End of Season Cotton Management Decisions for Fields Infected with Bacterial Blight

By: Tom Allen and Darrin Dodds

Angular leaf spots attributed to bacterial blight of cotton.

Since the middle of July, numerous fields have been confirmed to have cotton plants infected with the bacterium that causes bacterial blight.  The majority of the cotton fields were contained within a few counties in the Delta (Bolivar, Coahoma, Leflore, Quitman, Sunflower, Tallahatchie, Washington), and a low number of exceptions outside of the Delta (Calhoun, Grenada, Monroe, Yalobusha).  The organism that causes bacterial blight has the potential to overwinter on cotton stubble left standing in the field.  However, this was likely not a source of inoculum for the infection that occurred over such a large area in 2011 since several of the infected fields were not in cotton in 2010 or had not had cotton grown in them for a period of at least 5 years and one field in particular had never had cotton planted as a crop.

To limit the risk of an infection occurring next season in a field where bacterial blight was confirmed during 2011there are a few important options to consider:

1)  Plant something other than cotton in the field in question.

2)  Plant a variety with confirmed resistance (see “2011 Cotton Bacterial Blight Trial Ratings: Stoneville, MS” for information regarding varieties shown to be resistant to the bacterium).

3)  Tillage – to include subsoiling and discing.

The economics of the situation may dictate the best option from the list above but this will differ from farm to farm.  Probably the best option is to shred stalks in fields with known bacterial blight infection and incorporate the stubble into the soil.  The vast majority of the literature regarding bacterial blight suggests the bacterium has trouble surviving in the soil profile since competition from other organisms is increased.  In situations where stubble remains in the field the bacterium can survive for periods of time between 3 and 5 months depending on the environment even in situations where the plant material has been dry for an extended period of time.  However, in situations where cotton will be planted next season plant material in fields where bacterial blight occurred incorporated into soil will be the most beneficial solution.