8 BULLETIN 892, U. S. DEPARTMENT OF AGRICULTURE. 
far the greatest number of larve usually develop on it. Large areas 
of this plant, acres in extent, are often killed by the insects. The 
dead plants turn black and, at a distance, appear as though injured 
by fire. The spikelike leaves of young Russian thistle are eaten by 
the larvee but are not a favorite food. While large numbers of larve 
frequently develop on sugar beet, this happens as a general rule only 
in the event of a scarcity of the favorite natural food plants. Larve 
are sometimes so abundant on sea-blite and lamb’s-quarters about 
the margins of beet fields that the plants are killed (Pl. VI, C, D) 
and become dry, causing the partly-grown larve to crawl into the 
beet fields and complete their development on the beets. 
Eggs are occasionally deposited on sea purslane and on some 
other weeds, but the larvee have not been observed developing on 
these plants. | a 
OCCURRENCE AND EXTENT OF INJURY. 
The beet leaf-beetle, under natural conditions, lives upon weeds 
growing on land which, in many cases, is too highly charged with 
alkali to support cultivated crops. This waste land occurs through- 
out the upper Arkansas Valley in Colorado in low portions where 
excessive quantities of alkali have accumulated through natural 
drainage or by seepage from the irrigation ditches. These alkali 
areas vary in extent from a few square rods to many acres. Some 
of the alkali land has been partially or wholly reclaimed by tile 
drainage and, in many cases, the worst alkali spots adjoin or are 
surrounded by highly cultivated land. (See Pls. IV, V.) 
Sugar beets and sorghum, being particularly resistant to alkah, 
are frequently grown on land which is too “salty” to produce 
profitable crops of less resistant plants. Sorghum is not injured but 
the foliage of sugar beet is well liked by the beetles, and when this 
crop 1s grown on or near the alkali areas it is frequently severely 
damaged. 
As long as there is a supply of the natural food plants available 
little damage is done to sugar beets. In the spring, before the 
weeds become abundant, the overwintered beetles, and more rarely 
the larvee, may infest small, young beets and completely destroy them. 
Later the insects may develop in such enormous numbers that many 
of the weeds are killed and they may then resort to sugar beets for 
food. Many hundreds of acres of beets are infested every year. 
(See Pl. IL.) 
The injury resulting from infestation varies greatly, depending 
upon the abundance of the insects and the size of the infested beets. 
Small beets may be completely destroyed, while larger plants may be 
partially or completely defoliated and checked in growth. (See PI. 
VI, A, B; Pls. VII-IX.) Usually the acreage that is destroyed is 
ep 
