New Zealand Plant Protection 66 (2013): 274-283
A survey of 41 apple orchards in Hawke's Bay (25), Nelson (7), Otago (4) and Waikato (5) provided 796 isolates of Venturia inaequalis (black spot or scab), which were tested using an agar plate assay for sensitivity to two demethylation inhibitor (DMI) fungicides (myclobutanil and penconazole) and to dodine. Each fungicide was used at two concentrations to distinguish between highly sensitive, sensitive and resistant isolates. Sensitivity to DMIs in all regions was lower than baseline sensitivity in previous studies, particularly for myclobutanil. Waikato showed significantly lower DMI sensitivity than other regions. Dodine sensitivity was greater than in the 1990s, although Otago isolates were significantly less dodine-sensitive than those from other regions. In a plant inoculation assay to test control by five DMI fungicides of disease caused by resistant isolates, flusilazol and difenoconazole gave significantly better disease control of resistant isolates than myclobutanil, penconazole or fenbuconazole, at standard field rates.
Keywords: fungicide resistance, apple scab, demethylation inhibitor, dodine, resistance management.
 | Apple Futures: New Zealand's low pesticide residue apple production programme J.T.S. Walker, N.M. Park and M.R. Butcher (2015) New Zealand Plant Protection 68: 282-290 |
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| 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 (2014) New Zealand Plant Protection 67: 133-138 |
| Resistance of Venturia inaequalis to quinone outside inhibitor (QoI) fungicides in New Zealand apple orchards S.L.H. Viljanen-Rollinson, S.M. Thompson, S. Keenan, S.R. Bulman, P.J. Wright, P.N. Wood, N.M. Park and R.M. Beresford (2013) New Zealand Plant Protection 66: 284-292 |
| A synthetic agar assay for determining sensitivity of Venturia inaequalis to anilinopyrimidine fungicides in New Zealand apple orchards N.J. Larsen, R.M. Beresford, P.N. Wood, P.J. Wright and B.M. Fisher (2013) New Zealand Plant Protection 66: 293-302 |
| Sensitivity of Venturia inaequalis to myclobutanil, penconazole and dodine in relation to fungicide use in Hawke's Bay apple orchards R.M. Beresford, P.J. Wright, P.N. Wood and N.M. Park (2012) New Zealand Plant Protection 65: 106-113 |
| Sensitivity of Venturia inaequalis and V. pirina to dodine in New Zealand G.R. Bakker (1999) Proceedings of the NZ Plant Protection Conference 52: 167-170 |
| Sensitivity of apple black spot to fenarimol, flusilazol, myclobutanil, penconazole and dodine in New Zealand G.R. Bakker, M.R. Butcher and R.E. Gaunt (1995) Proceedings of the NZ Plant Protection Conference 48: 7-11 |
| Sensitivity of Venturia inaequalis (black spot) on apples to DMI fungicides in New Zealand H.G. Whelan, M.R. Butcher and R.E. Gaunt (1992) Proceedings of the NZ Plant Protection Conference 45: 289-294 |
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