STUDIES ON BASELINE SENSITIVITY TO STEROL INHIBITOR AND STROBILURIN FUNGICIDES, AND MONITORING OF FUNGICIDE RESISTANCE IN Marssonina coronaria CAUSING PREMATURE LEAF FALL IN APPLE
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Date
2012
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Abstract
ABSTRACT
Premature leaf fall is one of the most important diseases of apple particularly in
Himachal Pradesh. Present studies were carried out with the objectives to establish baseline
sensitivities of Marssonina coronaria to newly developed sterol inhibitor and strobilurin
fungicides and to monitor the development of fungicide resistance in M. coronaria to some
of the frequently used fungicides in apple orchards of Shimla district of Himachal Pradesh.
The baseline sensitivities were established and observed in terms of mean EC50 values in vitro
(spore germination in presence of different concentrations of test fungicides) against the wild
isolate of M. coronaria. Baseline sensitivity of M. coronaria in terms of EC50 for flusilazole,
hexaconazole and difenoconazole was 0.075, 0.027 and 0.031 mg/l, respectively. For
strobilurin fungicides the mean EC50 value observed for azoxystrobin, kresoxim- methyl and
pyraclostrobin were 0.053, 0.036 and 0.012 mg/l respectively. Five isolates from Shimla
district in Himachal Pradesh (Theog, Kotgarh, Kotkhai, Rohru and Rampur) were selected to
study development of resistance to dodine, mancozeb and carbendazim. The mean EC50 value
for the entire test population of Marssonina coronaria observed was 0.038, 0.237 and 0.096
mg/l for dodine, mancozeb and carbendazim, respectively. The highest Mean Resistance
Factor was observed for carbendazim, i.e. 2.48 followed by mean resistance factor for the
dodine fungicide i.e. 1.56 and least mean resistance factor was observed for mancozeb at
1.15, thereby indicating no development of resistance in M. coronaria to the test fungicides
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Keywords
---, Marssonina coronaria,sterol inhibitor and strobilurin fungicides,apple orchards