Glyphosate displays disease control activity in glyphosate resistant crops

Summary Glyphosate is a broad spectrum herbicide used world-wide. Recent studies showed that glyphosate has activities against some fungi that cause diseases in crops. Published studies have demonstrated activities of glyphosate against leaf and stripe rust in glyphosate-resistant wheat, and against Asian soybean rust (ASR) in glyphosate-resistant soybeans. Past studies showed that glyphosate provided both preventive and curative activities against Puccinia triticina Erikss., and Puccinia striiformis Westend., which cause leaf and stripe rusts in wheat, respectively (Feng et al. 2005). Rust control was demonstrated at multiple plant growth stages with a glyphosate spray rate of 0.84 kg ha −1 which is the typical use rate for weed control. A field test under realistic stripe rust pressure confirmed the preventive and curative activities of glyphosate. Greenhouse studies showed that glyphosate provides both preventive and curative activities against Asian soybean rust (ASR) caused by Phakopsora pachyrhizi H. Sydow Sydow, in glyphosate-resistant soybeans. Rates of 0.84 to 1.68 kg ha −1 of glyphosate were necessary to provide consistent activity, although the level of activity was equal to or less than that of fungicide standards. Application of glyphosate prior to rust inoculation delayed the onset of ASR for 14 to 21 days. Glyphosate also displayed curative activity when applied within 5–6 days after rust inoculation. Activity was attributed to systemic glyphosate that required plant absorption and translocation; little to no activity was observed with the surfactant system in a commercial glyphosate formulation. Field studies conducted in Argentina, Brazil, South Africa and USA showed good translation of greenhouse data with reduction in field severity of