Selective control of Orobanche ramosa in potato with rimsulfuron and sub-lethal doses of glyphosate

Previous studies indicated that foliar applications of rimsulfuron were effective in controlling Orobanche ramosa but phytotoxic to potato plants, while sub-lethal doses of glyphosate slightly reduced Orobanche infestation but were selective in potato. In this study, a single foliar application of rimsulfuron at 12.5 g ai/ha followed by single and sequential foliar applications [20, 35, 50 days after potato emergence (DAPE)] of sub-lethal doses of glyphosate (100, 200 and 300 g ai/ha) were used. All doses except the single application of rimsulfuron followed by sequential applications of glyphosate at 200 and 300 g ai/ha had no negative effect on potato growth and marketable yield, but had variable effects on Orobanche infestation. All doses significantly reduced Orobanche shoot number 75 and 90 DAPE, while triple application of glyphosate following rimsulfuron was the most effective in reducing Orobanche shoot number after 110 DAPE and dry weight compared to the control. The best results considering both Orobanche control and selectivity in potato was obtained by application of rimsulfuron at 12.5 g ai/ha followed by sequential foliar application (three times) of glyphosate at 100 g ai/ha.