Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Southern Corn Rust and Possible Stalk Rot – Nematodes

Posted by romeethredge on July 30, 2011

I’ve found Southern Rust in several fields this week. It’s amazing the difference in Southern Rust from year to year. Last year it ate us up, but this year was not a real problem. Here’s some comments from Dr Bob Kemerait, UGA Extension plant pathologist.

“Southern rust is now found in corn across the southern coastal plain of Georgia.  Corn
that is approaching “black layer” is safe.  Corn that
has reached dough stage may be safe.  Earlier than dough stage
and I would suggest that grower look at their yield potential, look through
their field(s) and consider what value a fungicide application could mean to
them.  Late planted corn?  Be prepared for outbreaks of southern
rust.”

Something else we’ve seen this week is bad patches in some corn fields where the stalk and plant went down early and in those patches, the yield drops a lot on yield monitors.  We’re not sure what it is but it has the appearance of fusarium stalk rot.  I flew over thousands of acres of corn in Seminole County yesterday, thanks to pilot Wade Spooner, and the blotches or patches are evident in the field in question. Fortunately, this problem does not show up from the air in very many other fields at this time , see greener field in the other photo. It may be that it’s just not evident yet but we are hopeful that the problem won’t be in all fields.

Here’s some comments about the stalk rot from Dr Bob Kemerait, UGA Extension plant pathologist

“CORN Stalk Rots:   In several south Georgia counties we are seeing UNUSUAL stalk deterioration across wide swaths in the
field.  The lower stalk is simply deteriorating and it is NOT bacterial
stalk rot!  In some instances it seems Fusarium may be involved, in other,
not clear at all.  What IS clear is that yield in areas affected by this
rot (disease or otherwise) drops by up to 80+ bu/A.”             Update on 8-15-2011 – We took nematode samples from this field in the bad areas and high numbers of Southern RootKnot Nematodes were found here , so that is a big part of the yield decreases seen here, apparently.

Area in the center of photo affected, note the dead and some falling stalks. This was a narrow streak that came towards the camera for quite a long ways.

Some affected stalks on left. Good stalks on right were just 10 yards away.

Same field where above photos were taken, note the patchiness. This field will still average very high in yield, but in those bad areas the yield dropped a lot.

Nearby younger field, more green color, can't detect any problem , hopefully there won't be one here. This was the case in most of the fields we saw.

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