LEAFHOPPERS 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, many fields were examined in Avhich the leafhoppers had been 

 present early in the season but had almost disappeared after the 

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

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

 recovering. 



Spraying with kerosene emulsion was tried on a field in the Cache 

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

 nymphs in all stages. Four nozzles Avere 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 spraj^ struck them. An emulsion 

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

 only killed a few 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 awa}'. An emulsion 

 diluted with 8 parts of water j)roduced the same effect on the adults 

 that the weaker dilution did upon the nymphs, and killed the ma- 

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

 ever, escape the spraj^ 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 16 leafhoppers, 12 of which were 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 the close of the 

 season of 1906. Some revision was made to Inchide the important facts of the 

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

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

 by Prof. K. G. Titus in joint investigations with the writer. :Mr. II. B. Shaw, 

 assistant to Dr. C. O. Townsond, in charge of Sugar Beet Investigations, Bureau 

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

 ducing " curly-leaf " under experimental conditions. He writes me under date of 

 October 23, 1908, that curly top or "curly-leaf" appeared in the cages on the 

 e.xporimental plat at Garland, I'tah, in which he introduced the beet leaf- 

 hoppers, and that later he sent a number of leafhoi)pers to the office of Sugar 

 Beet Investigations, Bureau cf IMant Industry, where (! of them were placed in 

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

 leaf " within five weeks after the insects were introduced. 



