Nature is amazing in what it can accomplish and that includes bringing southern insects to the north each growing season.
When a low-pressure system moves across North America from the west, and there is a high-pressure system in the east, moist air from the Gulf of Mexico is sometimes pumped north through the continent.
Insects hitch a ride north on that moist air and they drop down on the backsides of thunderstorms.
This is how black cutworms, armyworms, potato leafhoppers, aster leafhoppers, some small green aphids, and cereal aphids wind up infesting crops in the north.
“We’ve already seen some black cutworms and armyworms in our traps this year,” said Bruce Potter, University of Minnesota IPM specialist in Lamberton. “We’ve had a couple of those events with black cutworm, not a horribly big year for the insect, but from April 28 to May 1 we had a system that brought significant captures into parts of Minnesota.”
Potter spoke at the May 11 Field Notes webinar.
“We know that when insects have arrived, we can start using growing degree day models to predict when eggs will hatch…when cut worms are big enough to cut corn, when they should be ready to pupate, and when the risk starts to go down.”
Typically, the southern insects land in Iowa and southern Minnesota before making their way north, he said.
“We get migrations in northwest Minnesota, but those tend to happen later in the spring than those in southern Minnesota,” he said.
One factor affecting insects is the current La Nina climate, said Dennis Todey, USDA Midwest Climate Hub director.
“What we’re talking about with La Nina is sea surface temperatures in the Pacific Ocean,” he said, speaking during the Field Notes webinar. “We are still in a full-fledged La Nina. Typically, La Ninas are a wintertime phenomenon, and tend to weaken in the summertime, but when they happen during the spring and summer, they do have some influence.”
The Upper Midwest experienced very cold temperatures and cloudiness through April and into early May, he said. There wasn’t a lot of rain, but the clouds and cold temperatures kept the soil moist. There’s also been a lot of wind.
As of May 11, corn planting progress was the second-slowest since 2000 in the Upper Midwest – only behind 2013. Todey pointed out, though, that 2019 planting progress eventually became slower than 2013 because of excessive rain. Eventually, farmers were able to plant in 2013, while there were ultimately many fields of prevent planting in 2019. Todey thinks 2022 is more like 2013.
“I think we are going to be able to make some quicker progress going along here, too,” he said.
He forecast some very hot temperatures in the 90s yet in mid-May – and asks Midwesterners to take care when the weather becomes so much hotter so quickly. Livestock can also be severely affected and need access to water and shade.
Todey added that the northern U.S. had a slightly better chance for cool and rainy weather in late May.
For June, July, and August, he said the models suggest warmer-than-normal and dry conditions for the Great Plains and the Upper Midwest.
Field Notes are offered each Wednesday from 8-8:30 a.m., May 25-Aug. 31. To learn more, e-mail [email protected] or visit https://extension.umn.edu/courses-and-events/strategic-farming-field-notes to register. Field Notes is brought to the public by University of Minnesota Extension, and supported by the Minnesota Corn Research & Promotion Council and the Minnesota Soybean Research & Promotion Council.
