Heat and drought followed by rain bring constant challenges to the Louisiana and Arkansas cotton crops. Most of the cotton crop in Louisiana and Arkansas got off to a good start this year, because we had sufficient spring rainfall in most parishes and counties and a warm spell in late March and early April.
May temperatures actually dropped, especially at night, dramatically slowing overall growth and leaving seedling and young cotton vulnerable to intensive thrips pressure.
Warmer daytime and nighttime temperatures finally returned, but without the periodic rainfall needed to continue advancing the crop. As a result, many producers are managing a cotton crop that is very short in stature.
The intense heat rapidly built heat units and that, combined with the lack of soil moisture, stressed the cotton, which has responded in many cases by forming 4-bract squares. We observed 4-bract square formation last year under similar heat stress, but the problem was not observed until mid-July.
The main concern is that almost all of the malformed squares will abort and shed, and there is not much that can be done about it. Rogers Leonard of the LSU AgCenter has observed this situation in several fields already, and does not believe that the square shed is due to insect pest pressure.
The damage was done over 20 days ago, very early in the formation of the squares as a plant physiological response, and growers are just now seeing the results.
The recent rains brought welcome relief to many dryland cotton fields that had not had precipitation in many weeks, and a respite to producers that were forced to start irrigating cotton much earlier than they would like.
Most of the major cotton-producing areas experienced 1 to 4 inches of rain last week.
Many producers may want to rush out and finally apply the plant growth regulator they have been holding back on for fear of forcing the crop into cutout. “After all,” the thinking goes, “all that nitrogen has been sitting in the soil unused by the plant, and surely we can anticipate rapid vegetative growth.”
However, the overall crop is shorter in stature than it should be right now, and many producers are counting only seven to eight nodes above white flower, when it should be 10 or greater at this stage. As a result, growers may want to refrain from applying PGRs too quickly or too heavily.
Roger noted, “We need to strike a balance between vegetative and reproductive growth for this cotton crop. This current square shed may result in a gap of bolls in the plant as the season progresses. Assuming we continue to get periodic rainfall, the top crop may make up for this initial loss.”