Des Moines, Iowa
March 16, 2009
Pioneer experts recommend
sampling soil, rotating crops and sources of SCN resistance
Soybean growers have a better chance of controlling soybean cyst
nematode (SCN) populations by rotating SCN resistance sources
and planting non-host crops, say agronomy experts at
Pioneer Hi-Bred, a DuPont
business. Using only one source of resistance may mean some SCN
races aren't controlled. Combining soil testing to determine egg
numbers and race along with the right Pioneer® brand variety
could go a long way in managing this serious soybean pest.
SCN, the single most damaging pest of soybeans, continues to
spread in northern areas of the Corn Belt. Managing this pest
requires scouting, sampling, and rotating crops and sources of
SCN resistance.
"Soil sampling and rotating sources of SCN resistance act as a
check and balance for growers," says Jim Boersma, Pioneer area
agronomist based in Minnesota. "Growers can monitor SCN
management by sending soil samples to their University nematode
laboratory every few years. Rotating sources of resistance is
vital to ensure one race or population of SCN doesn't become
dominant."
To further understand the impact of SCN and its life cycle,
Pioneer agronomists and field staff conducted multiple on-farm
SCN trials in 2008. The goal was to compare the increase in SCN
egg density for one growing season that occurs when three types
of varieties are planted: nonresistant, PI88788 source resistant
and Peking source resistant. Four varieties were planted in 25
different Minnesota sites: a Pioneer variety with the PI88788
source, a Pioneer variety with the Peking source, a Pioneer
variety with no SCN resistance and a competitor's variety with
the PI88788 source. The Peking and PI88788 are two sources of
SCN resistance used by Pioneer soybean breeders to decrease the
egg count of SCN.
"We found there is significant value using SCN-resistant
varieties," Boersma says. "In non-SCN-resistant varieties
tested, there was an average increase of nearly 10,000 eggs per
100 cubic centimeters of soil." Soil was collected at each site
within each variety plot in both the spring and the fall to
measure the seasonal increase in egg density.
At the 25 locations, one of two Peking varieties was planted -
Pioneer varieties 90M80 and 92Y20. 90M80 was planted in central
Minnesota sites and 92Y20 was planted in southern Minnesota
locations. Both varieties were effective in keeping egg counts
significantly lower than the non-SCN variety. The PI88788
varieties planted were 91M80 or 92Y30. In the study, the Pioneer
PI88788 varieties had a 1 bushel yield advantage on average
compared to Pioneer varieties with the Peking source and the
competitor PI88788 varieties. Many of the Pioneer varieties with
the PI88788 source have brown stem rot protection, which could
explain why that source performed well.
"These results show that yield levels were fairly consistent for
either source of SCN resistance," Boersma says.
Boersma encourages growers to rotate SCN sources and varieties
each year soybeans are planted to keep SCN in check since each
source of resistance controls different races of SCN.
"The Peking source controls races 1, 3 and 5 and PI88788 is
effective against races 3 and 14," he says. "Make sure you know
which source of resistance you are planting."
Pioneer agronomists and extension specialists are confirming
that SCN in some fields is no longer controlled by the most
common sources of SCN resistance, the PI88788 source, almost
certainly due to overuse of this single source of resistance.
For this reason, Pioneer breeders use diverse sources of SCN
resistance. Pioneer soybean breeders also work with breeding
tools such as marker-assisted selection (MAS) and Accelerated
Yield Technology (AYTTM) methods to develop higher-yielding,
genetically diverse and proprietary Pioneer soybean varieties.
"To properly minimize losses from SCN, the bottom line is to use
all management tools," says Boersma. "Growers need to rotate
sources of resistance, use crop rotation and soil sample fields
to monitor SCN pressure."
For more information on SCN symptoms, development and management
considerations, click here.
Pioneer Hi-Bred, a DuPont business, is the world's leading
source of customized solutions for farmers, livestock producers
and grain and oilseed processors. With headquarters in Des
Moines, Iowa, Pioneer provides access to advanced plant genetics
in nearly 70 countries.
DuPont is a science-based products and services company.
Founded in 1802, DuPont puts science to work by creating
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