THE BEET LEAF-BEETLE. 9 
small, although in some years, in 1909 for example, 200 acres of sugar 
beets in the Arkansas Valley were observed that were literally 
“wiped out.” As a rule, the most noticeable loss resulting from 
infestation is a reduction in sugar content which follows defoliation. 
Owing to various other factors which tend to increase or decrease the 
sugar in the beets, it is impossible to state definitely how much loss 
may be expected from defoliation by the beet leaf-beetle. Compara- 
tive analyses have indicated, however, that injury varying from par- 
tial to complete defoliation during August may result in a loss of | 
from 5 to 25 per cent of sugar. 
During the summer of 1912 Miss V. W. Pool, of the Bureau of 
Plant Industry, discovered that the beet leaf- Beetle may serve as an 
agent in distributing the spores of the leaf-spot disease (Cercospora 
beticola Sace.). July 31 Miss Pool collected four beetles from sugar 
beets at Rocky Ford and confined them for a few minutes in a cul- 
ture plate of bean media. One colony of Cercospora developed in 
this plate. 
In feeding on sugar beets the beetles cut large irregular holes 
(Pl. VIII; Pl. TX, A) through the leaves. The older, outer leaves 
are preferred, and when riddled the portions between the holes turn 
brown and fall away, leaving nothing except the petioles and larger 
veins. As previously mentioned, the insects prefer certain weeds 
as food, and as a rule spread to the beets when the favorite weeds 
are scarce or exhausted. As a result the beets growing nearest the 
weeds are the first to become infested. 
The beetles are strong fliers, and during July and August may 
spread pretty generally over beets growing near alkali areas. <A 
field of beets may be generally infested, but almost invariably there 
will be certain areas, varying from 6 to 20 or more feet in diameter, 
where the beetles congregate in large numbers. As many as 200 or 
300 beetles may occur on single large beets, and the foliage is natur- 
ally more quickly destroyed than on less badly infested plants. As 
a result these areas are usually conspicuous in infested fields. 
The larve feed in exposed positions on the upper or lower sides 
of the leaves. On thick-leaved plants they may eat pits in the leaves 
without cutting through, but on thin-leaved plants they usually cut 
irregular holes entirely through the leaves. 
When mature the larve leave the plants and burrew into the soil 
to a depth of a half inch to 2 inches and form cells by wriggling 
about. The soft, yellow pupe are formed in these cells. The adults 
develop in the cells and usually remain in them for two or three 
~days. When they emerge they are dull yellow and soft. They com- 
mence to feed at once and become hardened and attain full color 
within a few days. 
186598 °—20——2 
