Pe^ts and Diseases 197 



on seed, heating that seed to a dry temperature of 145° F. 

 will kill any nematode without injuring the seed. 



The beet leaf hopper (Evtettijc tenella Baker). 



This is probably the most serious pest of the western 

 sugar-beet. Plate XXIII. It causes injury through the 

 disease curly-leaf, which it transmits. This disease, to- 

 gether with all other similar leaf troubles, has gone under 

 the general name of "curly top." For many years the 

 cause of this important disease was not known, but the 

 discovery that it is due to punctures made in the leaf by 

 the beet leafhopper makes clear the source of the difficulty. 



"Attention ^ was first called to the trouble in 1899 and 

 1900, when it appeared throughout the entire western 

 region from California to Nebraska. Another serious 

 outbreak occurred in 1905. Over the large part of the 

 area it has only appeared two or three times in twenty 

 years. In smaller areas it has usually appeared in three- 

 year attacks, cumulative in nature, after which it has 

 almost totally disappeared for a time. In still other 

 areas it has appeared the greater part of the time, and in 

 these areas beet-raising has not been successful. 



"This insect is single-brooded, hibernates as an adult, 

 flies to the beet field in late spring, and lays eggs in beet 

 stems — a few at a time until mid-summer. The larvae 

 mature in summer and the adults disappear in early fall. 

 It is found on shadscale, greasewood, Russian thistle, 

 and fine-leaved annual salt bushes. Swarms of these 

 insects appear suddenly in beet fields previously unin- 

 fested. Much evidence points to the conclusion that these 

 1 BaU, E. D., Utah Exp. Sta., Bui. No. 155 (1917). 



