•U30- 
LAKE STATES (MICHIGAN, INDIANA, OHIO, 
■':iA, J ' ' ;k) 
Definite decreases in infostcti.cn in 193^. a " compared with 1935> 
occurred in eastern Indiana, where one average n imber borers ] r 100 
plants decreased iron 9-3 in 1935 to 3-2 'in 193 ■; — the lower two-thirds 
of the region surveyed in the western half of Ohio, "here the average number 
of borers per 100 plants diminished from 22. 5 in 1935 to 3-5 in 193^5 ?*nd in 
the "thumb" section of Michigan, whore the average qui r oi rrrs pi r 100 
plants decreased from 1^2. 7 in 1935 to 55*3 i n 193^* ^- s a result f oh 
decreases in population, the status of the corn borer in the al y e portions 
of the infested territory in 193 ^ was little changed from that prevalent in 
the drought year of 193^. with a ractical elitoin; L a of the gain in 1935* 
These decreases in numbers of the borer in 193'' ' " attributed to drought, 
particularly to the effect of a lac': of rainfall in the first half of July, 
supplemented by abnormally high temperatures lent during the second week 
of that period. 
Borer populations in the nortl: restorn corner of Ohio and the south- 
eastern part of Michigan, west cf Lake Erie, however, were at least as 
high in 193- as in 1935? with significant ir creases aj ; in 11 of the 
23 counties surveyed and with tea.'. ; :ies to increase of the 
remaining counties. In general, the: • a more favorable moisture distri- 
bution in these s 'ctions than in the areas that sh i Lfestation. 
This permitted multiplic; borer despite an a; 'ecicble reduction 
of live forms early in the season, owing to a pupal mora Lty roxi- 
mately 20 percent caused by excessive heat t. s ;ond week of J . ■'. r- 
theless, the high temperatures detrimental to the pup* *e probably res- 
ponsible for the product ion of a limited socond generation of the corn borer 
in this area, the progeny fr ra which augmented, in some cases, the fall 
population figures. However, both in the survey.:-! part of Ohio, as a whole, 
and in southeastern Michigan, including the regions of decrep.se in both 
States previously mentioned, there was a significant increase in the average 
number of borers per 100 plants in 193 ' ' 1935- I n Ohio, this aver? 
increase was from J>$.% borers per 100 plants in 1935 to 5O.6 in 193^. and 
in Michigan, from U5 . 7 borers per iants in 1935 to 57 • S in 193^. 
Corn borer infestation in the Like States in 193^ was most intense 
west and south of the w t end of lake Erie, and the highest populations, 
observed as in 1935. were in Lucas and Wood Z . Ohio, with averages 
of lbl.5 and 138. U borers per 100 planes, rest jctively. (or U5 
percent) of the ho fields surveyed in the two counties had populations 
ranging from 115 to 727 be rs per 100 plants. 
The borer was found to be present in negligible numbers in central 
Indiana and In the southwest srn corner of en, over a region not sur- 
veyed in the past 3 years. It is probable tl I drought prevalent in 193^ 
also operated in this territory to reduce infi Lon. 
In parts of central :. not previously surveyed, the borer was 
found to be practically as abundant as in some of the older infested countios 
of the eastern section of the State. An •■• rv infestation of 68.5 borers 
