This is in continuation to my previous post on Diseases of apple: Disease Cycle of Premature Leaf Fall. In today’s post we are going to discuss about the Disease Monitoring System for farmers.
The fungus overwinters in the form of apothecia on fallen leaves. Primary infection is caused by ascospores produced on the overwintered leaves. The ascospores discharge begins during spring season but causes infection at a particular leaf age stage.
During first one month after full bloom when temperature generally hovers around 20oC, but humidity is low therefore, leaves are not vulnerable to the infection.
It’s the first fortnight of June when temperature starts rising fast, pre-monsoon showers adds to the humidity in the orchards of shady areas. The infection initiates during this period rapidly and got established in 4-22 days (incubation period).
During second fortnight of June and July the symptoms begin with the response of the host. Less moisture, high humidity/foggy and temperature >20oC initiate blotch and yellowing. Infection near to leaf petiole site initiates early defoliation.
From first week of August onwards when rains recede but temperature remains above 20oC and humidity is above 90 percent, severity of the disease increases to epidemic level. During this period daily prevailing weather like light rains, partially sunny and foggy could predict the most suitable epidemic conditions.
In coming post we shall be discussing about the Management of Premature Leaf Fall disease of apple.