456 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
show the man who produces that we are as good business men as he, 
that we understand his problems, and that we can help him make 
more money. 
Chairman A. L. Melander: At this time I shall present a paper 
entitled: “ An Index Number for Rating Codling Moth Treatments.” 
AN INDEX NUMBER FOR RATING CODLING MOTH 
TREATMENTS 
By A. L. Melander, Pullman, Wash. 
Fruit growers and entomologists have long felt the need of more 
exact methods of comparing the results of spraying than laboriously 
to sort over thousands of apples at harvest time and announce results 
in percentage of worminess. To gain accuracy it has been the custom 
to give a uniform treatment to a block of many trees and then to obtain 
counts from the central trees of the block. Even so, the central trees 
do not always produce the same percentage of worminess, for no matter 
how large a tract is treated individual trees will vary in the codling 
moth population they support. When it comes to comparing the 
value of different brands of similar sprays all used stronger than the 
minimum lethal dosage, when comparisons are to be made of differing 
methods of applications, when comparisons are to be made under 
conditions of varying infestation, or with trees of various ages, or in 
widely separated localities, the method of mass spraying and subse¬ 
quent examination of selected trees for worminess has proved labori¬ 
ous, costly, inadequate, crude, and even misleading. 
The western fruit grower is much concerned with “stings” on his 
fruit,—not the curculio stings of the East, but the spots resulting 
from the nibblings of those codling worms that died on their way into 
the apple. Wormy apples are not to be sold, but under certain 
restrictions stung apples can go on the market as lower grade fruit. 
In as much as a wormy apple shows that the codling moth spray was 
in that instance ineffective, but a sting usually indicates that the spray 
accomplished its purpose, we have in the ratio of worms to stings a 
simple and ready index to judge the merits of the particular treatment. 
Relatively the more stings there are the better the treatment has proved. 
It is much easier to express and compare treatments in terms of such 
index numbers than to keep in mind a series of variable factors, like 
the previous history and present contamination of the trees, when 
interpreting results. 
