Agronomic Crop Disease Update – May 22, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Corn
Pythium seedling damping-off as well as Fusarium seedling blight have been diagnosed from several fields that were very wet and the corn took from 10-14 days to emerge. The cool wet weather contributed to the widespread damping-off problem we are seeing. The amount of disease experienced depended on when the corn was planted in relation to the rains. With the warmer temperatures and more normal soil moisture, there should be no problems replanting with treated seed. No additional soil fungicide treatments should be needed if soil moisture is normal at replanting.

Barley
After evaluating the variety trials in all three counties I can report that there are low levels of the spot blotch form of net blotch, scald, and powdery mildew on susceptible varieties. ‘Thoroughbred’ varies in the amount of powdery mildew infection but it has been high overall. Fusarium head blight or scab was also seen on two barley varieties, Nomini and FS 950. The incidence was fairly low (3-5%) and the severity was low as well, maybe only 10-15% of the head was infected. Head scab in barley is a rare occurrence on Delmarva.

 Fusarium head blight on barley

Fusarium head blight on barley.

Wheat
If this weather continues we may have missed a potential scab problem in wheat. So far scab has not been seen. Low levels of powdery mildew and tan spot were seen while evaluating the wheat variety trial.

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