Tips to Access Rootworm Activity
Earlier this summer Latham Corn Product Specialist Nick Benson posted a blog, reminding farmers to scout every field for rootworm. Because of the wide variance in planting dates in 2013, it’s important to continually inspect every field.
With adult corn rootworm becoming active during silking this year, we highly recommend keeping an eye on fields in order to protect yield. Now it is a good time to assess corn rootworm activity: score injury caused by larvae, and monitor adult activity in corn.
Late-planted fields or late-flowering hybrids are generally attractive to adult corn rootworm beetles. Silks will still be developing in these fields when older fields have brown or drying silks, so adults may migrate and aggregate in this later-maturing fields.
Also evaluate root injury to better understand the efficacy of your management program. Monitoring over several years will help establish a historical record of how larvae respond to management tactics (e.g., crop rotation, Bt corn, soil insecticides, etc.). One common outcome of severe larval feeding is lodging of corn plants. However, it is important to confirm that feeding from corn rootworm was the cause of lodging and that it did not results from other factors such as strong winds.
To help assess injury, ISU Entomologist Aaron J. Gassmann developed an Interactive Node Injury Scale. Injury assessment made now and field notes taken will help you select seed products for 2014. To prevent corn rootworm damage from reaching devastating levels, plant a portfolio of products.
Continued use of the same rootworm-resistant trait in corn hybrids, an increase of corn-on-corn areas, plus a lack of refuge acres, has caused rootworm resistance to become an issue in some areas. Best management practices to reduce corn rootworm pressure in the future include: crop rotation, trait rotation and respecting the refuge.