Delayed Planting Alters Pest Pressure
Planting date and weather may compound insect issues
Independent crop consultant Joel Moor is working with his growers to handle the multitude of challenges endured thus far in 2021
A combination of unfortunate circumstances could mean Mid-South cotton growers will have to deal with a buggier-than-normal season that lasts through the late summer and into early fall.
Extended periods of frozen winter weather made many hopeful for a light bug year in 2021. However, frigid temperatures didn’t slow down yield-robbing pests, like the especially hardy tarnished plant bug, and it may have harmed some of the beneficial insects depended on for additional control.
Adding insult to injury, an unusually cool, wet spring delayed planting for many cotton growers, which sets up a scenario for increased in-season insect pressure when the crop is highly susceptible. Then, widespread flooding in mid-June further challenged Delta growers.
“We are looking at late-planted or replanted cotton in much of the Mid-South, and much of the emerged cotton endured cold temperatures, some sandblasting and excessive rainfall. That amplifies insect damage and sets us up to catch that additional late-season pest flight,” says Joel Moor, Mississippi independent crop consultant.
Planting dates can have a substantial effect on insect pressure. Early planted cotton may escape a late-season flight of pests because it has reached a growth stage were worm and insect pressure, if not extreme, will no longer affect yield. Late-planted cotton, however, often experiences the opposite scenario.
In a year like this one, Moor begins the season with an insecticide over-treatment in addition to normally recommended seed treatments to help control early season thrips.
“Thrips pressure begins shortly after the cotton comes out of the ground,” he says. “We haven’t had to spray yet with the over-treatment at planting. Depending on conditions, though, we might spray for thrips, especially if continued cold weather slows down plant growth.”
Once cotton begins squaring, Moor turns his attention to aphids and the tarnished plant bug.
He makes his first targeted spray when tarnished plant bug numbers exceed 8% of the total pest count per 50 sweeps.
“We are focused on square retention. We need to ensure we set those first fruit, because those cotton bolls on the bottom part of the plant are your money bolls,” Moor says. “I prefer sticking to a lower tarnished plant bug threshold to prevent puncture feeding on fruit development. They can pop the squares.”
Knowing there will be multiple insecticide sprays per season, especially in a year like 2021, Moor recommends rotating modes of action to minimize resistance development.
“We try to mix it up, and we rarely use only one product,” Moor says.
Early on, during the first couple weeks of squaring and early bloom, his tank-mix recommendation usually includes two shots of acephate, Diamond insecticide and Transform® WG insecticide with Isoclast® active. As the season progresses, depending on pest pressure and growth stage, he may come back with another shot of acephate and Transform.
“Plant bugs are a season-long, every 10-day deal in cotton. Left uncontrolled, tarnished plant bug would decrease yield tremendously, especially in a year with heavy infestations,” he says. “Pressure varies from year to year and there doesn’t seem to have any rhyme or reason to it.”
“What we do know is that tarnished plant bug has numerous preferred hosts,” Moor says. “If someone missed controlling pigweed or marestail, you’ll often see those weeds completely covered with plant bugs. To help with insect control, we’ll try to keep fields and nearby areas as free of weeds as possible.”
As the season progresses, Moor may recommend a late-season tank-mix treatment of acephate and bifenthrin, and possibly a pyrethroid, depending on resistance development and crop growth stage.
“You have some top bolls you’d like to save, but what’s in the top may not pay for an insecticide application,” he adds.
Discover how Transform can help you control tough cotton pests this season.
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