Target spot severity varies among cotton varieties

From Southeast Farm Press

Target spot has created much concern among cotton growers in the Southeast over the past few years and began showing up in cotton fields in the Carolinas and Virginia for the first time last year.

Little is known about the impact of the fungal disease on yield and quality, but recent research indicates there may be significant differences among varieties.

Target spot has been reported in cotton in Georgia, Alabama and Florida since 2010, but prior to last year had not spread into the Upper Southeast.

Now that the disease has been documented in the region, growers are left to wonder whether target spot is something they should plan for in their varietal selection and cultural practices.

Target spot, technically Corynespora cassicola, began showing up in South Carolina cotton fields in late August last year and in quick order was reported in North Carolina, then on Aug. 26, of last year it was first reported in cotton in Virginia.

Clemson University Plant Pathologist John Mueller says there doesn’t seem to be any distinctive pattern as far as which fields are and which aren’t attacked by the diseases.

“We’ve seen it in fields where we had cotton behind cotton, and in fields where cotton followed two years of corn or one year of peanuts and one year of corn — it’s not just showing up in long cotton rotations, the veteran Clemson plant pathologist says.

Weather last year in South Carolina and most of the Upper Southeast created an ideal environment for the disease pathogen to grow. Cloudy, wet weather over extended periods of time seem to be ideal for the fungus to develop.

North Carolina State University Cotton Specialist Keith Edmisten says target spot first occurred in eastern counties in North Carolina last August. How widespread it was across the state isn’t clear.

“We have other leaf spot diseases (Stemphylium, Alternaria, Cercospera) that we commonly see in North Carolina. These diseases are often associated with dry periods and/or potassium deficiency.

Read the rest at Southeast Farm Press

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