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 European Corn Borer Summer Moth Flights Have Peaked, Prepare for 2nd Generation Minimize
Location: BlogsWisconsin Crop ManagerInsects and Mites    
Posted by: WCM Staff 8/4/2005 11:43 AM
For those who may not have caught last week’s (July 29) issue of the WI DATCP Wisconsin Pest Bulletin, please be aware that emergence of the summer flight of European corn borer moths has peaked in parts of Wisconsin.

European Corn Borer Summer Moth Flights Have Peaked, Prepare for 2nd Generation

 

Eileen Cullen, Extension Entomologist UW Entomology Department

 
For those who may not have caught last week’s (July 29) issue of the WI DATCP Wisconsin Pest Bulletin, please be aware that emergence of the summer flight of European corn borer moths has peaked in parts of Wisconsin. This knowledge is made available by the work of Krista Lambrecht and the Wisconsin Pest Bulletin survey team. Rather than reinvent the wheel, I have inserted Krista’s bulletin within this Wisconsin Crop Manager edition. You can access the article and the entire July 29 issue of the Wisconsin Pest Bulletin at http://pestbulletin.wi.gov/ .
 
Second generation European corn borer egg laying occurs over a long period of time and infestations can go unnoticed until ears begin to drop and stalks begin to break in the fall. Due to the extended egg-laying period, one sampling of a field is not sufficient. Scout fields weekly after peak moth flight, looking for white egg masses on the undersides of leaves near the midrib. Most of the 2nd generation eggs will be laid on leaves near the ear and above. Use the UW Extension management worksheet below to determine whether treatment will be worthwhile.
 
EUROPEAN CORN BORER – (Source: Krista Lambrecht, WI DATCP, WisconsinPest Bulletin).
 
Emergence of the summer flight of corn borer moths has peaked near Beloit, Lone Rock, Madison, Sullivan and LaCrosse, where 1733 GDD50 have been reached. First instar larvae can be found in south central, southwest and west central cornfields. The treatment window for second generation corn borer larvae remains open for another 17-19 days in these districts, or until 2100 GDD50 have accumulated.
 
On average, the impact of second generation corn borer is expected to be light to moderate; however, hotspots are certain to emerge. Surveys of first generation borers in mid-June found localized heavy populations in the central and south central districts, particularly in southern Juneau, Monroe and Dane Cos. (near Stoughton), but no there was no discernable pattern to the location of hotspots. Remarkably high black light trap captures in the past two weeks near Plover in Portage Co. (329 moths) indicate some heavy infestations of second generation borer can be expected in that area as well. Now is an ideal time to assess numbers of egg masses and stalks infested with second generation borers to determine the need for control. Treatments in field corn should be applied at hatch and may be necessitated when 50% of the plants are infested with eggs or small larvae.
 
Black light trap captures from the period of July 22-28 are as follows: Plover 329; Plainfield 10; Janesville 42; Lancaster 4; West Arlington 54; Stoughton 3; Chippewa Falls 6; Marshfield 0; West Madison 39; Mazomanie 27.
 

 
The Management worksheet for Second-Generation European Corn Borer (above), as well as insecticides  labeled for European Corn Borer control are available in UWEX Publication A3646 Pest Management in
 

 
If possible, treat when tiny black dots are apparent on most of the egg masses. At this “black head” stage, the eggs arealmost ready to hatch.  (See image above.)

 
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