tend to notice which even at low numbers can cause significant damage.
There is little that can be done during the growing season to rescue the crop from nematode damage. If you know you have a nematode problem you can delay planting by a week or two, apply a good starter fertilizer and irrigate to get the plant off to a good and quick start. A plant with a good root system can withstand nematodes better. A few other things that you can try include (1) Identify the problem by soil and root sampling, (2) Rotate to non-host crops, (3) fertilize according to soil test, (4) control weeds, (5) apply control chemicals.
Because corn nematodes are probably increasing in many areas, it is important to monitor populations. Many nematode experts suggest sampling in spring, within four to six weeks of planting. You can collect samples mid-season, when corn nematodes populations are highest. However mid-season sampling might miss some of the most damaging nematodes, such as needle nematode, which can migrate deep into the soil in the middle of summer. Avoid sampling when the soil is very wet or very dry.
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As our local University of Missouri Agronomy Extension Specialist, Crook has been writing a column for the print edition Agriculture page for the past three years and we will now be sharing it on our web version. Crook has a bachelor and masters degree in agronomy from University of Missouri and received his doctorate in Agronomy from Kansas State University. He was in soybean variety development research for 22 years for various seed companies and has been Saline County's agronomy specialist for 10 years.
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