Symptoms
Raised corky brown lesions surrounded by a yellow halo on leaves, stems and fruit. Severe infection causes premature leaf and fruit drop and dieback of young twigs.
Prevention
Plant certified disease-free stock and use windbreaks (wind-driven rain spreads the bacterium). Disinfect pruning tools and avoid working among trees when wet.
Treatment
Organic
Prune and burn infected twigs during dry weather. Apply copper-based bactericide on a protective schedule, especially after storms.
Chemical (last resort)
Apply copper hydroxide or copper oxychloride sprays at flushing and after wet periods. There is no curative chemical; copper is protective only — observe PHI.
Affects 3 crops
Sources
MARDI Citrus Production Guide; DOA Plant Quarantine Bulletin