However, occasionally field corn has been damaged when environmental conditions favor the development and spread of the disease.
Sweet corn is generally more susceptible than field corn.
Common rust can usually be found in corn fields sometime during the growing season, but generally does not appear before tasseling. In those years with exceptionally cool summers, and especially on late-planted fields or sweet corn, yield losses may be expected when the leaves above the ears become severely diseased. Symptoms Common rust of corn can be easily recognized by the development of dark, reddish-brown pustules scattered over both the upper and lower surface of the corn leaves. These pustules may appear on any above ground portion of the plant, but are most abundant on the leaves. Causal Fungus Puccinia sorghi is the fungus causing common rust in corn.