Meeting will be at the Willkommen Park Pavilion ( 21 Main St . East , Norwood Young America ) Friday , Dec . 15 , 2023 Lunch at 12 noon • 1:00 pm Meeting For more information , call our office - ( 952 ) 466-3700
AGRONOMY
Managing the surge in corn rootworms : critical tips and recommendations for the 2024 growing season
Ryan Pawelk Sales Agronomist
( 952 ) 466-3730
We need to keep corn rootworm management at the top of our priority list in 2024 . Low frost depth in the winter and less rain in the spring at the time of egg hatch have allowed rootworm populations to explode . This has led to significant root and silk feeding damage in the corn again this year . The worst of it was contained to corn-on-corn fields , but some damage was also seen in adjacent fields that were rotated . Even with corn rootworm traits , there was lodging . This does not mean the traits failed . We need to remember that for the traits to work and kill the rootworm larvae , they need to bite into the root and ingest the proteins . However , when larvae populations are very high , so are the number of bites on the roots , thus leading to roots being chewed off , root rot diseases and eventually root lodging .
After root feeding , the ones that survived emerged as beetles and started feeding on the silks . Males emerged first and then females about a week later . Because some corn was planted late this year , the silks were not out yet when the beetles emerged . So , they either hung out on the
corn leaves waiting for the silks or they flew into adjacent corn fields that already had silks out . The pictures show silks clipped off and the resulting tipback in a field that was soybeans in 2022 . This field was across the road from a neighboring continuous corn field .
Many beetles were also found in adjacent soybean and alfalfa fields looking for a food source . Late August I observed adult rootworm beetles feeding on alfalfa leaves causing noticeable damage . In the inserted picture , the northern corn rootworm beetles are circled in red and are seen feeding on the alfalfa leaves . What ’ s concerning with this is that it ’ s very possible that the females laid eggs in these fields which now can be a problem if they are rotated to corn this coming year .
So here are some tips to help manage corn rootworms .
• Avoid planting corn-on-corn . Crop rotation is key to rootworm management .
• Know your neighbors crop rotation and practices . If they are planting corn-on-corn next to your fields , it will be important to scout and monitor rootworm populations in your field .
• If rotation is not an option , continue using rootworm traited corn . Use varieties that have multiple rootworm trait modes , know what proteins you have , and rotate them the following year . For example , if you used a SmartStax variety last year ,
rotate to a variety that has Duracade this year , or vice versa .
• Its highly recommended to use an in-furrow insecticide at full rate in addition to using traited corn . The insecticide will help reduce the initial population and take pressure off of the seed traits .
• Take out volunteer corn which attracts beetles to move into soybean fields and lay eggs for the next year when its rotated back to corn . Another key point is that volunteer corn does not express the full amount of the rootworm traits . This allows rootworms to survive and develop resistance to the traits .
• Scout for emerging beetles at tassel to prevent silk feeding . Putting out sticky traps can help with this which we can provide you . If populations are high and silk feeding is expected , apply a foliar insecticide at full rate . Remember that the males emerge first and the females a week later . So scouting needs to be done a week after application . If female beetles are high and pollination is still ongoing , a second application will be needed .
• Scout for female beetles late summer and early fall . These are the ones that will lay eggs in the soil for the following year .
Contact us to further discuss how we can help you make the best decisions in managing corn rootworms .
NOTICE Mid-County Coop Annual Meeting
Meeting will be at the Willkommen Park Pavilion ( 21 Main St . East , Norwood Young America ) Friday , Dec . 15 , 2023 Lunch at 12 noon • 1:00 pm Meeting For more information , call our office - ( 952 ) 466-3700
www . midcountycoop . com