Nature’s pest control

     Researchers at the Oregon State University Klamath Basin Research and Extension Center are looking for crops that can act as natural pesticides during decomposition and be used to keep nematodes from destroying potato fields.

   At the request of the local potato advisory board, researchers began a two-year trial to see the effect of rotating cover crops as a natural pesticide or green manure, said OSU Extension Center potato researcher Brian Charlton.  

   “It’s like a sacrificial crop,” he said. “You grow it. You don’t harvest it and you plow it under.”

   Nematodes, microscopic worms that can infest a potato field and destroy a commercial crop, are some of the most numerous organisms on Earth, but pesticides aimed at reducing or eliminating nematode populations get more costly each year, Charlton said.

   The research station on Washburn Way has been evaluating nine different crops to see what effect they have on known nematode populations, specifically stubby root and root knot types. Charlton said he is collecting data about another parasitic nematode, the root lesion.

   Loss of crops

   There are more than 20,000 named species of nematodes, according to the University of Nebraska. The effect of parasitic nematodes can be a total loss of crops, because even though the produce won’t hurt a person, it doesn’t look good.  

   In the case of the root knot nematode, the potato ends up bumpy. “You get a potato that looks like a bad case of acne,” Charlton said.

   Stubby root nematodes can cause a ringlike discoloration in the potato flesh and skin.

   “We have chemicals   that control these. It’s not like we don’t have tools in the toolbox,” Charlton said. “But they’re expensive.”

   Green manure

   Local potato grower Ross Fleming tried green manure once and said he saw some evidence of benefit.

   “We’re doing it more,” he said. “We’re trying to lower our input costs.”

   Of the crops in the green manure experiment, two radish varieties from The Netherlands seem to have the most promise, Charlton said.

   While the trial results from the first year of the experiment showed poorer results in the radishes’ effect on root knot populations, there was no increase in the stubby root population counts.

   Charlton surmises that the radishes have some kind of property   that hinders the nematodes’ reproductive capabilities.

   “They aren’t going to kill everything there, but there is some mortality,” he said.

   Another plant, Sedan grass, was effective in reducing the root knot population, but increased the stubby root nematode populations 50 times over, Charlton said.

   “No matter how good the pesticidal properties are during decomposition, that’s a trade-off you don’t want to make,” he said.  

   Charlton said he was confident that some Basin potato growers would incorporate green manure crops into their rotations should his research show which is the most effective, but added that many farmers would be unwilling take a field out of production for an entire season.

   “It becomes a question of economics,” he said. “I don’t think we’d see 90 percent of growers do this, but you might find 10 to 15 percent of the potato acres where it would fit. Some are already doing it.”