ENTOMOLOGY 385 



of the spraying apparatus now on the market are provided with 

 automatic agitators. 



Selection of Spraying Outfit. For limited garden work or for 

 the treatment of low plants a simple bucket pump can be used 

 which will cost about $6, or the knapsack pump, costing about $14. 

 For home orchards of small size a barrel pump with one line 

 of hose will serve every purpose, the complete outfit costing $12 to 

 $18. For larger operations, with two lines of hose and nozzles, 

 a barrel outfit, costing from $25 to $30, may be used. Tank out- 

 fits, with double cylinder pumps suitable for an orchard of a thous- 

 and bearing trees, may be obtained at a cost of from $75 to $90. 

 The power sprayers are quite expensive, costing $200 to $300 or more. 



Directions for Spraying. Thorough work in spraying must be 

 done, or failure will result. To accomplish this, power sufficient to 

 break up the liquid into a fine mist is essential. This makes it pos- 

 sible for the tree to be thoroughly and thinly wetted with the spray 

 without waste, and the ideal application is to accomplish this with- 

 out causing the liquid to collect in drops and fall from the tree. 

 More of the spray is left on the leaves with a light spray than with 

 a heavy application, which causes the globules to coalesce and a 

 shower of drops to fall to the ground. To get a proper spray, it 

 should be possible to produce a pressure of at least 75 pounds, or, 

 with power outfits, of 125 to 150 pounds. 



Fruit trees of average size or, if apple, such as would produce 

 10 or 15 bushels of fruit, will require from 3 to 7 gallons of spray 

 to wet them thoroughly. For smaller trees, such as plum and 

 cherry, 1 gallon to the tree may be sufficient. In spraying orchard 

 trees and other fruit trees it will often be found convenient, es- 

 pecially with a smaller apparatus, to spray on each side half of each 

 tree in a row at a time, and finish on the return. A light rain will re- 

 move comparatively littie of the poison, but a dashing rain may 

 necessitate a renewal of the application. 



Hydrocyanic-acid Gas Treatment. The use of hydrocyanic- 

 acid gas originated in southern California in work against citrus 

 scale insects, and was perfected by a long period of experimentation 

 by an agent of this Bureau, Mr. D. W. Coquillett. It is undoubtedly 

 the most thorough method known for destroying scale insects and 

 especially is it the best treatment for citrus trees, the abundance of 

 foliage and nature of growth of which render thorough spraying 

 difficult, but, on the other hand, enable the comparatively heavy 

 tents employed in fumigation to be thrown or drawn over the trees 

 rapidly without danger of breaking the limbs. One good gassing is 

 usually the equivalent of two or three sprayings, the gas penetrating 

 to every particle of the surface of the tree and often effecting an 

 almost complete extermination, rendering another treatment un- 

 necessary for two years or more. 



Another very important use for hydrocyanic-acid gas is as a 

 means of controlling insect pests in greenhouses and cold frames. 

 The process is a special one, however, and entails considerable vari- 

 ation, owing to the wide range of plants to be considered. A more 



