Pacific Pests, Pathogens and Weeds

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Summary

• Widespread distribution. On citrus including grapefruit, kumquat, lemon, lime, mandarin, orange, pomelo and tangerine, as well as other genera in the citrus family. An important disease.
• Bacterial spots on both sides of leaves and fruit causing them to fall early. Fruit unsightly. Spots up to 10 mm, with haloes on the leaves. Cankers cause twig dieback.
• Worse on grapefruit, lemon, lime and sweet orange.
• Spreads in wind-driven rain, water splash, and nursery plants. Enters through natural openings, wounds (e.g., leafminers). Survival is in leaf litter, and weeds.
• Cultural control: ensure nursery is canker-free; keep out of orchard when leaves wet; plant windbreaks around and between rows; Valencia orange and mandarin tolerant.
• Chemical control: 2-3 copper fungicide sprays 3 weeks apart, beginning when fruits are about 5 mm diameter.