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Abundance in Sweet --Corn and White Potatoes 
Special surveys of abundance of the first generation of' the European com 
borer in early market sweet corn and in white potatoes were conducted in several 
localities in the summer of • 1^3 9 ^ In the case of sweet corn the surveyed field 
represented those most heavily infested within a given locality. Fields of 
potatoes were surveyed at random. -> ; The data on sweet corn are given in table 3* 
* . | 
Infestation of the European copn borer in early market sweet com in 1939 
was most severe in New Heaven County, ,-Gonn. , where half of the fields surveyed 
averaged 20 or more borers per 100 plants, and in Ulster County, N. Y,, where 
the same proportion of fields averaged 10 or more borers per .100 plants. In Now 
Haven Countv the .average number of borers per 100 plants was 1,980 and in Ulster 
County 1,264. The greatest increase of the pest in sweet corn occurred in Bur- 
lington County, N. J. , where an average of 50 borers per 100 plants in 1938 
changed to 4l7 in 1939* Less than half as many borers infested the crop in Lucas 
County, Ohio, in 1939 » when the average number per 100 plants was 817, as in 1938 
when it was 1,75Q» The heaviest population in early market sweet corn in any 
of the 4 counties surveyed in southwestern Maine in 1939 was in York County where 
there were 125 borers per 100 plants. 
The corn borer was less abundant in 1939 than in 1938 in white potatoes 
grown in central Connecticut and Massachusetts, In the former State the number 
of borers per 100 potato plants in 1938 was 358 , as compared with l45 in 1939 ; 
in the latter State, the population of the insect in each. 100 plants was 280 in 
1938 and 17 O in 1939* The number of borers per 100 plants of potatoes in central 
New Jersey in 1939 averaged 17.9* " ‘ ‘ 
There is little doubt that the relative status of the European corn borer 
in 1939 / as in other years, was influenced to a great extent by prevailing 
weather conditions during certain critical stages of the insect’s development 
but it is difficult to give exact and satisfying reasons for the increases, de— 
creases, or comparative stability of populations of the pest in the comparable 
territory surveyed in 1938 and in 1939« Dryness in the spring or summer months 
was probably the most adverse factor influencing survival of the corn borer in 
1939, although too abundant rainfall at particular times may also have been un^ 
favorable to the insect. Extremes in moisture conditions characterized the 
summer of 1939 in practically all sections of the country concerned in this re- 
port, whereas fluctuations in temperature were in general ‘less pronounced. For 
instance, April was the fourth consecutive wet month in New Jersey and was also 
wet farther south along- the Atlantic coast. The month of May was generally dry 
from Indiana east to the New 'England coast and south through New Jersey to the 
Eastern Shore of Virginia. In June precipitation was excessive in Ohio, Michigan, 
and Indiana but in the more eastern States it varied slightly above or below nor- 
mal, While moisture conditions in July were about normal in Ohio, Michigan, and 
Indiana, the weather that month in New York State and east through most of New 
ng land and New Jersey developed int^ a serious drought* In New York dry weather 
continued into August and in Ohio the month was one of the driest A-ugusts on 
record. On the other hand August was a month of excessive rainfall in New Jersey 
and New England. 
2 / 
The survey of sweet com in New York was made in cooperation with the AgricufturrJ 
Experiment Station, Geneva, N. Y, , and the data on infestation in this crop in 
Maine were kindly furnished by the State Department of Agriculture of Maine, 
