644 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
excrement which glistened in the sunshine. When a person walked past 
one of the weeds, so that a shadow was thrown on the plant, a swarm of 
hoppers flew up. Nymphs were still abundant on sugar beets with 
green innermost leaves and dried outer foliage. Our next visit to these 
beet fields on July 5 showed that most of the insects had left saltbushes 
and that a summer migration had occurred. Another assemblage of the 
leafhoppers was observed on Bractscale on July 26. 
Fungus Diseases. —In years with an abundance of rainfall fungus 
diseases may play an important role in the reduction in numbers of the 
pest in certain parts of a natural breeding ground, such as the northern 
part of the San Joaquin Valley (4). It was found, however, in the fog 
belt of two counties that the beet leafhopper succumbed to a fungus 
disease during the dry season (5). 
Rainfall. —The writer (3) has published the fact that heavy rainfall 
kills some of the beet leafhoppers, but in all probability, is a minor factor 
in the reduction of the number of adults. 
Predicting Outbreaks 
According to Ball (1) “any information by which the probable occur¬ 
rence of these periodic outbreaks could be foretold would, therefore, be 
worth millions of dollars to this industry. It is probably more important 
to be able to say that there will be no flights to a given region during a 
season than to predict the probability of such occurrence.” 
It is evident that accurate predictions can be made in the reduction in 
numbers of the spring brood beet leafhoppers in a natural breeding area 
with the early drying up of the pasture vegetation. This prediction 
can be made safely during March: This information, however, is of no 
practical value in the interior regions of California, where early planting 
should be practiced. In the fog belt, where late planting should be 
practiced, the information may be of practical importance. 
If the factors associated with an increase of the beet leafhopper were 
accurately determined, the prediction of an outbreak of the pest could 
not be made until after the spring brood hoppers appear on the plains 
and foothills. The prediction can be made safely during April, in 
natural breeding grounds, but in the interior regions of California the 
beets would have been planted previous to the spring dispersal, if early 
planting was practiced. The information in regard to the presence of 
large numbers of hoppers on the plains and foothills would be of no 
accurate value in the fog belt, for the insects will not invade the coast 
regions, if fogs are present at the time that the spring flights occur, but 
will enter this area when fogs are absent. 
