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Return to NW Iowa Crops Homepage
1st Generation Bean Leaf Beetle
Begin scouting for first generation Bean Leaf Beetles next week in the earliest planted soybeans. Peak 1st generation emergence will occur around 1212 GDD’s following soybean emergence. ISU has developed a new control strategy (for 2nd generation beetles in Mid-August and September) based on 1st generation population numbers. Based upon a high density of first generation beetles, it is expected that the second generation will exceed the economic threshold. This new management concept stops the second-generation beetles long before they reach the old economic threshold.
Degree Day Accumulation for emergence of 1st Generation BLB based on emergence date of the soybean field.
The first thing to do is determine the week soybeans emerged, then refer to the accumulated GDD table and match dates. Begin sampling fields 1 week after peak emergence. If the sample is below threshold, scout again the next week. If the sample is still below threshold, scout 1 more week. If 1st generation beetles are above threshold, scout again mid August to confirm beetles are present, then spray.
Notice: This is scouting of 1st generation beetles to determine control of 2nd generation beetles.
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Table 2. 1st generation economic thresholds necessary to spray 2nd generation beetles |
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treatment cost per acre (insecticide + application) |
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crop value ($/bushel) |
$10.00 |
$12.00 |
$14.00 |
$10.00 |
$12.00 |
$14.00 |
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beetles per 3 row feet |
beetles per 20 sweeps |
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$5.00 |
7.9 |
9.5 |
11.0 |
32.6 |
39.0 |
45.4 |
Return to NW Iowa Crops Homepage
Todd Vagts
Iowa State University Extension
Field Crops Specialist
1240 D. Heires Avenue
Carroll, IA 51401
Office: 712-792-2364; Cell: 712-249-6025; Fax: 712-792-2366
Email: vagts@iastate.edu
For questions or comments please respond to vagts@iastate.edu
This page last updated on 07/21/03
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