Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Cotton Disease a Problem

Posted by romeethredge on July 30, 2011

We are seeing spots appear on cotton leaves, bracts and bolls, and we are worried about whether it will affect yield.  It seems worse where we have recieved more rain , where cotton is well irrigated , on a little heavier soils, on cotton after cotton , and where it’s occured in the past.  There are many types of leafspots on cotton, some related to potassium in the plant, but we have isolated corynespora leaf spot from several samples.

Here are Dr Bob Kemerait’s, UGA Extension Scientist, comments.

Changing weather patterns over the past week with increased rainfall have created
conditions much more favorable for development and spread of fungal diseases.

COTTON:
We are getting cotton leaves with spots; many of which are diagnosed as “Corynespora leaf spot”.
As you know, it is my belief that a) this disease can cause significant
premature defoliation in a field and b) can be managed with a fungicide based
upon very limited data.  THEREFORE:  I do not recommend
that each and every field where Corynespora leaf spot has been found needs
to be treated with a fungicide!  However, where the disease has been
severe in the past, where rotation is short, where the disease appears to
be progressing beyond a few incidental spots, the grower may want to
consider treating some part of the field with a fungicide like Headline,
Twinline, or Quadris.

The above 3 photos show some of the spotting we are seeing in cotton this week from various causes.

Farmer Brad Thompson and Consultant Wes Briggs and I are checking out some good looking fruited up cotton that has leafspot and spots on bracts and bolls. This field has recieved more that it's share of showers lately keeping leaves wet, a recipe for fungal infection.

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