SCIENCE AND INDUSTRY. 
Insect Enemies. 
A CALIFORNIAN EXPERIENCE. 
Insects introduced 5 Combating Beet Leaf 
from Australia. _ Hopper. 
By E. J. VOSLER.* 
Before going into an account of the writer’s trips to Australia, which were 
made primarily for the purpose of securing enemies of the beet leafhopper, 
Eutettix tenella, Baker, it might be of interest to give a brief summary of 
the work of this insect in California and elsewhere, and the reasons for under- 
taking this investigation. 
For some years it has been known to entomologists that the leafhopper, 
Eutettix tenella, has been associated with the disease known as curly-leaf, 
which is destructive to the culture of the sugar beet. In 1909 the United 
States Bureau of Entomology published a bulletin, by E. D. Ball, on the 
leafhoppers of the sugar beet, in which a detailed account was given of the 
curly-leaf disease in the inter-mountain States, and the role Eutettix tenella 
plays in the transmission. Ball states in this bulletin that as early as 1897 
the sugar beet crop around Lehi, Utah, suffered a serious loss. It was not until 
1905, however, that it was noticed, in fields where curly-leaf was prevalent, 
that large numbers of the beet leafhopper were present, and it was first 
suspected that this leafhopper might in some way be connected with the 
diseased condition of the sugar beets. The study of this disease was begun 
by Ball in 1905, and continued in 1906 and 1907. The results of his work . 
show that the curly-leaf condition of the beets appears soon after the leaf- 
hoppers are found in the fields, that the severity of the disease is contingent upon 
the numbers of this species present, upon the time of their appearance and 
upon climatic conditions. Investigations continued by Ball, Stahl, Smith and 
Boncquet have definitely proved that the bite of this particular leafhopper is 
necessary for the transmission of the curly-leaf disease to healthy beets. Just 
what the casual organism of curly-leaf is has not been determined. Recently ~ 
Stahl and Carsner have published the information that leafhoppers which have 
never fed on beets affected by curly-top will not produce the disease on healthy 
beets. Sufficient proof has thus been obtained, pointing to Eutettix tenella as 
the guilty party in the inoculation of sugar beets with curly-leaf. 
In beet leaves first affected with curly-leaf there is a thickening of the 
_ Smaller veins, the undersides presenting a roughened appearance. ‘The edge 
of the leaf curls up and finally the whole leaf curls. As the disease advances 
the smaller veinlets grow still larger, and irregular, knot-like Swellings become 
noticeable. In some cases the beets shrivel and die, in others they partially 
recover and a new set of leaves develops. The sugar content remains low in all 
affected beets,,and consequently the logs is greater than usually is supposed. 
ne . = i . 
The full-grown leafhopper is a small, pale yellowish-green insect about an 
eighth of an inch in length. The eggs are elongate, slightly curved, tapering 
at one end and white in colour. They are deposited mostly in ‘the stems and 
the midribs of the beet leaves. The nymphs are whitish with dark,markings 
on the dorsum. .There appears to be only one generation a-year. ‘The adults 
appear in the fields in the spring and deposit their eggs in the ‘beets. They 
will breed in’a number of native Chenopodiacex besides the Sugar beet, including 
Atriplex, Russian Thistle, Sarcobatus, &c. They have been found on several 
weeds that are not Chenopodiaceew. The life history of this insect in California 
is now being studied by Severin, of the State University, and Stahl, of the 
United States Bureau of Entomology. ; ; 
“Foreign Collector, Insectary Division, Californian Commission of Horticulture. 
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