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October 9, 2020
FORAGE OPTIONS TO REPLACE SILAGE CORN
• Rotating out of corn is the most effective way to reduce populations of Bt-resistant corn rootworm.
• To replace silage corn for 2021, establish fall rye or winter triticale immediately after 2020 silage corn harvest.
• After the cereal silage comes off in mid-May, establish sorghum-sudangrass and take two cuts.
• An energy source will need to be supplemented; producers should consult their nutritionist to correctly balance the ration.
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 provide root protection in low to moderate populations; they do not reduce rootworm populations.
The best management practice to reduce the resistant rootworm population is to rotate out of corn for at least one year. Corn rootworm beetles typically lay their eggs in corn fields. If that field is rotated to a non-host crop (e.g. alfalfa, rye, triticale, sorghum-sudangrass) in the following year, the larvae will die after hatching, and the population will be eliminated.
Growers are encouraged to use alternative forage options to replace silage corn for a minimum of one year, but ideally for the next two to three years.
For entire article visit https://fieldcropnews.com/2020/08/forage-options-to-replace-silage-corn.
Written by OMAFRA forage and grazing specialist Christine O’Reilly