406 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



valleys and in all probability, when beet fields are not isolated invasions 

 from, field to field occur. On the other hand, most of the adults which 

 fly into the beet fields during the spring are females which have mated 

 on the plains and foothills and in all probability, the females at the 

 egg-laying stage make only short flights from, beet to beet for the purpose 

 of disseminating the eggs. The percentage of curly leaf increases rapid- 

 ly with the appearance of the summer generations which is not the case 

 when the spring brood invades the beet fields unless the pest is unusually 

 abundant. It is evident that no conclusions should be drawn as to the 

 value of the dust preparations against the summer broods, and dust 

 mixtures should be tested when the spring brood first makes its appear- 

 ance in the beet fields. 



During 1920, a Niagara dusting machine was remodeled and various 

 types of dusting nozzles enclosed in a sheet-iron fumigation box were 

 tested. One type of nozzle terminating in two flattened tubes (PI. 5 fig. 

 2) blow the dust toward the lower surface of the leaves of two rows of 

 beets. The nozzle which terminates in the funnel-shaped enlargement 

 (PI. 5 fig. 2) is provided with a sieve-plate and forces the dust between the 

 petioles of the leaves. 



During the 1920 outbreak of the beet leaf hopper, an attempt was made 

 to control the pest with the use of adust mixture in a beet field near King 

 City, in the Salinas Valley. The experiment was conducted on the Ox- 

 nard tract of Ranch 3, which contained about 900 acres of beets. Two 

 lots containing 7.6 acres of beets planted in February were selected, 

 isolated on one side by foothills and surrounded on all other sides by 

 beets. One of the lots of 7.6 acres was divided into four plots and dusted 

 with "5% Nicodust" and the other 7.6 acres was divided into two plots 

 and dusted with " 10% Nicodust." "Nicodust 5% and 10%" however, 

 contain only 2% and 4% nicotine, since "Black Leaf 40" contains 40% 

 nicotine sulphate by weight. The dust was applied from 6-10 a.m. 

 before the heavy winds started to blow. The number of applications 

 and the amounts of dust per acre follows: 



May 13, plots 1, 2, 3, 4 dusted with about 50 lbs. "Nicodust 5%" 

 May 20, plots 2, 3, 4 dusted with about 75 lbs. "Nicodust 5%" 

 May 27, plots 3, 4 dusted with about 75 lbs. "Nicodust 5%" 



June 3, plot 4 dusted with about 100 lbs. "Nicodust 5%." 



Number of applications 12 3 4 



May 14, plots 1, 2 dusted with about 75 lbs. "Nicodust 10%." 

 May 28, plot 2 dusted with about 75 lbs. "Nicodust 10%." 



Number of applications 1 2 



