LEAFHOPPEES OF THE SUGAR BEET. 43 



found in this field, and in the fall the yield was nearly up to the 

 average. This was the only field examined in which the leafhoppers 

 did not appear until after the adults had hatched out. On the other 

 hand, manj^ fields were examined in Avhich the leafhoppers had been 

 present early in the season but had almost disappeared after the 

 nymphs had matured, and yet in these fields the curling continued 

 to develop throughout the season and the beets grew worse instead of 

 recovering. 



Sprajdng with kerosene enudsion was tried on a field in the Cache 

 Valley, Utah, in 1905. This field contained numerous adults and 

 nj-mphs in all stages. Four nozzles were used, each one set about 18 

 inches above the row and pointing obliquely down and forward, and 

 just in front of them a bar drew the beet tops over and caused the 

 leafhoppers to jump just as the spray struck them. 2\ji emulsion 

 diluted with 15 parts of water had little etfect on the adults, and 

 only killed a fcAV of the smaller nymphs. Most of the nymphs would 

 kick about on the ground and some would become quite still, but a 

 little later most of them would recover and hop away. An emulsion 

 diluted with 8 parts of water produced the same effect on the adults 

 that the weaker dilution did upon the n3^mphs, and killed the ma- 

 jority of the nymphs that it struck. Many of the latter would, how- 

 ever, escape the spray on account of the broad leaves of the beet, and 

 the results were not considered entirely satisfactory. 



In the cage experiments it was expected that the number of leaf- 

 hoppers necessary to cause "curly-leaf" on different-sized beets 

 would be ascertained, but owing to the fineness of the gauze neces- 

 sary to hold them the temperature and moisture could not be con- 

 trolled and no " curly-leaf " was produced." The damp conditions of 

 the cages also made it difficult to keep the insects for any length of 

 time. 



In one experiment 1(5 leafhoppers, 12 of which Avere females ready 

 to deposit eggs, were placed on a beet with a top 8 inches in diameter 



«This manuscript was originally prepared and submitted at tlie close of the 

 season of 1906. Some i-evision was made to include the important facts of the 

 work of 1907, but the main discussions, including the above paragraph, were 

 written in 1906. Since that writing " curly-leaf " has appeared in cages arranged 

 by I'rof. E. G. Titus in joint investigations with the writer.' Mr. H. B. Shaw, 

 assistant to Dr. C. O. Townsend, in charge of Sugar P.eet InvestigaticMis. BnroiUi 

 of Plant Industry, U. S. Department of Agriculture, has also succeeded in pro- 

 ducing " curly-leaf" under exiierimental conditions. lie writes me under date of 

 October 23, 190S, that curly top or "curly-leaf" appeared in the cages on the 

 experimental plat at Garland, Utah, in which he introduced the beet leaf- 

 hoppers, and that later he sent a number of leafhoppers to the office of Sugar 

 Beet Investigations, Bureau vf IMant Industry, where of them were placed in 

 a cage with 11 young beets, 9 of which showed distinct symptoms of " curly- 

 leaf " wif hin tive weeks after the insects were introduced. 

 66— IV 



