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Effects of glysophate application rates and frequency on soybean sudden death syndrome
Plant Pathology Presentations and Posters
  • Shrishail S. Navi, Iowa State University
  • L. Jing, Inner Mongolia Agricultural University
  • Xiao-Bing Yang, Iowa State University
Document Type
World Soybean Research Conference
Publication Date
(-29.857876, 31.027581000000055)
Sudden death syndrome (SDS), caused by Fusarium virguliforme, is a major soybean disease in North America. Outbreaks of SDS have been reported by farmers following applications of Roundup weather MAX (potassium salt of glyphosate 48.8%) at rates higher than recommended. The rate of glyphosate applications have been increasing since the introduction of |Roundup Ready (RR) soybeans in 1996. The United States Department of Agriculture (USDA) data shows that the commercial application rate of Roundup was 9.12 fl oz (0.57 lb active ingredient) per acre in 1996 and in 2006 this was increased to 19.68 fl oz (1.23 lb a.i) per acre. One of the reasons for higher application rates and increased glyphosate application frequency by the growers was to manage glyphosate resistant weeds and the availability of cheaper generic glyphosates. Trials were carried out under greenhouse conditions to understand (a) the effect of glyphosate spray frequency and the varietal reaction to glyphosate sprays at 22 fl oz per acre, and (b) the effect of application rates at 16, 22 and 33 fl oz per acre on SDS incidence and severity. In all trials, soybean seeds were planted in a potting mixture to which 1% F. virguliforme inoculum grown on steam sterilized white Milo was added. Appropriate unsprayed and un-inoculated controls were maintained in all trials. Soybean plants were evaluated for stand count, SDS expression and SDS severity 4 weeks after the application of Roundup. Results of our studies showed that incidence and severity of SDS increased when soybean plants received higher rates and more than one spray at the recommended rate of glyphosate. This suggests that over the years, glyphosate effects on the occurrence of SDS in RR soybeans remain unchanged
Citation Information
Shrishail S. Navi, L. Jing and Xiao-Bing Yang. "Effects of glysophate application rates and frequency on soybean sudden death syndrome" Durban, South Africa(2013)
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