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Brown stem rot, SDS and aphids draw field day attention Tuesday, July 24, 2007
Agri News staff writer
WASECA, Minn. -- Brown stem rot and Sudden Death Syndrome took center stage at last week's Southern Research and Outreach Center's Disease and Insect field day last week in Waseca.
Dean Malvick from the University of Minnesota Extension Service discussed the symptoms of Sudden Death Syndrome vs. the symptoms of brown stem rot.
• There aren't any root symptoms with SDS and no pith browning. There are foliar symptoms, and the leafs will drop off the plants.
• Brown stem rot lacks root symptoms, but there is pith browning and possible foliar symptoms. Leaves will curl up but remain on the plant.
"Many people were sending in samples to be tested and thought what they had could have been Sudden Death Syndrome when in fact they had brown stem rot," said Malvick. "That is why we are putting such a strong emphasis on diagnosing this disease (SDS)."
Brown stem rot needs rotation with non-hosts, utilization of resistant varieties, burial of residues, and the use of biocontrol to be handled, said Malvick. On the other hand, SDS needs improvement of drainage, the use of different maturity groups, management of soybean cyst nematode populations, and utilization of resistant varieties to be managed.
"We are seeing it spread much more than we have in the past," said Malvick. "It is spread by soil moving. Most is still in southern Minnesota."
Malvick hopes farmers continue to monitor their fields and continue sending in samples to diagnose both diseases to successfully manage them.
Aphids were another popular topic at the field day in Waseca. Jim Orf talked about three types of aphid-resistant soybeans. The resistance requires a resistant soybean genotype and a susceptible soybean aphid biotype.
• Complete resistance means almost all the aphids die. It's also easy to develop resistant varieties. While generally effective on few aphid biotypes, resistance may only last for a short time.
• Partial resistance means some aphids die or are unable to reproduce. With partial resistance, it's generally effective on most aphid biotypes and it should last for a long time.
• Tolerance means only a few aphids die. Soybean variety suffers less yield loss and should last indefinitely.
Orf said some partial resistance found in soybean germplasm, but the breeding is only beginning.
"Currently, there is the release of biocontrol agents such as the Asian beattle, and there are several chemicals available for control of aphids," said Orf. "But, those chemicals may also kill some of the biological control of insects."
Vernon Cardwell, a professor in the agronomy department at the University of Minnesota, had his field problems and diagnosis class in attendance at the field day. He said the purpose of field days are two-fold.
"It allows farmers and coops to obtain new technical information and not just find out how to identify the problem, but also ways you can avoid it," said Cardwell.
Cardwell also said farmers have the opportunity to meet who is doing the research.
"If farmers have a problem, they know who their first point of contact is," said Cardwell. "It is a great place to do professional networking." |
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