Integrated Crop Management News Extension and Experiment Station Publications 7-23-2019
Assessing Corn Rootworm Activity UsingSticky Traps
Assessing Corn Rootworm Activity UsingSticky Traps
Ashley Dean
Iowa State University, [email protected]
Erin W. Hodgson
Iowa State University, [email protected]
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Recommended Citation
Dean, Ashley and Hodgson, Erin W., "Assessing Corn Rootworm Activity UsingSticky Traps" (2019). Integrated Crop Management News. 2576.
https://lib.dr.iastate.edu/cropnews/2576
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western corn rootwormresistance to all Bt rootworm traits in Iowa.
Disciplines Disciplines
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Integrated Crop Management
Assessing Corn Rootworm Activity Using
Sticky Traps
July 23, 2019
Western and northern corn rootworm are major corn pests in Iowa and surrounding states (Photos 1 and 2). Farmers have seen several management changes, including the release of four Bt-rootworm traits to suppress corn rootworm larvae since 2003. Although both species are persistent pests, western corn rootworm is particularly adaptable. The Gassmann Lab at Iowa State University (ISU) has confirmed western corn rootworm resistance to all Bt rootworm traits in Iowa.
Photo 1. Color and size variation of western corn rootworm. Photo by Adam Varenhorst.
make management decisions based on larval injury to roots or adult activity. We
recommend using the 0 to 3 node-injury scale developed at ISU to evaluate larval injury. Corn rootworm egg hatch peaked mid-June this year, and adults are beginning to emerge in many fields.
Adult emergence coincided with silking in corn this year throughout much of Iowa. This can be problematic as adults can clip silks and interfere with pollination. To monitor for adults, follow the guidelines outlined below. Use Pherocon AM yellow sticky traps
(unbaited). Set up sticky traps at corn silking and continue through the dent stage (i.e., mid-July through August). For areas in eastern counties with suspected rotation-resistant western corn rootworm, set up sticky traps at soybean flowering and continue through full seed set (i.e., mid-July through August).
Guidelines for sampling adult corn rootworm
1. For every 10-50 acres of corn or soybean, create two transects of six sticky
traps/transect (Figure 1). Transects should be at least 330 feet apart. Use a flag or stake to mark transects along the field edge.
2. Place the first trap at least 165 feet in from the field edge; place remaining traps within the same row and at least 165 feet apart.
3. For corn, attach the sticky trap directly to the developing ear. For soybean, attach the sticky trap to a post approximately 18 inches above the canopy.
4. Check traps weekly and count the number of western and northern corn rootworms. Replace sticky traps weekly and adjust trap height if needed.
5. For each sample, estimate the average number of western and northern corn
rootworms per trap per day. For example, 123 total corn rootworms/12 traps/7 days = 1.46 rootworms/trap/day.
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Figure 1. Schematic drawing of adult corn rootworm sticky traps in corn or soybean fields.
Category: Crop Production Insects and Mites
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Crop:
Corn
Tags: insect sampling rootworm sticky cards
responsibilities in corn and soybeans. She has a general background in integrated pest management (IPM) for field crops. Dr. Hodgson's curre...
