Also known as black chaff, bacterial streak
Xanthomonas campestris pv. translucens (Jones et al. 1917) Dye 1978
- Symptoms: Black chaff and bacterial stripe are both caused by the same organism; the site and extent of the symptoms depends on the strain of the bacterium, the affected cultivar and environmental conditions. Black chaff occurs primarily on the glumes (picture at top left); “bacterial stripe" occurs primarily on the leaves and/or leaf sheaths (picture at bottom left). Initial symptoms are narrow chlorotic lesions or stripes that have a watersoaked appearance; droplets of sticky yellowish exudate may appear with extended periods of rain or dew (picture at right). The exudate dries to form crusty droplets or a translucent film on the surface of affected tissues. The film may crack and give a scaly appearance. If infection occurs early in the crop cycle, the spike may be infected; resulting in sterility; when the disease is severe, entire leaves or spikes may be killed.
- Development: The bacterium can be seed borne and persists on crop residues in the soil, tolerating warm as well as freezing temperatures. Free moisture is required for infection and spread of the disease. Infection occurs through stomata and broken epidermal tissue. The disease is spread by splashing rain, plant contact, and insects.
- Hosts/Distribution: These diseases occur worldwide on all small grain cereals and many grasses.
- Importance: Black chaff and bacterial stripe rarely cause significant damage, even though symptoms often may be extensive.
