After a good start, wet conditions stalled planting across much of the state. Dr. Debalin Sarangi, Extension weed scientist, and Bruce Potter, Integrated Pest Management specialist at the Southwest Research and Outreach Center by Lamberton discussed weed and insect management challenges faced by growers this year due to an extended planting season during the May 8 Strategic Farming: Field Notes session.
Weed management updates: Preemergence (PRE) herbicides are the foundation of a strong weed management program, regardless of the postemergence (POST) program used. Typically a quarter to a half inch of rainfall is needed to activate PRE herbicides, so activation should not be an issue this year for products already applied.
The bigger question this year from growers who have been able to plant and apply a PRE earlier this season, is how long will their PRE herbicide last? Dr. Sarangi reports that residual activity typically lasts three to four weeks after application, so where crops were planted mid-April, these products may be running out of steam.
It will be some time until crops reach canopy closure so check fields for weed emergence and prepare to apply POST products early. The addition of a PRE herbicide to your POST applications will help extend herbicide residual activity for troublesome weeds like waterhemp.
Insect management updates: Bruce Potter is leading the black cutworm (BCW) monitoring network once again this year. This network is made up of a group of volunteers who set out pheromone traps to help monitor BCW migrations into the state.
BCW does not overwinter in Minnesota - moths move into the state via strong southerly winds, and thunderstorms are often associated with significant moth flights. The larval stage is the damaging stage of BCW. Once larvae reach the 4th instar stage, they are large enough to cut small corn plants. By the third week of May, larvae from early flights this year may be big enough to cause damage to corn. Results and predicted cutting dates can be tracked at z.umn.edu/bcwreporting.
Potter is also leading monitoring efforts for true armyworm. True armyworm is another migratory pest that does not overwinter in Minnesota but is brought up from the south often through storm systems. Armyworm moths are attracted to grassy areas to lay their eggs.
True armyworm larvae feed on grasses including crops such as wheat and corn, but they have been known to feed on soybeans when a grass host is killed. Care should be taken to monitor corn that is planted into ground where a grass cover crop like cereal rye was growing this spring, especially if the cover crop was terminated less than 10 to 14 days prior to corn planting.
Check out these links if you’d like to listen to the podcast of this session at https://strategicfarming. transistor.fm/ or review additional resources at z.umn. edu/strategic-farming.
Join us Wednesday mornings from 8 to 8:30 a.m. through August 21! University of Minnesota’s Strategic Farming: Field Notes webinar series provides useful, timely and relevant research-based information on cropping issues throughout the growing season. For more information and to register, visit z.umn.edu/strategic-farming.
Thanks to the Minnesota Soybean Research and Promotion Council and the Minnesota Corn Research and Promotion Council for their generous support of this program!
