; - 12 = 
fields as abundantly as 24 to 29 per cent, but most fields are but little 
injured." This "lack of injury on beans is difficult to explain in view 
of that occurring on beets. It appears likely, however, that the differ— 
ence between last year's injury and this year's may be explained on the 
basis of size ot the initial migration, as the insects appear to remain 
in bean fields only a limited time." 
In their work with egg parasites of the leafhopper Mr. Henderson 
and his assistants have found that the efficiency of these parasites is 
limited by the lack of proper host-plant sequence in the known desert 
breeding grounds. "The distribution of the two spring host plants of 
Eutettix tonellus, Sophia sophia and Norta altissima, is not identical 
with that of the summer and fall host, Salsola pestifer. Consequently the 
great bulk of egg parasites, upon emerging from dry §. pestifer in the 
spring, are not located in the large breeding areas of E, tenellus, and by 
the time they have become established and have reached sufficient numbers, 
practically all the eggs of E. tenellus which give rise to the first 
brood have hatched. A study of host-plant sequence is therefore essen— 
tial in determining the limitations of the egg parasites now present and 
in addition will furnish important information relative to the introduc— 
tion of any foreign species." 
F. R. Lawson, Davis, Calif., has been working out methods for 
making a rapid survey of the extent of summer weed hosts of the beet leaf-— 
hopper in the San Joaquin Valley. W. C. Cook, in charge of the Davis sub— 
laboratory, says: "He (Mr, Lawson) has adopted a method based on linear 
miles of vegetation seen on both sides of the road in traveling. * * * 
At the present time he estimates 25,000 acres of weed hosts in Stanis— 
laus County." : 
Mr. Cook also reports the checking of some experiments conducted 
by a California commercial spray company, "with a new type of machine 
which applies oil in the form of a fine fog, using air as a distributing 
agent instead of water. On July 21 a spray of light oil containing 10 
per cent pyrethrum extract was applied on a thick stand of Atriplex brac— 
teosa, south of Modesto. Mr. Schwing and myself checked the area before 
and after spraying and found that about a 95 per cent kill was obtained, 
using between 4 and 5 gallons of material to the acre. On July 31 some 
more extensive experiments were performed in the presence of the writer 
and Mr. Schwing. Several combinations of different oils with different 
amounts of pyrethrum and without pyrethrum were tried on beets which had 
high populations of bugs. A light oil, 5 per cent pyrethrum extract, 
gave 56 per cent control, with 6 2/3 per cent pyrethrum gave 59 per cent 
control, and with 10 per cent pyrethrum gave 95 per cent control. This 
last spray was at the rate of about 8 gallons per acre. These figures 
were checked by taking sets of 10 collections before spraying and again 
about one hour after the spray was applied. About a dozen cages of bugs 
exposed in different patches showed that the 10 per cent pyrethrum spray 
would give 100 per cent mortality, and also that the bugs would not again 
come to life. A spray with 2.3 per cent nicotine instead of pyrethrum gave 
about 50 per cent control, while the straight oil gave 30 per cent control. 
These results indicate that this method of application of oil shows con- 
Sp ala a em wa. 
