Citrus Canker Control

Symptoms

Caused by the bacterium Xanthomonas. Raised, corky, brown scabby spots with a yellow halo and an often water soaked margin appear on leaves, twigs and fruit. Spots can crack and become rough. Severe infection causes leaf drop, twig dieback, and blemished fruit that is unfit for sale.

Damage

Citrus canker disfigures fruit, lowering its grade and market price, and weakens trees through repeated leaf and twig damage. It spreads fast by rain splash, wind driven rain, and on tools and the leaf miner pest. Young trees and acid lime are highly susceptible and can suffer serious yield and quality loss.

Organic & cultural control

Use disease free certified saplings and resistant or tolerant types where possible. Prune and burn cankered twigs in the dry season and avoid working in the orchard when foliage is wet, which spreads bacteria. Provide a windbreak to reduce wind driven rain, control the citrus leaf miner whose tunnels open the way for infection, and disinfect tools between trees.

Chemical control

Protective sprays of copper based bactericides such as copper oxychloride, often combined with controlling the leaf miner, reduce new infection, applied before and during the rainy flush periods; some programmes add a recommended antibiotic such as streptomycin under guidance. Always read and follow the label, observe the pre-harvest interval, and consult your KVK or agronomist before spraying.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Start with clean certified nursery stock and choose tolerant varieties. Establish windbreaks, since wind driven rain forces bacteria into leaf pores. Keep tools and footwear clean between blocks, manage the citrus leaf miner, prune in dry weather, and remove fallen infected leaves and fruit to lower the bacterial load.