Diseases of wheat, oats, barley, Diseases of wheat, oats, barley, and rye diseasesofwheato48boew Year: 1960 88 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 48 fections the entire leaf dries up and turns brown, but the halo usually is distinguishable even on the dead leaf. On the chaff each minute spot of infection is surrounded by a light green to yellowish-green halo; if an entire glume is infected, the tissue between the veins turns yellow and becomes translucent. No bacterial exudate is present on the spots. Life History.—Tests have shown that halo blight bacteria live over winter on the oat
Diseases of wheat, oats, barley, Diseases of wheat, oats, barley, and rye diseasesofwheato48boew Year: 1960 88 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 48 fections the entire leaf dries up and turns brown, but the halo usually is distinguishable even on the dead leaf. On the chaff each minute spot of infection is surrounded by a light green to yellowish-green halo; if an entire glume is infected, the tissue between the veins turns yellow and becomes translucent. No bacterial exudate is present on the spots. Life History.—Tests have shown that halo blight bacteria live over winter on the oat seed and cause infection in the spring on the first leaves. On seed these bacteria are able to remain Fig. .31.—Halo blight of oats. Bacterial infection of oat leaves results in the appearance of yellow-green, oval spots surrounded by clear, trans- lucent hales. alive for at least 2 years, and it seems quite possible that they may live over in the soil and on diseased plant refuse for an equal period. Infection in oat fields shows an increase after rainy periods, indicating that moisture favors development and spread of the disease. Both rain and wind easily may spread the bacteria from plant to plant as well as to different parts of the same plant. Insects play an important part in spreading in- fection by carrying the bacteria from plant to plant. Control.—Since the halo blight bacterium may be carried on the oat seed, in the soil, and on plant refuse, seed treatment, field sanitation, and crop rotation are control measures that should be used. In any area in which losses are heavy, resistant varieties of oats may be useful.
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