Where boll weevils and worms once ruled, a ragtag bunch of secondary pests now vie for dominance. A war based on power and force just doesn't seem to work against these guerrilla fighters
But consultants and cotton producers are adjusting scouting methods for the hit and run tactics of these so-called secondary pests, giving more attention to signs of feeding, in addition to visual sightings.
“On plant bugs, we've always run sweep nets and drop cloths, but a lot of our consultants are adding square retention techniques as a way to monitor secondary pests,” according to Craig Massey, University of Tennessee Extension area specialist.
“Anytime square retention drops below 80 percent to 85 percent, we know we need to tighten things up,” he said. “We can get damage if there is a multi-pest situation out there. If we're bumping along at 95 percent, we're in pretty good shape. The plant won't hold all that fruit anyway in our region.
“On stinkbugs, we're still doing our drop cloths, but we're also doing boll counts. We're also looking at traps for stinkbugs, but they attract more brown stinkbugs than the green and the green is more predominate in west Tennessee.”
Massey advises consultants or growers to cover the entire field when scouting for stinkbugs. “They will feed in isolated areas,” he says. “You may miss them.”
As for control of stinkbugs, “most of the time, we can do a real good job with pyrethroids on the greens. If we have a real high population that needs to be knocked down, or we start seeing some browns in there, we'll go with an organophosphate.”
For plant bugs, “Centric and Trimax are both good materials that are best used in a systems approach,” noted Massey. “We can go in at matchhead square and band over the top of the cotton. We can come back and do that again and build up the chemical in the plant.
“If I have some high populations of plant bugs and my square retention is down, I'm going to use something to knock them down quickly.”
“The key to scouting, no matter what the pest, is to get in the fields two to three times a week and watch for changing patterns,” noted Somerville, Tenn., crop consultant Len Doyle.
“We start scouting during the first two weeks of squaring, going with a threshold of 7.5 plant bugs per 100 sweeps of the net,” he said.
Between the third week of squaring and first bloom, they employ a two-stage scouting program.
First, they sweep for adults, adhering to a treatment threshold of 15 bugs per 100 sweeps. They also begin using a drop cloth to count larvae and nymphs, watching for a threshold of two bugs per 6 feet of row.
Doyle augments captures with visual inspection of fields and individual plants.
“We don't let our square retention drop below 80. If we see a pattern developing over two to three days, and the retention is dropping, we're going to spray.”
Scott Stewart, cotton insect specialist at University of Tennessee's West Tennessee Experiment Station in Jackson, Tenn. added that plant bug scouting often becomes more difficult later in the season. “When you have adult and nymph populations, visual scouting is difficult, sweep nets are only good at collecting adults and square retention isn't as reliable anymore because the plant is naturally senescing fruit.”
Stewart suggests looking for dirty blooms, which indicates that a square has been fed upon. “If you see those types of things more frequently, you know you need to start looking for plant bugs. The good thing is the plant can tolerate a few more plant bugs as the season progresses.”
The Doyles point out that if a plant bug has been feeding on a square, “you can squeeze it and get a milky secretion,” Len said. “If it's a natural shed, it's dry and crunchy.”