By Alison Robertson
Bacterial leaf streak is a new disease of corn that was confirmed in the U.S. last year - as if we don't have enough spots to diagnose on corn! And, as you might expect, a lot of spots and streaks on corn can be misdiagnosed for bacterial leaf streak.
Over the winter, corn pathologists across the U.S. worked together on a publication about bacterial leaf streak. This publication also compares several "lookalikes" with bacterial leaf streak. You can view the publication or download a pdf copy here.
Below are some images I have received over the past week related to bacterial leaf streak (Figure 1A-D).
Figure 1. Bacterial leaf streak "lookalikes"
A. Possibly bacterial leaf streak - although it may be sunscald. to be 100% sure we would need to check this in a crop diagnostic clinic.
B. "Streaks" are too white to be a disease. Probably abiotic damage, e.g., the leaf folding back and forth in the wind
C. Sunscald - again the "lesions" are too white.
D. Lesion mimic - this is a genetic disorder that occurs on some hybrids, particularly when conditions are stressful.
Here's another lookalike - corn leaf blotch miner feeding (Figure 2).
Figure 2. If you hold this leaf up to the light, you should be able to see the windowpane effect caused by corn leaf blotch miner.
This image below depicts bacterial leaf streak symptoms well (Figure 3). The disease on most of this leaf is severe and many of the streaks have coalesced so they are difficult to see. Note the inset that shows the reddish brown streaky lesions with the bright yellow halo extending from the lesions.
Figure 3. Characteristic symptoms of bacterial leaf streak.