It seems there may not be much of an insect-related silver lining to this season’s spring snowstorms.
Did below-average soil temperatures and unseasonably late snowfall freeze out insects lurking below? Will the bizarre weather patterns prevent migratory pests from moving in? Not so much, says Kelly Estes, agricultural pest survey coordinator.
And in some ways, pest pressure could be worse, she adds. “Whatever populations survived, they are still here. How fast it warms up will determine how fast they emerge,” Estes explains.
Several familiar foes, such as western corn rootworm and Japanese beetles, overwinter in the soil. Bean leaf beetles hang out in wooded areas near fields, waiting for the right time to emerge. “Once they break dormancy, they go to alfalfa and then move to soybeans,” Estes says, adding that soybeans planted early or before corn in 2018 will be a target for bean leaf beetles.
What about the Japanese beetles that pounded crops in 2017, especially in western Illinois? Soil temperatures are likely not quite cold enough to freeze out the populations, Estes says, though she’s not sure how it could play out. “They overwinter into May and then start pupating, so spring really has no impact on them.”
For pests driven by soil temperature, like corn rootworm, most of Illinois is currently eight to 10 growing degree days behind normal. “If we get some warm weather, it won’t take much for the rootworms to catch up,” Estes says, adding that corn rootworm counts increased slightly in 2017. Farmers may also find pockets of Bt resistance. “Corn rootworm are still a big thing for pest pressure in corn,” she says.
Pests on the move
The weather isn’t keeping migratory pests at bay. “The last system came from the North, but we’ll still get systems from the South that will blow this up,” Estes says, adding that black cutworm and armyworm moths moved through Champaign County in early April.
“Usually something is green in fields by now,” she says. “Anything that’s green is going to be really attractive to insects.” Cover crops give armyworms a place to hide, she adds, so make sure termination is complete.
Pests that farmers haven’t seen in a few seasons, like eastern corn borer, could also make a comeback. “We usually don’t see issues with first-generation corn borer, but the late-planted nontransgenic corn will be more attractive for the second generation of corn borer.”
Scout early and often
The same problematic pests linger, Estes says, but the dynamics could bring nontypical pests to the forefront and the usual suspects later. “A lot of this will start to flesh out once we get into the field and see how fast the corn or beans go in,” she notes, adding that May weather patterns will make a big difference.
When crops finally emerge, scout for pests and don’t be “lulled into complacency,” Estes says. Heavy populations of insects such as black cutworm can overpower Bt hybrids. “Later-planted crops tend to be more attractive and more susceptible to insect injury,” she says.
For the latest pest information and insect flight news, follow Estes on Twitter @ILPestSurvey.
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