Sept. 15,1925 
Distribution of the Colorado Potato Beetle 
543 
cation than for insect control. Planting dates are later, and hence 
no protection from frost injury is conferred. It is evident, further¬ 
more, that both the ridging and the covering operations under 
western New York conditions are done as the season dictates and are 
not standard cultivation practices. That the covering operation had 
a protective value during the season of 1924 in western New York 
is shown in Table II. 
Table II .—Control effect of the covering operation in western New York 
Operation 
. Not 
covered 
Covered 
Number of varieties__:__ _ 
5 
16 
143 
50.91 
6 
11 
82.9 
13.31 
Number of fields... .._...... 
Acreage__ __ ____ ___ 
Per cent infested____ _ 
INFLUENCE OF THE PREVIOUS CROP 
Examination of field data also indicates that the nature of the 
previous crop has a marked influence on the infestation of the Colo¬ 
rado potato beetle. The usual rotation practice followed in the 
regions studied places sod a year ahead of potatoes, but when pota¬ 
toes precede potatoes in the same soil a very considerable increase 
in the percentage of infestation has been noted. In respect to this 
point, the writer’s figures confirm a relation already observed by 
keen growers. The fact that heavier infestation occurs in fields 
planted the second year to potatoes may be explained by the natural 
sluggishness of the overwintering adults on emergence in the spring. 
Finding the cultivated potato close at hand they accept the plant 
and give rise to the first brood upon it. The origin oi these over¬ 
wintering adults may be traced to two sources. Injured tubers left 
in the field after harvest attract late-emerging adults of the second 
brood Which are obliged to accept them as food in place of foliage 
for a short interval before entering winter hibernation quarters. 
Naturally the presence of overwintering adults in soil previously 
planted to potatoes is also explained by infestation the previous year. 
The importance of this factor of the previous crop in influencing the 
percentage of infestation is shown in a comparison of two adjacent 
fields in which potatoes were growing under identical conditions, 
except that in one the previous crop had been potatoes and the other 
had been in sod (Table III). 
Table III .—The effect of the previous crop 
A.—In Typical and Adjoining Fields 
Field 
No. 
Variety 
Planted 
Fertili¬ 
zer 
Ridging 
Previous 
i crop 
Per cent 
infested 
2291 
2292 
2176 
2177 
Jersey Giants.. 
.do__ 
May 10 
_do_ 
3-8-6 
3- 8-6 
4- 8-4 
4-8-4 
Medium. 
.do.. 
_do_ 
Potatoes. 
Sod__ 
87 
2 
28 
2 
Tfiph Cohblp.r _ 
_do_ 
Potatoes. 
_do_ _ _ _ __ 
May 5 
_do_ 
Sod__ 
