Gummosis of Citrus
- Gummosis and foot rot of citrus is worldwide in distribution
- Attacks more than 200 species of economically important plants.
- Mostly found in tropical countries with high rainfall.
Casual Organism :
Phytophthora palmivora, P. citrophthora , P. hibernalis, P. parasitica, P. nicotianae var. parasitica
Symptoms of Gummosis:
- Primary infection appears at the collar region producing gummy exudation from the lesions of trunk and the crown roots.
- Lesions can girdle the trunk, spread and kill the tree.
- In late stage bark cracks open dries up and fall off exposing the wood for secondary infection by other organism.
- Characteristics symptom is oozing or yellowish or reddish brown gum in large quantities from affected, cracked parts.
- Leaves turn yellow and fall prematurely. Sometime heavy defoliation and gives an indication of tree decline.
- Immature to ripe fruit show water soaked spots.
Disease cycle of gummosis in citrus:
Fungus survives in soil or in old cankers as oospore and chlamydospore. Spores germinate and attack trunk directly or indirectly via zoospore and sporangia. Fungus may enter through lenticles and injuries and begin to penetrate further in the wood in the cambium region.
Heavy soil where drainage impeded high soil moisture, pH 5.4- 7.5 and temperature of 24ºC , high nutritional status, high rainfall and deep planting favors disease.
Management practices of Gummosis of citrus:
- Proper sanitation.
- Availability of drainage facility.
- Tree should be planted in such a way that main lateral roots may not be more than 2 inches below surface of the soil.
- Crop rotation.
- Resistant root stock.
- No injury during grafting program.
- Citrus orchard should be regularly sprayed with Bordeaux mixture (5:5:50) at regular interval.