ISHS Acta Horticulturae 662: VII International Symposium on Temperate Zone Fruits in the Tropics and Subtropics
OUT-BREAK OF MARSSONINA BLOTCH IN WARMER CLIMATES CAUSING PREMATURE LEAF FALL PROBLEM OF APPLE AND ITS MANAGEMENT |
| Authors: | J.N. Sharma, A. Sharma, P. Sharma |
| Keywords: | premature leaf fall, Marssonina Blotch, apple |
| Abstract:
A new problem of mid-season defoliation in apple was noticed in 1992 in some of the orchards in Kotkhai area in Himachal Pradesh. It appeared in epidemic proportions during 1995 in as many as 90 per cent of the apple orchards in the state covering more than 70,000 ha. The unusual leaf drop started in late summer months after the onset of rains and apple fruits nearing maturity were commonly seen hanging from the defoliated branches. Systematic investigation revealed that the early leaf drop in apple was due to a hitherto unknown fungal disease - Marssonina blotch caused by Marssonina coronaria (Ell. et J.J. Davis) J.J. Davis Syn. Marssonina mali (P. Henn.) Ito. Disease symptoms are visible invariably after the rains in spring and early summer months as 5-10 mm diameter dark brown spots on the mature whorl leaves, which turn yellow and drop within a few weeks. Small dot-like structures (acervuli) are also visible in such lesions. The fungus also attacks the fruit by causing circular dark brown spots of varying size (3-5 mm diameter) on all the commercial cultivars, thereby downgrading the quality of the marketable produce. This disease favoured by high rainfall and moderate temperature ranging from 20-22°C during the fruit development stages of apple. Protective sprays of mancozeb (0.3%), copper oxychlordide (0.3%), zineb (0.3%), ziram (0.3%) and HM 34.25 SL (0.25%), dodine (0.075%) and dithianon (0.05%, provided complete disease control in the field. | |
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