Diseases of Fruit Plantation Medicinal and Aromatic Crops

Pacific coast pear rust

Causal organism:Gymnosporangium libocedri
Symptoms

• Leaf: Spots on the leaf fade and darken as the leaf matures or falls from the tree. Green shoots and leaves are also attacked but not so frequently.
• Fruit: Pear fruits are malformed while young and drop from the tree. Bright yellow to orange spots with numerous cup-shaped pustules (aecia) develop over the fruit surface. Oriental and european cultivars are susceptible. ‘Winter Nelis’ is severely infected where as ‘Bartlett’ is resistant.
• Rust pustules (uredia) observable on flowering pear leaves (Pyrus calleryana).
• Dissemination : Spores produced on eastern red cedar are discharged following rains, and further disseminated by wind currents to pear plants. Spores produced on pear may also be carried by wind to cedar trees.
• Primary source of inoculum: Ttelial galls on cedar plants bearing air borne basidiopsores.
• Secondary source of inoculum: Airborne basidiospores





Management

• Cultural control
• Remove alternate hosts growing all around the orchard.
• The grower should be concerned about occurrence of Cedar pear rust when susceptible cultivars like eastern red cedars in the vicinity accompanied by numerous rainy periods during spring.
• Sources of infection may be reduced by cutting and removing the nearby eastern red cedars. It is difficult to completely eliminate sources of infection due to the presence of wind borne .Some pear cultivars are resistant to cedar pear rust, which can be grown without fungicidal sprays for its control.
• Chemical Method
• Certain fungicides used for controlling scab disease may also control cedar pear rust. Mancozeb spray 2 ml / lit water has been found effective.