Tar spot of corn has been confirmed in two northern Missouri counties: Holt County in northwestern Missouri and Marion County in northeastern Missouri, as well as in six counties in central Iowa and one in northeastern Kansas.
This is the earliest tar spot has ever been found in the Missouri. The disease was present at a very low incidence and severity in both counties where it was found June 23. Last year, tar spot was not confirmed in Missouri until the last week of August.
Now is the time for growers to scout for the disease and monitor their corn, said Mandy Bish, assistant research professor and state extension specialist in field crop pathology.
“We want to hold off on those fungicide applications a little longer,” Bish cautions. “Treatments at VT through R3 have shown the most consistent results in research on tar spot management.”
When scouting, look for individual stroma or black lesions on leaf surfaces, she said.
“Stroma can be mistaken for insect frass (poop),” said Bish. “Sometimes brown circles or ‘fish eyes’ may surround the lesions. Initially, there will be very few lesions. We have a few previous articles with descriptions, and the Crop Protection Network has many resources on tar spot.”
Bish advises growers to think through some of the known factors that can increase risks of the disease progressing:
- Was tar spot previously confirmed in this field or neighboring fields? The pathogen can survive Missouri winters.
- Is this a corn-following-corn rotation? Corn is the only known host for tar spot.
- Which corn varieties are most vulnerable? (While that information may not be published, seed dealers might have insights.)
Source: farmtalknews.com
Photo Credit: gettyimages-nes
Categories: Missouri, Crops, Corn