In this article we will discuss about the leaf curl of peaches caused by fungi.
Introduction to the Leaf Curl of Peaches:
Although Peach leaf curl disease is worldwide in distribution, it occurs more predominantly in Europe and North America. In India, the disease is prevalent in peach orchards of Kumaon, Kulu and other parts of the Sub- Himalayan range.
Effect of the Disease:
The disease causes much defoliation and distortion of leaves. These generally result in the formation of small fruits or fruit drops, thus reducing life span of the plants.
Symptoms of the Disease:
Symptoms first appear in early spring when the leaves come out of the bud. Some of the leaves appear twisted, puckered, thickened, curled downwards and often greatly distorted.
In some cases, only the lamina is affected but generally the whole leaf gets malformed. Affected leaves are reddish or purplish in the beginning, later turning to reddish yellow or yellowish grey and finally to yellow to brown.
The reddish lamina soon becomes covered with a whitish bloom which represents the fructification of the fungus. Generally this is more conspicuous on the upper surface of the leaf than the lower surface.
Affected diseased leaves fall off prematurely and in serious infections, tree become naked due to premature defoliation of leaves in the early spring itself. Blossoms, young fruits and current year’s twigs also get affected and diseased and fall off prematurely.
Recurrence of the disease every year drains off the vitality of the tree and reduces its life span.
Causal Organism:
This disease is caused by Taphrina deformans (Berk) Tulasne. The fungus is characterised by intercellular sub-cuticular mycelium, absence of fruit body and the asci produced naked on the host surface.
Disease Cycle:
Primary infection takes place through ascospores or blastospores or conidia which are present in the soil of the orchards. Due to rains, these ascospores or blastospores or conidia are washed, splashed or blown onto young tissues where they germinate and cause infection.
At the time of penetration the, germ tube becomes binucleate due to mitotic nuclear division. The binucleate nucleus upon entering the host tissue forms the binucleate mycelium. After the establishment of the infection inside the host, disease develops and symptoms become apparent.
Soon, the asci and ascospores are formed on host surface. Ascospores upon release usually germinate to produce blastospores or conidia.
Secondary infection has not been reported as the fungus can infect only the younger tissues. Older tissues generally become resistant to infection.
Ascospores perennate usually in the fallen infected plant debris in soil. They are also reported to perennate in the bud scales.
Control Measures of the Disease:
(i) Sanitation of the trees and orchards is important in controlling the disease.
(ii) The tree must not have diseased leaves. Therefore, as soon as the disease leaf is noticed, it should be plucked and burnt.
(iii) Fallen infected leaves should be collected and burnt.
(iv) Spraying with lime sulphur or copper fungicides helps in controlling the disease. Among the fungicides, Bordeaux mixture (4: 4: 50), Perenox or Fytolan (0.3%) Blitox-50 (0.25%) are commonly used. One spraying in autumn and another just before opening of the buds considerably reduce the incidence of the disease.
(v) Spraying with Cuman five times a year brings about total control of the disease.