2018
Extension and research to combat insecticide resistant soybean aphids
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Contributor/Checkoff:
Iowa Soybean Association
Category:
Sustainable Production
Keywords:
Biotic stressCrop protectionField management Pest
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Erin Hodgson, Iowa State University
Co-Principal Investigators:
Project Code:
Contributing Organization (Checkoff):
Iowa Soybean Association
$92,699
Institution Funded:
Iowa State University
$92,699
Brief Project Summary:

Growing evidence indicates that soybean aphid is developing field-evolved resistance to pyrethroid insecticides. Pyrethroids are popular for soybean aphid management because they have excellent efficacy and are inexpensive. However, pyrethroid-resistant aphids will complicate management practices and farmers could expect a yield loss of 25-40% when using ineffective tools. This research addresses challenges for managing soybean aphids considering pyrethroid resistance by identifying the geographic range of pyrethroid-resistant soybean aphids in Iowa and learning to limit the spread of resistant populations with appropriate tools. Work aims to map pyrethroid resistance, understand the mechanism of resistance in soybean aphid, develop a diagnostic tool and provide recommendations to protect yield and minimize input cost.

Key Benefactors:
farmers, agronomists, Extension agents

Information And Results
Project Deliverables

• Raise awareness of pyrethroid resistance among farmers and ag industry [short term knowledge];
• Implement scouting and adopt economic thresholds for soybean pests [long term skill];
• Recognize options for managing soybean aphid, including alternative insecticides, host plant resistance, etc. [long term knowledge];
• Reduce insecticide use, including seed and foliar treatments [long term skill];
• Understand the implications of soybean aphid genetic resistance to insecticides [long term knowledge]; and
• Improve profit margins by reducing input costs [long term knowledge].

Final Project Results

Update:
Soybean aphid populations throughout Iowa were lower than in 2017. As a result, few commercial fields were sprayed and we did not respond to any “performance failures” this summer. The lack of reports does not mean pyrethroid-resistant aphids were absent in Iowa.

Dose response analyses were performed to evaluate the susceptibility of soybean aphid populations to lambda-cyhalothrin, an insecticide used to control aphids in soybean. Three laboratory populations (Biotypes 1, 3, 4) and three field populations (Sutherland, Minnesota colonies 1 and 2) collected in the Summer of 2017 were screened using leaf dip bioassay as recommended by the Insecticide Resistance Action Committee (IRAC), and LC50 and resistance ratios were calculated. Results indicate no variation in the susceptibility between biotypes 1 and 3; however, the LC50 of biotype 4 was almost twice as the LC50 of Biotypes 1 and 3. Field-collected populations also demonstrated different susceptibility to lambda-cyhalothrin when compared to the Biotype 1 colony (hereafter as susceptible colony). The population from Sutherland, IA, had a resistance ratio of 3.7. The two Minnesota colonies had similar LC50s and resistance ratios of 45.8 and 36.65, respectively.

View uploaded report Word file

Exceptional progress was made in 2018 regarding developing a protocol to evaluate pyrethroid resistance for soybean aphid. We are using a combination of lab and growth chambers experiments on several lab colonies. In addition, we are preparing to use molecular genetic techniques to describe how insecticide resistance is developing for soybean aphid.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.