INSECT PEST SURVEY BULLS 
LIBRARY 
PLANT board 
Vol, 19 
Summary for 1939 
Supplement 
to No. 10 
1 EUROPEAN CORN BORER 
The seasonal occurrence of the European corn Borer in 1939 was 
about average over the range of its distribution in the United States, a 
partial second generation developing in the Lake States, two generations 
in New England, a small partial third generation in New Jersey, and three 
generations on the Eastern Shore of Virginia. Eirst oviposition records 
for selected localities were as follows: Toledo, Ohio, June 6; Waltham, 
Lass., June 5? New Haven, Conn., May 29; Moores town, N. J. , May 25; 
Onley, Va. , May 10. 
In addition to the previous known distribution of the insect obser- 
vations principally by State personnel provided records of corn borer 
occurrence in 1939 in the following counties: Lodge, Green Lake, Jefferson, 
tconto, Outagamie, Shawano, end Waupaca in Wisconsin; Cook, Du Page, 
Kankakee, Lake, and Will in Illinois; Chester, Lelaware, Lancaster, and 
Montgomery in Pennsylvania; Kent and New Castle in Delaware; Lancaster, 
Nansemond, and Richmond in Virginia; and Camden, Currituck, and Pasquotank 
in North Carolina. The Illinois and North Carolina infestations are the 
first records of occurrence of the corn borer in these States. 
The greater portion of the known area of corn borer infestation was 
included in the annual fall survey of abundance in 1939. conducted by the 
Bureau in cooperation with various interested States, although comparisons 
of populations between 1933 and 1939 nre restricted to districts also 
surveyed in the former year. In these districts, a general increase 
occurred in Indiana, while marked decreases occurred in Connecticut and 
New Jersey. In Connecticut, however, first-generation oviposition and 
infestation were particularly heavy, the factors contributing to the decrease 
in the fall population having been expressed after the completion of the 
first generation. The remaining districts for which comparable data are 
available carried similar populations for the 2 years, minor increases 
and decreases appearing scattered over the territory. Except for critical 
areas in eastern Michigan, £n Ohio extending southwest of Lake Erie, and 
in the Eastern States extending from Massachusetts to New Jersey, borer 
populations in general averaged less than 100 borers per 100 plants. 
The greatest abundance was found in southern Now England, where 5 counties 
* in eastern Massachusetts, 2 in central and 2 in eastern Connecticut, and 
4 in Rhode Island averaged over 500 borers per 100 plants, and in the tip 
of the "thumb" section of Michigan, where 1 county had a population of 
595 borers per 100 plants. Selected fields in New Jersey continued to 
carry heavy borer concentrations with averages of l6 to 40 borers per plant. 
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