For the most part, the cotton crop in the upper Southeast was “way behind” heading into August. Spring and early summer rains caused root problems, which could set up big problems if rain doesn't continue in August, says Keith Edmisten, North Carolina State University Extension cotton specialist.
Petiole samples urged
Edmisten advises North Carolina cotton growers to take petiole samples of their crop in order to keep up with its nutrient requirements. “Stick to the basics and avoid unproven products,” he says. “Try to keep the crop as early as possible using growth regulators at or before early bloom, pray for timely rains in July and August and a good warm fall. Scout for insects, including stink bugs in Bt cotton.”
In his July 19, 2003 Cotton Insect Newsletter, Mitchell Roof, Clemson University Extension entomologist says scouting will be “vitally important” going into August.
He's had reports of bollworm egg counts of 30 eggs per 100 plants. Some growers had already started spraying for four to six small worms per 100 plants. Moths were showing up in Darlington and Marlboro counties during the same period.
Scouting for bollworms in blooming Bt cotton requires a different technique than in non-Bt cotton, Roof says. Threshold levels in non-Bt cotton are 20 eggs per 100 plants; 75 eggs or 30 small worms in Bt cotton. An escaped worm concept is used in Bt cotton. A worm one-fourth of an inch or larger will probably not be killed or inhibited by further feeding on the toxic plants.
In Bt cotton, worms that are more than one-fourth of an inch or more, spray for three worms per 100 plants or 5 percent damage bolls. Look on the inside of white and pink blooms and two of the smallest bolls per plant to check for bollworms.
Brown stink bugs are starting to move into cotton fields, after being plentiful in corn this season. Roof says so far he hasn't seen many green and southern stink bugs, the most important species in cotton. The green and southern stink bugs generally show up later than browns in cotton.
The aphid populations are beginning to crash in South Carolina, and fungus is showing up, Roof says.