March 10, 1998
Planting soybean varieties resistant to the destructive soybean cyst nematode is an effective strategy for managing the nematode. However, it's not a recommended strategy in fields with high nematode egg density, according to a University of Minnesota scientist.
Senyu Chen, nematologist at the U of M Southern Experiment Station at Waseca, says high nematode egg density means more than 5,000 eggs per 100 cubic centimeters of soil. "Above this level, significant yield loss may occur, even with a resistant variety," he says. "Planting a non-host or poor host crop is a better option, and should reduce the nematode population."
In 1997, Chen evaluated 20 soybean varieties at Waseca and 19 at Lamberton. He studied egg density counts from soil samples collected at planting and at harvest. At planting, there were 7,460 eggs per 100 cubic centimeters of soil at Waseca, and 12,667 at Lamberton.
"At Waseca, resistant varieties reduced the average egg density 57 percent," he says. "There was no significant change for susceptible varieties. At Lamberton, resistant varieties reduced egg density by 48 percent, and susceptible varieties increased the egg count 88 percent."
Chen says resistant varieties generally produced higher yields than susceptible varieties in fields infested with the nematode. The yield advantage at Waseca was 5.2 bushels per acre; at Lamberton it was 9.8 bushels per acre. At both sites, the higher the nematode egg density at harvest, the lower the soybean yield.
"Egg density at harvest indicates the level of resistance or susceptibility of a variety," says Chen. "Thus, it is evident that soybean yield increased with increasing level of nematode resistance in fields infested with the nematode. However, it is important to remember that the yield potential of a resistant variety depends on a number of factors. Some of these are agronomic characteristics, resistance to other diseases and pests, soil factors, weather conditions, and cultural practices."
Chen says the soybean cyst nematode is one of the most significant yield-limiting factors of soybeans in southern Minnesota, and appears to be spreading in that region.
Source: Senyu Chen, (507) 835-3620
Editor: Joseph Kurtz, EDS, (612) 625-3168,pkurtz@extension.umn.edu
News Page