Key Points: Why replace silage corn? Some regions in Ontario have observed high corn rootworm pressure in 2020 that is challenging current Bt rootworm hybrids. In regions where Bt rootworm corn hybrids have been used for more than three consecutive years, resistance among corn rootworm populations is suspected. Several growers in Ontario are reporting fields with rootworm injury to trait providers and research and extension scientists. Growers in areas with resistant rootworm populations can no longer rely solely on Bt rootworm hybrids for protection against rootworm injury. Continued use of these hybrids in problem fields can perpetuate the issue, allowing resistant populations to survive and spread to neighbouring fields. Other control measures like granular insecticides or seed treatments can only…
