Symptoms and Signs
Individual leaves affected by sour skin wilt and die back. Internally, leaves develop a soft, watery rot. The fleshy scales associated with infected leaves rot to form a tan-colored slimy ring in the bulb. Adjacent rings may remain healthy. The neck of infected bulbs is soft when pressed.
Comments on the Disease
Sour skin occurs on both onion and garlic, but usually is only a concern on onion. The pathogen, which survives in the soil, is splashed onto leaves and into the neck of the onion during rain or overhead irrigation. The bacteria gain entrance through wounds and watersoaked tissue. Once in a leaf, bacteria continue to grow down the blade into the bulb. Warm weather favors disease development; optimum temperatures for disease development are over 85°F.
Switch from sprinkler to furrow irrigation once onions start to bulb (bulbing occurs about the time the bulb is twice the diameter of the neck). Make sure onion tops are well matured before harvesting. Provide for quick drying following topping, especially if temperatures are high.