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How to Manage PestsUC Pest Management Guidelines
SYMPTOMSBacterial leaf blight is often first noticed in fields as brown areas about 3 to 4 feet in diameter. Leaf symptoms appear as irregular brown spots, often beginning on the leaf margins. Lesions initially have an irregular, yellow halo and may appear watersoaked. Spots coalesce and cause a leaf blight and dark brown streaks develop on leaf petioles. Floral parts may also be blighted. A sticky amber-colored bacterial exudate, which is a diagnostic sign of the disease, may be present on leaves or observed flowing downward on petioles and flower stalks. COMMENTS ON THE DISEASEXanthomonas campestris pv. carotae is seedborne and survives on and is spread with carrot seed. The bacteria also survives in carrot debris but cannot survive in the soil in the absence of debris. Rain or sprinkler irrigation is required for optimum disease development. Warm weather favors infection and disease development. Optimum temperatures are between 77°F (25°C) and 86°F (30°C); infection does not occur below 65°F (18°C). The pathogen is dispersed in splashing water. Plant-to-plant spread may occur under heavy dew conditions. In most carrot-growing areas bacterial blight does not warrant control. In a few areas, such as the Antelope Valley, severe outbreaks may occur. MANAGEMENTCultural Control
Organically Acceptable Methods
Monitoring and Treatment Decisions
PUBLICATION
UC IPM Pest Management Guidelines: Carrot |
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