352 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
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use of supplementary control measures. It is therefore evident that 
the codling moth, instead of being a more or less fixed quantity, and 
subject to reduction in numbers, as control methods have been im- 
proved, has undergone an adaptation or evolution that has permitted 
the insect to hold its own or even to increase in numbers in spite of 
man’s efforts. 
CHANGES IN CONDITIONS 
First, the standards by which control is judged have been modified 
from time to time. With the trend toward the concentration of com- 
mercial apple production in areas remote from markets, only high- 
grade fruit is worth the cost of shipping thousands of miles, and in 
such areas moderately injured fruit, which in localities near the con- 
suming centers might bring fair prices in local markets, is now a total 
loss. Also, the American public demands a higher standard of per- 
fection in its fruit products than ever before. This all means that our 
standard of satisfactory control is much higher than it was 50 
years ago. 
Many of the practices adopted by fruit growers have given advan- 
tages to the codling moth. Apple production has passed from small, 
isolated farm orchards to more intensive production in limited areas. 
In these newer areas conditions are sometimes especially favorable for 
the apple crop, but in other cases there has been extensive promotion 
of apple culture outside the range within which the apple would nor- 
mally thrive. In either case, this trend has been an important factor 
in favor of the worms. With an abundance of its favored food avail- 
able in virtually continuous, extensive acreage, with improved varieties 
and cultural methods that have to a certain extent eliminated the 
biennial bearing habit that characterized many of the older apple vari- 
eties, a factor that automatically held the codling moth population at 
a low point, it is not surprising that the present-day grower has to 
deal with a more numerous population. As these areas have come into 
full bearing, the mature trees have often reached such size that spray 
coverage has been poor. 
The benefits derived from the extensive use of insecticides have un- 
doubtedly been offset to some extent by their unfavorable effect on the 
abundance and activities of parasites and predators of the codling moth. 
Evidence has been obtained in New York State (Cox, 1932; Collins, 
1934) that one of the most important larval parasites of the codling 
moth, namely Ascogaster quadridentatus Wesm., is adversely affected 
by lead arsenate and that in sprayed orchards the percentage of para- 
sitization is less than half of that existing in unsprayed orchards. It is 
not at all improbable that the effectiveness of other parasites and per- 
haps predators is also very much reduced by the continued use of lead 
arsenate. This factor may have been an important one in permitting 
