Fungicides target hardlock in cotton

A good many South Carolina cotton producers have probably had lots of trouble with hardlock at harvest this year.

Hardlock is when lint in the cotton boll fails to fluff enough to be picked up by the spindles of a picker. When the spindles hit those bolls, the bolls just fall apart and drop to the ground.

Yields can be cut by 15-20 percent in a wet year like this one, according to John Mueller, Clemson University plant pathologist at Edisto Research and Education Center.

“Last year we had a good fall. It was dry and sunny,” says Mueller. “Everything opened and fluffed, and we picked everything we grew.”

Yields exceeded two bales an acre in places last year.

“Hardlock is the reason that, though we grow two bales of cotton, we harvest only a bale and a half,” says Mueller.

He is part of an interstate team with scientists from Florida and Georgia who are looking for solutions to the hardlock problem. Researchers at the University of Florida have theorized that Fusarium verticillioides is a cause.

Damage caused by piercing-sucking insects such as stinkbugs is another.

In the fungus scenario, the Fusarium verticillioides infects the plant through the flower. The solution could be as simple as spraying with a fungicide to protect flowers from the fungus.

Mueller is comparing two different cotton varieties with different growth habits to see how they develop and to see if applying fungicides to them really does have any effect. He uses Paymaster 1218 and Deltapine 555. The 1218 matures earlier than 555 and will be fruiting under different environmental conditions than the 555.

He has used Topsin M and Topsin Flowable at various rates and various timings. “We want to see if there is a yield response, and is it consistent enough to go after labels for these fungicides,” says Mueller. They are all common materials registered for use on many vegetable crops. No fungicides are currently labeled for use on cotton.

If harvest results are positive, a section 18 label will be sought. Stay tuned for the rest of the story.

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