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Bacterial Spot

Bacterial Spot

Xanthomonas spp.

bacteria

In a Nutshell

    Small, yellow-green lesions appear on young leavesLeaves are deformed and twistedDark, water-soaked lesions on older foliage

Hosts: %1$s

· Capsicum & Chili · Tomato

Symptoms

The first symptoms are small, yellow-green lesions on young leaves, which usually appear deformed and twisted. On older foliage, lesions are rather angular, dark-green, and greasy in appearance, often surrounded by yellow circles. They are often more numerous on leaf margins or tips. Eventually, the spots look like shot holes because the center dries up and disintegrates. Fruit spots (up to 0.5 cm) start off as pale-green, water-soaked areas, which eventually roughen, becoming brown and scabbed.

Trigger

Bacterial spot occurs worldwide and is one of the most devastating diseases on pepper and tomatoes grown in warm, moist environments. The pathogen can survive in association with seed, either externally or internally as well as on specific weeds and later spreads through rain or overhead irrigation. It enters the plant through leaf pores and wounds. Optimum temperatures range from 25 to 30°C. Once the crop is infected, the disease is very difficult to control and can lead to total crop losses.

Biological Control

Bacterial Spot is very difficult and expensive to treat - if the disease occurs early in the season, consider destroying the entire crop. Copper-containing bactericides provide a protective cover on foliage and fruit. Bacterial viruses (bacteriophages) that specifically kill the bacteria are available. Submerge seeds for one minute in 1.3% sodium hypochlorite or in hot water (50°C) for 25 minutes.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Treatments with copper plus mancozeb are more effective than treatment with copper-based products alone.

Preventive Measures

    Plant certified disease-free seedsUse resistant varietiesInspect, remove and burn any seedling with leaf spotsRemove weeds in and around the fieldMulch around plants helps to avoid soil to plant contaminationCrop rotation of 2-3 years is recommendedAvoid overhead irrigation and working in fields when foliage is wetPlow in or remove plant debris after harvestClean tools and equipment