Once nematodes are discovered in a sugarbeet field, the most common and obvious solution is to plant a nematode-tolerant sugarbeet variety. While tolerant varieties are a viable solution, university field trials now show that sugarbeet yields can be even higher when soil fumigation is also part of the solution.
Dr. Saad Hafez, University of Idaho extension nematologist, conducted such a field trial in 2013 at the Parma Research Center. In that trial, six different proprietary nematode-tolerant varieties were planted into a field with medium/high cyst nematode pressure (averaging 10 viable cysts per 500 cc of soil). A standard, “susceptible” variety was also planted. The same seven varieties were also planted into plots that had been fumigated with Telone soil fumigant. Using a strip-till machine, Telone was broadcast applied at 12 gallons per acre in November 2012. Planting took place in late April 2013. There were four replicates per treatment.
Impressive Results
In October 2013, all plots were harvested and yields were measured.
“The results were a real eye-opener,” Hafez said. “Yields for all six of the nematode-tolerant varieties were higher when soil fumigation was added. Three of the varieties had yield increases of 25 percent or more. Yields for the susceptible, ‘non-tolerant’ variety were more than doubled where Telone was used.”
Hafez estimated that 60 percent of the sugarbeet ground in Idaho has some level of cyst nematode. Soil sampling remains the best method of determining the presence and the population level of cyst nematode.
“Once presence is established in a field, most growers believe using tolerant varieties will be enough,” Hafez said. “Maybe it will be, and maybe it won’t.
“One thing, for sure, is that a cyst nematode problem cannot be corrected after planting. Eighty percent of the damage caused by cyst nematodes occurs within eight weeks of planting. That’s when you will see stunted plants, a poor stand and yellowing plants. At that point, it is too late to catch up, and this is why treatment before planting or at planting is a must.”
Nematode Pressure Increasing
Cyst nematode populations at the Parma Research Center trial site were fairly high.
“Most commercial fields don’t have the nematode pressure we have at the station,” Hafez said. “But there are pockets in eastern Idaho that have high pressure. We’ve analyzed samples from Magic Valley with 40 to 50 cysts per 500 cc of soil. Possibly, shorter crop rotations are partly to blame.
“Our research shows that fallowing alone will drop the population of viable cyst eggs by 40 percent every year. The longer the rotation away from a host crop, the fewer viable eggs will be in the cyst.”
Prepare in the Fall
While treatment for cyst nematodes must take place before, rather than after, planting, Hafez encourages certain pest control decisions be made in the fall.
“We recommend that growers prepare nematode management plans for the next year’s crop in the previous fall,” he said. “Here’s an actual example of why that is important: a grower brought us a soil sample in February from a field in which he wanted to plant potatoes. We found 2,000 root knot nematodes per 500 cc of soil, an incredibly high number—too high to plant potatoes.
“But the field had already been bedded up specifically for potatoes and knocking down the beds wasn’t an option. At that point, the grower’s options were limited. With the same nematode population knowledge in the fall, that grower has more options.”