42 SOME INSECTS INJURIOUS TO TRUCK CEOPS. 
worse throughout the season. The only explanation found for that 
condition was that, while the beet had plenty of water, still the top 
soil was dry and dusty, and the ground was as hot as in an ordinary 
field, while in the fields that were irrigated early the evaporation from 
the moist surface kept the temperature down until the beets were large 
enough to shade the ground. This would also explain the fact that 
everywhere in the State, except in Sevier County, the late beets were 
affected much worse than the early ones. In other portions of the 
State the early beets were large enough to shade the ground in the 
rows by the time the hot weather and leaf hoppers appeared. In 
Sevier County, on the other hand, the hot, dry weather came on 
earlier and the leaf hoppers were so much more numerous that even the 
earliest beets could not withstand their attack when exposed to the 
full force of the sun. 
The unusual numbers of the beet leafhopper were apparently 
largely the result of a winter and spring favorable for the preserva- 
tion of insect life, as almost all injurious insects were present in in- 
creased numbers during that season (1905). The leafhoppers had, 
however, evidently been increasing for several years and had even 
before this reached destructive numbers in Sevier County, as the 
beet growers there had been suffering increasingly from what they 
called " blight " for two years previous to this, and this increase in 
the number of insects, followed by a winter favorable to their sur- 
vival, resulted in the outbreak of 1905. 
The leafhoppers were present in every field examined in Utah that 
season, and occurred in the greatest abundance in the areas in which 
the " curly-leaf " was worst. The average number of adults of the 
over-wintered brood to a beet varied from 3 or 4 up to 10 or 15, and 
probably even more than that in Sevier County, judging from the 
number found there later. No serious damage was done where there 
were only the smaller numbers, and even where the damage was worst 
it seemed to depend more upon how early they appeared and the tem- 
perature and moisture of the locality at that time than on the actual 
number above an average of possibly 5 or 6 to a beet. In 1906 they 
appeared in very small numbers. The field at Lehi, Utah, where the 
experiments were conducted, was by far the worst found, and here 
they averaged only about 1 or 2 to a beet, while the average of the 
valley would not have been more than 1 to every ten or fifteen beets, 
and the average of the State was even less. 
A field in Boxelder County, Utah, was examined in August, 1905, 
in which the leafhoppers had recently appeared in large numbers, 
averaging 100 or even 200 in some places to the beet. The beets were 
large enough then to shade the ground, and the field was well irri- 
gated from that time on. Almost no curling of the leaves could be 
! 
