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Controlling the Harmful Effects of Nematodes

Dr. Terry Kirkpatrick’s responsibilities with the University of Arkansas Division of Agriculture include both research and extension activities, with most of his research directed toward the biology, ecology, and control of nematodes and soil borne pathogens in soybean and cotton production systems.  He supervises the Arkansas Nematode Diagnostic Laboratory and the annual Arkansas Soybean Cultivar Disease Screening Program.  Dr. Kirkpatrick is a member of the University graduate faculty and regularly advises students at the M.S. and Ph.D. level.

“You’ve got to know what nematodes you’ve got, you’ve got to know where it is, and you’ve got to know how bad it is.”

Dr. Terry Kirkpatrick’s main area of research is the successful management of nematodes, microscopic roundworms which can negatively affect soybean crops.  According to Dr. Kirkpatrick, the problem with nematodes is not their eradication, which is practically impossible, but controlling their numbers so that their harmful effects on soybean crops are negligible.

Three types of troublesome nematodes identified by Dr. Kirkpatrick are: 

  • Root-knot nematodes- the most destructive to soybean plants and therefore the most important of the three
  • Soybean cyst nematodes- a historical problem in Arkansas for many years
  •  Reniform nematodes- a relatively new species of roundworm in Arkansas that have surfaced over the past 20 - 30 years and mainly attack cotton plants. The effects of these nematodes on soybean crops are still unknown.

“The question is: How many really bad spots with high population densities in the field do I have? One spot, not a big deal. 40% of the field with a nematode problem? That’s severe. That’s a big deal.”

Dr. Kirkpatrick works closely in conjunction with the Arkansas Nematode Diagnostic Laboratory, which provides services to farmers such as identifying the type of nematodes afflicting their farms and the magnitude of their presence.  One area of concern for Dr. Kirkpatrick is the shrinkage of cotton farms in Arkansas from 800 to 200 acres in the past several years. The soil in these former cotton fields are often infested by reniform nematodes which then affect soybeans planted in the same space.

“Nematodes are parasites. They are a little bit like mistletoe on an oak tree. It’s not to their advantage to kill the crop outright. They need to have a living host to complete their lifecycle.  The day a seed is planted in a field is the last day the farmer has to manage a nematode problem that year.”

According to Dr. Kirkpatrick, root-knot nematodes create “galls” on soybean roots. These lesions make it difficult to efficiently transport nutrients and water up the stalk, resulting in shorter, more yellow than normal plants.  He further notes that nematodes are not mobile, but are spread to new locations via dirty equipment such as muddy tires, or through infected plant material.  Infected fields expand at a rate of three to four feet per year, usually in the direction of the road as that is the path along which the soil is worked. Fields affected by a nematode infestation typically produce smaller yields and also have problems with weed management. Nematodes populations themselves are also difficult to control because delivering pesticides into the soil is a lot more complex than simply applying them to the top of the soil, as is done with herbicides.

“The Soybean Check-off program has been extremely valuable in providing an opportunity for us to work out some of these management programs.”

According to Dr. Kirkpatrick, the Arkansas Soybean Promotion Board’s sponsorship of a statewide survey on past, present, and future soybean fields has been a huge assistance in determining methods for controlling nematode populations. The Arkansas Soybean Promotion Board also funds work on new nematocides (pesticides which specifically target nematodes and their life cycle) and crop rotation programs which implement long term studies to determine how to manage and deploy crops most effectively.

“We’re never going to eradicate it from a field and we don’t need to. What we need is to help it from costing as much.”

With scientists like Dr. Terry Kirkpatrick working at the forefront of nematode research along with the support of the Arkansas Soybean Promotion Board, effective management of these harmful pests is not just a possibility, but an approaching reality.


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