THIRD ANNUAL REPORT OF STATE ENTOMOLOGIST. 205 



appear over such a greatly protracted period, the larvae are hatch- 

 ing- and entering the fruit through practically all summer. A much 

 larger per cent, therefore, can be killed by an insecticide which when 

 once applied remains on the trees through a long season. Contain- 

 ing as it does a very small amount of soluble arsenic this compound 

 may be applied even to delicate foliage like that of the plum in 

 much greater strengths than Paris green. A third point in its favor 

 is that being white in color the operator can plainly see just what 

 trees or parts of trees have been sprayed. This is particularly 

 desirable in some classes of work where one gang of workmen with 

 a power outfit goes over a large number of trees leaving another 

 party to cover the parts of the trees omitted, thus making a very 

 thorough job at a minimum expense. 



Other arsenical compounds are in use but they are not to be re^ 

 commended for the general fruit grower in competition with Paris 

 green and arsenate of lead, 



SPRAYING MACHINERY AND APPLIANCES. 



From the orchardists' standpoint there are two classes of 

 pumps, namely, first, those which are worked by hand and second 

 those in which some form of power is used. It is very desirable 

 that a good strong pressure be maintained in the fluid and with 

 power outfits more ground can be covered and with greater 

 thoroughness. A good man power outfit is sufficient for an orchard 

 of about 2,000 trees or less. For orchards above this number a 

 power outfit should be selected from among the various types that 

 can be secured. 



Anew style of sprayer is attracting attention in the East and 

 has the approval of some parties wdio are spraying on an extensive 

 scale. In this outfit no pump is used but the pressure on the fluid 

 is maintained by the use of liquefied carbonic acid gas. The air tight 

 metallic tank containing the spraying mixture is connected to a 

 smaller tank or tube containing the lipuefied gas. When the valve 

 between the two tanks is opened sufficient pressure is produced 

 above the spraying fluid to force it out through pipes taken from 

 the bottom of the tank. It is said that a sufficient and an even pres- 

 sure can be maintained. In the use of this outfit much depends 

 upon the price of the liquefied gas in Montana. The best figure 



