What is in this article?:
• Tests across the Southeast have demonstrated that foliar applied fungicides effectively control a number of diseases that frequently hamper cotton plant development.
• Whether controlling theses diseases helps on the bottom line is another question.
Modern varieties different
Modern varieties are different from the older indeterminate cultivars that Southeast growers used a few years back. The length of the flowering period has been reduced in many of the newer varieties. Thus the current varieties produce a larger crop during a shorter period of time.
The correlation between potassium deficiency and mid-season cotton diseases is well documented. Whether 2011 growing conditions will be dramatically different enough to create new stresses and give cotton diseases a better avenue to negatively impact cotton yields will up to Mother Nature.
“In most cases both fungicides controlled diseases and in some cases reduced the amount of materials used to defoliate cotton. The link between fungicides and reduced defoliation has been a random occurrence,” Edmisten says.
Fungicides have also been linked to reduced incidence of hard lock in cotton, but that didn’t happen in the North Carolina tests.
Hard lock occurs when cotton fiber doesn’t fluff out, leaving the boll segments tightly packed together, much like the wedges of an orange.
Although the quality of the cotton fiber may not be severely affected, conventional spindle harvesting equipment is not able to capture the fiber and bring it into the harvester. The hard locked cotton is knocked from the plant and falls to the ground or is strung out of the boll giving the appearance of poor harvesting procedures.
Hard lock is commonly associated with high nitrogen, high plant density, high temperature and high humidity, insect damage, and seed rot. In severe cases of hard lock in the Southeast, conventional cotton pickers can’t pick up the fibers and many times fields are abandoned.
The North Carolina State researchers applied Quadris and Headline at 12 ounces per acre at early bloom on cotton. The same fungicides were applied in two six ounce applications, one at early bloom and one 21 days later. They also used both materials at 6 ounces per acre, applied at early bloom, followed by 12 ounces per acre applied 14-21 days later.
None of the treatments produced a statistical yield difference, compared to check plots. The same lack of difference came up with fiber quality measurements like micronaire and fiber length. Again, no statistical difference, the North Carolina State researcher says.
“Micronaire was the first place I looked for a difference and expected a difference. Keeping leaves healthier longer should have the most direct affect on micronaire, but we didn’t see any significant differences,” Edmisten concludes.