Plant bugs pose major threat to already shrunken cotton crop in Arkansas

Each year plant bugs, a perennial pest of Arkansas cotton, spend June and early July consuming the silk of corn while it’s still green. As seed is set on corn and the silks begin to dry, however, plant bugs begin to gravitate towards other row crops, such as cotton.

This year, the problem is unusually bad.

As with most insects in row crops, there is an established control threshold — the point at which enough insects are attacking a crop that it becomes more profitable to apply pesticides than to simply leave it alone in the field. Gus Lorenz, extension entomologist for the University of Arkansas System Division of Agriculture, said current levels of plant bugs are more than five times the established threshold in many parts of Arkansas.

“Our threshold for plant bugs in cotton is eight bugs per 100 sweeps,” Lorenz said, referring to the practice of scouting a crop and sweeping a large net across the plants. “Right now, it’s not uncommon to see as many as 12-15 per 25 sweeps.”

“It may be one of the highest populations of plant bugs we’ve seen in several years,” he added. “The numbers are extremely high, even in pre-blooming cotton. It may get a lot worse when we get into blooming.”

Bill Robertson, extension cotton agronomist for the Division of Agriculture, said growers and consultants in central Arkansas and elsewhere are keeping a close eye on cotton that borders corn, monitoring the movement of plant bugs from the latter to the former and their effect on “square retention” — the proportion of flower buds retained by the plant — and fruit damage.

“Many growers have done a good job of maintaining square retention, pre-flower, so far this season,” Robertson said. “The problem is that the invasion can sneak up on a grower. You’ve got a whole wave of adults coming in that haven’t been exposed to previous pesticide applications. It’s something that will sneak up on you and you’ll lose control if you’re not careful.”

Both Lorenz and Robertson emphasized the importance of scouting cotton multiple times a week over the next several weeks.

“Corn’s at that stage where the silks are drying down, and we’ve got a ton of corn out there,” Robertson said. “We’ve had a couple of cooler days that might have helped keep the corn silks green, but now that it’s turning really hot, the corn silks are drying down, so there’s this mass exodus of plant bugs. This year, Gus (Lorenz) is seeing them moving in higher numbers than normal.”

Early- to mid-July is typically a busy time for Arkansas cotton growers. In addition to pest management, growers are trying to put out their final applications of fertilizer and getting their lay-by applications of herbicides in place to set the stage for irrigation.

“I’ve always heard we’re never more than 10 days away from a drought in Arkansas,” Robertson said. “But with our late-planted — and even later-maturing — cotton crop this year, coupled with a poor root system, it may be more like seven days away from a drought this year. Everything’s really critical right now, in terms of timing, to not let go of any yield potential, as we may be headed toward a year with only average yields.”

The plant bug danger is just another hurdle facing cotton farmers this year. Arkansas growers planted significantly fewer cotton acres in 2021, falling from about 525,000 acres of upland cotton in 2020 to about 410,000 acres in 2021. Nationally, upland cotton acres fell from about 11.9 million acres to about 11.6 million acres this year.

Higher corn and soybean prices during planting caused cotton acres to drop.