78 
SPRAYING APPLES FOR THE PLUM-CURCULIO. 
It has been known for more than a hundred years that the 
apple was sul^ject to injury by the pluni-curculio, but as this injury 
has been commonly reckoned less important than that done by the 
codling--moth, the matter has received, of late, comparatively little 
attention until within the last six or seven years. Since the dis- 
crimination of different market grades of apples has been generally 
introduced — a grading based not only upon size and soundness, but 
also upon superficial ■ appearance — the slight surface injuries done 
by the new generation of the plum-curculio, both in laying the eggs 
and in feeding on the fruit, have acquired a great importance. The 
consequence of a noticeable injury of this sort, although affecting 
but little, and in many cases scarcely at all, the edible quality of 
the apple so injured, is to reduce its selling value from No. i grade 
to No. 2, the actual profits of the crop disappearing in this process. 
These facts having been repeatedly brought to my knowledge by 
Illinois horticulturists, I undertook to work out the causes of these 
surface blemishes in general, and to demonstrate more accurately 
than has hitherto been done means of preventing them by a destruc- 
tion of the curculios themselves. Indeed, the importance of this 
investigation has grown upon me as it has become evident that 
these small superficial injuries very often give entrance through the 
skin of the apple to bacteria and to fungus spores of various kinds, 
causing rots and blights of the fruit which might be largely pre- 
vented by a timely destruction of the insects. 
Some Earlier Experiments. 
The first exact experiments with insecticides for the protection 
of apples against the plum-curculio were those made at my office in 
1885, on a small orchard hired for the purpose near Urbana, 111., 
the results of which were published in one of my reports*, and in 
the Transactions of the Illinois State Horticultural Society for that 
year. In this experiment, which was made primarily to test insecti- 
cide measures for the destruction of the codling-moth, the effect on 
*Misc. Essays on Econom. Ent., 1886, pp. 26-45. 
