Thursday, October 8, 2015

Apple Disease: Holistic Management of Apple Scab

Reduction of Primary Inoculum:

The primary inoculum of the disease resides in the infected leaves fallen on the orchard floor. These lesions develop into pseudothecia that further develop ascospores that got released in coming spring season and cause primary infection. To reduce the primary infection primary inoculums should be reduced. Thus phytosanitation plays an important role in reducing the primary inoculum. During Oct Nov when 80 per cent leaves have fallen the leaves either should be collected with the help of rake or should be sprayed with 5 percent urea solution. The spray should be directed on orchard floor rather than on the trees. As the nitrogen concentration of 5 percent is required to decompose the fallen leaves that is containing the scab infection and harbouring the fungus for the development of pseudothecia. Since it will decompose faster than the pseudothecia development thereby reducing the primary inoculum of the disease.

Modification of environment:
The disease development requires leaf wetness. The wetness is always affected by relative humidity. Means more the relative humidity slower will be the drying time thus increasing the leaf wetness period. Longer will be the leaf wetness period more severe disease will appear in the orchard. This situation warrants for better sun penetration and air circulation. If we avoid dense canopy and follow proper training and pruning practices we can improve the air circulation and light penetration thereby reducing the chances of scab to appear in the orchard.
Monitored spray control:
             There are two different strategies (curative and eradicative) for monitored sprays, the curative sprays with well timed application of Ergosterol-biosynthesis-inhibiting (EBI) fungicides even after 72 and 96 hour of the predicted infection periods is not only more effective but also economical for control the disease with three lesser sprays.

In coming posts we shall be discussing about the monitored sprays....