42 SOME INSECTS INJURIOUS TO TRUCK CROPS. 



Avorse 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 leaflioppers appeared. In 

 Sevier County, on the other hand, the hot, dry weather came on 

 earlier and the leaflioppers 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 leaf hoppers 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 leaflioppers 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 Lelii, 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 leaflioppers 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 



