| Abstract Detail
Plant Protection Pasche, Julie S. [1], Gudmestad, Neil C. [2]. Sensitivity of A. solani isolates to Frac Group 7, 9 and 11 Fungicides. EARLY blight, caused by Alternaria solani, is an important foliar disease of potato requiring routine foliar fungicide applications for effective management. Mancozeb and chlorothalonil alone generally are inadequate to manage early blight full season in the Midwestern US. QoI fungicides (Frac group 11) represented a premium group of fungicides generally providing superior control of this disease. The first QoI was registered for use on potato in the US in 1999 (azoxystrobin), by 2000, reduced-efficacy of azoxystrobin on early blight was observed, due to the F129L mutation, resulting in reduced-sensitivity to azoxystrobin. Subsequent registrations of QoI fungicides occurred in 2001 (trifloxystrobin), 2002 (pyraclostrobin), 2003 (famoxadone) and 2004 (fenamidone). Decreased sensitivity in mutant isolates of A. solani possessing the F129L mutation, compared to the wild type, varied from 10-12X for azoxystrobin and pyraclostrobin to 2-3X for trifloxystrobin, famoxadone and fenamidone. These shifts in sensitivity could only be detected due to the establishment of baseline sensitivities to these fungicides. Subsequent to the registration of group 11 fungicides, boscalid (Frac group 7) was registered for use on potato in 2003 and pyrimethanil (Frac group 9) was registered in 2005 for early blight disease control. Boscalid is a carboxamide fungicide, targeting mitochondiral respiration at complex II (succinate-ubiquinone reductase), as opposed to the complex III site targeted by QoI fungicides. Pyrimethanil is an anilinopyrimidine fungicide targeting methionine biosynthesis. Baseline sensitivities of A. solani to both of these new fungicides were also developed. Both boscalid and pyrimethanil have good intrinsic activity on A. solani with mean EC50 values of baseline populations of 0.69 and 0.043 µg/ml, respectively. However, the baseline for boscalid has considerable variability compared to pyrimethanil. The use of pyrimethanil in rotation with boscalid in areas of high early blight disease pressure may aid in delaying or avoiding the development of resistance to these chemistries.
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1 - North Dakota State University, Plant Pathology, 306 Walster Hall, P.O. Box 5012, Fargo, ND, 58105-5012, USA
2 - North Dakota State University, Plant Pathology, 310 Walster Hall, P.O. Box 5012, Fargo, ND, 58105-5012, USA
Keywords:
Solanum tuberosum.
Session: Poster-9
Location: Ballroom CD/Monona Terrace
Date: Tuesday, July 25th, 2006
Time: 8:00 AM
Abstract ID:245 |
