Citrus canker infested by Bacterium Xanthomonas
In India, citrus canker is endemic and occurs in all the citrus growing states.
It is highly affected in Telangana, Tamil Nadu, Andhra Pradesh, Karnataka,
Rajasthan, Madhya Pradesh, Assam,
Conditions favour for infestation
Citrus canker is a citrus disease caused by the bacterium Xanthomonas axonopodis. While not harmful to humans, canker significantly affects the vitality of citrus trees, causing leaves and fruit to drop prematurely. A fruit infected with canker is safe to eat, but has reduced marketability as fresh fruit.
The bacteria that cause citrus canker enter leaves through stomata, or through wounds caused by weather damage or insects, such as the citrus leaf miner (Phyllocnistis citrella). Young leaves are the most susceptible. Symptoms generally appear within 14 days of exposure to the canker bacteria. The bacteria remain viable in old lesions and on plant surfaces for several months.Canker lesions ooze bacterial cells, which can be dispersed by wind and rain. Infection may spread further by heavy rain and wind events such as hurricanes. People can move the disease by moving contaminated equipment and tools, tree clippings, untreated infected fruit, and infected plants. The disease thrives in areas with high rainfall and high temperatures. Citrus species, such as grapefruit, lime and lemon, are most susceptible to citrus canker.
Symptoms
The disease causes small, round blister-like formations on leaves, branches, stems, new shoots and fruit. The canker lesions can develop within seven days of infection on leaves. Fruit are susceptible up to 90 days after petal fall. Young plants and seedlings are more susceptible to Citrus canker.
Symptoms
- On leafs
Bright yellow spots on the underside of the leaf occur first followed by raised brownish lesions on both sides of the leaves. These then become rough, cracked and corky. The canker may be surrounded by a water-soaked yellow or chlorotic halo.
- on fruits
Crater-like lesions form on the surface surrounded by an oily, water-soaked margin or yellow halo, which can expand to 10mm. They may be scattered or several lesions can occur together in an irregular pattern. In young fruit an ooze of resinous substance may be observed.
- On stems and branches
Lesions are light to dark brown, raised and corky, that eventually become dry and scabby. They can vary in size from 5 to 10mm. The appearance of symptoms on stems often indicates infection for a long time.
Spread
The canker lesions ooze bacteria when wet, which can infect new growth, and be dispersed over short distances through wind, rain splash and overhead irrigation.
Long distance spread can occur through flooding and cyclones, and human assisted movement of clothes, equipment and infected plant material (including budwood, rootstock seedling, budded trees).
Plants are infected when bacteria or bacteria spores enter wounds and natural openings on leaves, growing shoots and fruit. The disease can be spread by birds, insects and humans, particularly when trees are wet.
- In leaves lesions are surrounded by yellow Hallow
- But in fruits lesions are not surrounded by yellow hallows
- Due to lesions on fruit skin it can decline the market value
- Symptoms on leaves in sever conditions heavy defoliations take place
- Bacterium can be survive on plants for 6 months
- And spread through dispersal and also rain splashs
- And also leaf miners
Citrus canker Control measures
Regular spraying of antibiotic and copper oxy chloride
Select the resistance varieties
Tenali and balaji
Blitox – ( Copper-Oxy-Chloride )
Dosage : 3gms/1ltre
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Streptocycline – ( antibiotic )
Dosage : 1 gm/ 1ltre
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