October, '22] schwing and hartung: beet leafhopper 367 



and at the end of the season a crop of less than one ton per acre was 

 harvested. Beets planted in January, 1921 in the same field averaged 

 eight tons per acre. On a second tract planted about the last of March, 

 1920 the beets were still unthinned when the spring brood made its ap- 

 pearance. Blight made quick inroads on this area also, amounting to 

 100% by July 24. The yield from this field was 3.1 tons per acre which 

 hardly paid for harvesting the crop. A third tract was planted in 

 February. When the bugs appeared, these beets were making a thrifty 

 growth and continued to grow but did not show the effect of curly leaf 

 until much later in the season. These beets did not show 100% blight 

 until August 20, and before that time they were ready to harvest. 

 Even though a delay of the last irrigation due to power shortage reduced 

 the crop, a yield of over seven tons per acre was secured from this field. 



In the fog belt districts more leafhoppers were present and a higher 

 percentage of curly leaf occurred in early planted beet fields than in 

 fields planted after the invasion of the pest had occurred in the Salinas 

 Valley. March plantings showed 80% curly leaf on July 23, near Chua- 

 lar, while beet seeds which germinated after May 1, showed only 3% 

 blight on August' 5. At Santa Rita 60% of the early planted beets were 

 blighted compared with 3% in an area replanted on account of the disease 

 in the same field. The same condition occurred in the San Juan Valley; 

 where, on one side of the river, March and April plantings were destroyed 

 by curly leaf, while on the opposite side of the river late plantings 

 produced a good crop. 



The two following questions are frequently asked by growers: (1) 

 Can a profitable crop of sugar beets be grown where the beet leafhopper 

 is present' (2) Will it pay to allow beet fields that are attacked by 

 leafhoppers to complete their growth, or is it advisable to plow up the 

 beets and plant some other crop? Systematic observations show that 

 under semi-arid conditions near King City, Salinas Valley, beets planted 

 before March 1, with proper cultural methods and soil moisture, will 

 produce a fair yield in blight years. If beets have not been thinned 

 or have just been thinned, when the adults invade the fields, the possibili- 

 ty of a crop is very problematical; in fact, a failure is almost a certainty 

 when one leafhopper to 20 beets are present. If the beets have been 

 thinned and possess not over 16 leaves, with the same nimiber of insects, 

 the crop is still doubtful and the beets may or may not pay for harvesting. 

 In the case like the latter, beets had best be left to complete their 

 growth if there is doubt as to the success of a crop planted at this time. 

 In the fog belt districts of the Salinas Valley where climatic conditions 



