Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Cotton Angular leaf Spot

Posted by romeethredge on July 23, 2015

 COTTON ANGULAR LEAF SPOT (aka bacterial blight):   Angular leaf spot is a bacterial disease caused by the pathogen now known as Xanthomonas axonopodis pv. malvacearum.  We have not seen a major outbreak in many years but are seeing it more frequently this year.   I have seen it in a couple of fields here in Seminole county, and I’ve had reports of it from consultants in Decatur county.

Here’s advice from Dr. Bob Kemerait, UGA Extension Plant Pathology. 

A.  The disease is caused “angular leaf spot”  because the water-soaked lesions are typically defined by the veins of the cotton leaf and take on an angular appearance.

B.  As the lesion develops, it can take on an appearance more like target spot  ( like in second photo below)  but is typically differentiated from target spot because of a yellow halo around the spot and because the initial water-soaked lesion is still discernable in the larger lesion.

C.  Angular leaf spot CAN NOT be managed with a fungicide or anything else applied to the leaf.

D.  While the bacteria can be spread through moisture and splash from irrigation and rain, reducing irrigation is likely to cause more harm to the crop during hot weather than it will help manage the disease.

E.  Angular  leaf spot may produce rapid defoliation of the cotton crop in severe cases.  However, yield losses are not reported to be catastrophic and in a worst-case-scenario may approach 10% (note:  worst-case-scenario).

F. The angular leaf spot found thus far in Georgia has been south of Tift County and west of I-75; it is currently relatively confined.

 

2015 angular leaf spot colquitt county

2015 angular leaf spot colquitt county 2

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One Response to “Cotton Angular leaf Spot”

  1. Samuel Prim said

    It is in eastern Houston County, Alabama, as well.

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