Native nematodes a concern for corn

By Matt Reese

The soil is filled with life, some of which is very beneficial to crops and some that is not. Included in this list are nematodes that have a taste for corn roots, which are a growing concern for many producers as their populations seems to be on the rise. These nematodes are native to Ohio’s soils and crop production practices including no-till and corn after corn have bolstered populations in recent years.

Terry Niblack, an Ohio State University Extension plant pathologist, outlined some of the different types of nematodes that can affect corn in a recent presentation.

 

Needle nematodes

Needle nematodes can kill seedlings. These nematodes and some of the other worst types of corn nematodes usually occur in sandy soils, but Niblack cautions that this does not mean that there can’t be extensive damage in other soil types. So far, Niblack has done much more extensive sampling in Illinois fields (where she worked previously) and has only done limited sampling in Ohio. Niblack found relatively few fields in Ohio with needle nematodes, but there were a couple of fields with high populations capable of causing significant damage.

 

Tylenchids

Tylenchids are one of the most common types of nematodes.

“They have little bitty heads and pointed tails,” she said. “There are a couple of species out of these that we know are pathogenic to corn and the others we just don’t know about.”

 

Spiral nematodes

Spiral nematode. Photo provided by Terry Niblack.

This type of nematodes feeds on epidermal cells and cause damage that allow the secondary invaders to enter the roots and cause problems. In her Illinois research, the glaciated part of the state had a lot of these nematodes while the hilly, un-glaciated part did not. She cautions that even very high levels of these types of nematodes can do very limited damage and are likely not worth treating with expensive products.

 

Lesion nematodes

These nematodes cause damage in corn in some areas and do not cause damage in others. These are endoparasites that into roots and feed on cells.

“They create a lot of holes and kill the cells they feed on,” she said. “They are bad guys.” Many fields are at high risks for damage from this kind of nematode. There are seven different species of this nematode and they are a concern.

“In general, we say that about half the fields in Illinois are at some risk from these nematodes,” she said. “We have fewer samples in Ohio, but found same percentage of these in soil samples as Illinois, so the same applies for Ohio. This is also frequently found with other root rots.”

 

Stunt nematodes

Stunt nematodes are a threat to golf greens and fairways, but not a significant problem in corn. These were very common in the Ohio samples at high enough numbers that they are having an impact.

“We don’t know what they are doing but they are doing something,” she said.

 

Others

Lance nematodes twirl around roots and choke them out, but there have not been many found in Ohio samples. The root knot nematode affects both corn and soybeans and could be a problem in southern Ohio.

 

 

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