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Bacterial
Pustule is caused by Xanthomonas campestris pv glycinea, and
the symptoms are very similar to those of bacterial blight. Symptoms of
bacterial pustule are more pronounced in new leaves than old leaves. Early
symptoms of bacterial pustule are many pale green minute spots on new leaves.
Each spot later has a dark raised pustule on either surface of the leaf. The
pustule at the center is more obvious on the lower surface. In most soybean
areas, bacterial
blight is more common in a growing season than bacterial pustule, which is not
seen in most seasons. Development of this disease
requires high temperatures (85-90° F) and higher than average rainfall. When
rupturing and drying occur, it may be difficult to distinguish this disease from
bacterial blight. Severe infections cause defoliation. The disease overwinters
in infected plant debris and is carried over to some extent on infested seed.
Crop rotation, resistant varieties and burial of crop residues are the most
effective methods of disease control.
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