AKTIFICIAL CONTROL. 43 
careful, clean cultivation, so that all weeds may be kept down in 
the fields at all times, including the spring and fall. These same 
weeds, especially the different species of wild lettuce, should be care- 
fully destroyed along the edges of all fields and fence corners and 
along the roads and railroad tracks. Cotton and beans should not 
follow in old alfalfa fields if the latter were badly infested with the 
bean thrips, and fields of these crops should be removed as far as 
possible from the alfalfa fields. They should also be planted as 
early as is consistent with good farming and encouraged by fre- 
quent cultivations and fertilizers where necessary to produce an early 
crop so as to escape the ravages of the bean thrips in the late summer. 
As this insect feeds on such a variety of plants it is hardly pos- 
sible that rotation of crops would aid materially in its control unless 
some crop could be found that is quite immune. 
Where it is injuring alfalfa Mr. Wildermuth recommends disking 
and thorough renovation of the fields and good irrigation in order 
to give the plants as much chance as possible to make a quick growth. 
SPRAYING. 
The control of this thrips by spraying is impracticable for a crop 
such as alfalfa or cotton, and because of the low trailing vines of 
the bean will probably be successful with this plant only when the 
vines can be easily reached from the underside. In case injury to 
fruit trees is threatened it can be controlled by using the spray so 
successful against the pear thrips. This is a solution of 2f per cent 
nicotine, diluted at the rate of 1 part to 60 parts of water in a 6 
per cent distillate-oil emulsion. 1 
The distillate-oil stock emulsion, according to the formula of 
Foster and Jones, is made as follows : 
Hot water • gallons__ 12 
Fish-oil or whale-oil soap pounds 30 
Distillate-oil (raw) 30° to 34° Banme gallons__ 20 
Have the water boiling hot when put into the spray tank and add the soap 
immediately while the agitator is running at a good speed. When the soap is 
all thoroughly dissolved pour in the oil slowly, keeping the mixture well agi- 
tated while the oil is going into the tank. When all of the oil is in and well 
mixed, pump out through the nozzles at good pressure (not less than 175 
pounds) into storage tanks. 
No one should attempt to make this stock emulsion without a power spraying 
machine, as thorough agitation and high pressure are important requisites. 
Also, care should be used in having measurements reasonably exact, the water 
boiling hot, and the soap thoroughly dissolved before any oil is put in. This 
stock solution contains approximately 55 per cent oil, and to make a 3 per cent 
emulsion use 5J gallons of this stock in each 100-gallon tank. 
1 For a full account of this spray as used against the pear thrips, see Circular 131, 
Bureau of Entomology, U. S. Dept. of Agriculture, pp. 8-9. 
