By Matt Reese
While many farmers in Ohio are all too familiar with nematodes causing problems in their crops, corn has not typically been the source of concern. That has changed recently as clever crop product marketers have whipped up a frenzy of concern about soil nematodes wreaking havoc in cornfields and costing farmers big bushels.
Why are the little buggers such a huge concern all of the sudden? Are nematodes a sales gimmick or a legitimate concern for corn?
The reality is a bit of both, according to Terry Niblack, an Ohio State University Extension specialist on the subject.
“Nematodes are native species. They have always been here and then we brought them corn. They tasted it and they thought it was pretty good,” she said. “Every part of the root has it’s own nematode pest. But if you have been farming for a long time, you are probably wondering why we are talking about nematodes now when we haven’t talked about them before. There are two reasons. There are new products to control them and they are increasing.”
One factor in the rise of nematode populations is the increase in no-till.
“No-till strongly benefits one group of nematodes. Tillage squishes them,” Niblack said. “When farmers are unwilling to till up the soil, it allows the nematodes to build up and they are happier in the no-till system.”
Another factor behind the rise of the corn nematodes is more corn and fewer control measures.
“Corn after corn also builds up nematodes that think corn is tasty,” Niblack said. “And most farmers are not using soil applied insecticides any more. If they are, they are chemistries that do not affect nematodes.”
There are some new products, though, that can effectively control the nematode problems in corn whether they are really causing yield loss or not.
“This is a marketing opportunity too,” she said. “We don’t have a lot of data because nobody has done research on this in the last 30 years.”
The reality is that the rising population of nematodes can cause yield loss in corn, but there simply is not much data about the actual populations in fields because nematode monitoring can be a tricky business.
“Nematodes can indeed cause significant yield loss, but it is usually not across the field, just in limited areas,” Niblack said. “They can cause uneven growth in the field. There are not usually dead or dying seedlings, just uneven corn. It is also pretty rare for the damage to be a 1:1 relationship. If there’s damage, it is the result of the holes in the roots caused by nematodes combined with secondary invaders.”
Nematodes are also hard to monitor because there are many kinds that can be prolific in cornfields.
“Typical nematode samples contain 5 to 7 different parasitic genera, this is not the case with SCN in soybeans,” Niblack said. “These nematodes moves down in the soil profile and wait when there is nothing they think is tasty growing there.”
In the future, Niblack hopes to add volumes to the limited corn nematode research that has been done.
“We have just ignored this problem,” she said. “There are no thresholds and no suggested management practices, so we have to use educated guesses and that creates an opportunity for people to try and sell you their new products. We know these products work if there is a demonstrable nematode problem. Just be suspicious when someone tries to sell you something to control nematodes.”