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New Zealand Plant Protection 67 (2014): 133-138

Sensitivity of Neonectria ditissima to carbendazim fungicide in New Zealand

M. Walter, O.D. Stevenson, N.T. Amponsah, R.W.A. Scheper and A.R.G. McLachlan


Carbendazim can be used by New Zealand pipfruit growers for control of European canker, caused by Neonectria ditissima. A total of 162 N. ditissima isolates were tested for carbendazim sensitivity using a mycelial growth assay on amended malt extract agar plates at concentrations from 0-2 mg/litre. Generally, isolates ceased growth at 2 mg/ litre carbendazim, with 65 isolates ceasing growth at 1 mg/litre. The EC50 values calculated for 19 isolates ranged from 0.51 to 1.38 mg/litre. The data suggested that isolates ranged from sensitive (EC50<1 mg/litre) to having intermediate resistance (EC50=1-10 mg/litre carbendazim), based on comparison with other agar-based studies. Resistance in other fungi has been reported at carbendazim concentrations of >100 mg/litre. The isolates tested were mostly sensitive to carbendazim, but some showed a shift towards intermediate resistance. Mycelial growth tests at 2 mg/litre may be a useful tool to screen single spore isolates quickly for potential carbendazim resistance.

Keywords: European canker, Neonectria galligena, Nectria galligena, benzimidazole.

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