Minnesota's cornfields are facing an age-old nemesis with a modern twist. The battle against corn rootworm beetles has taken an unexpected turn as the northern corn rootworm (NCR) gains ground over its western counterpart (WCR).
Experts Dr. Fei Yang, Extension corn entomologist, and Bruce Potter, Extension IPM specialist, are sounding the alarm about the rise of extended diapause NCR populations, presenting new challenges for corn rootworm management.
Extended diapause - a winter survival trait in NCR eggs - has become a game-changer. These crafty pests delay hatching, staying dormant for two winters, and in rare cases, up to four. This trait gives them an edge in rotated corn fields, leading to increased NCR infestations.
The situation escalated in 2022 when NCR beetles were observed in large numbers across Minnesota. The current year, 2023, remains uncertain due to drought, affecting rootworm injury and lodging. The rise of extended diapause has complicated rootworm management, requiring farmers to evaluate each field's risk individually.
To stay ahead of the rootworm menace, experts advise the following:
Determine your field's risk:
Scouting is essential to assess rootworm populations accurately. Since NCR beetles are highly mobile, more traps per field may be needed. Vigorous hybrids and weed control can help mitigate damage, and at-plant insecticides may be an option for high-risk fields.
Develop a strategy for NCR high-risk fields:
Bt-RW traited hybrids remain effective against many NCR populations but beware of Bt-resistant WCR. Foliar insecticides are an option for adult control, but timing is critical. Introducing an extra year of non-host crops between corn cycles can reduce extended diapause NCR populations.
The areas with extended diapause this year are likely to face problems in 2024 rotated corn. Vigilance is crucial, as overuse of Bt may lead to resistant NCR populations. Reporting fields with extended diapause and NCR problems in Bt-RW corn hybrids can aid in research efforts.
As Minnesota's cornfields brace for the battle ahead, innovative approaches and collaboration between farmers, researchers, and agriculturalists will be key to curbing the rise of these diapause beetles and protecting the heartland's vital corn crops.
Photo Credit: gettyimages-songdech17
Categories: Minnesota, Crops, Corn