3i8 THE ESSENTIALS OF AGRICULTURE 



410. Hand sprayers. For small orchards and garden work 

 a hand pump is recommended (Fig. 158). The knapsack sprayer 

 is useful for gardens and vineyards. For gardens of considerable 

 area a hand pump mounted upon a barrel which can be trans- 

 ported by means of a cart should be used. The pump should 

 be a force pump of considerable power, the working parts of 

 which are of such material as will not corrode from contact with 

 the chemicals. Brass alloy or porcelain linings are cheaper 

 than solid brass parts, but are less durable. 



411. Power sprayers. F*or larger plantations the size and 

 capacity of the pumps should be increased (Fig. 159). Probably 

 most orchard owners find that for an area of ten acres or more, 

 a pump driven by a gasoline engine is economical and efficient. 



A convenient-sized tank for spray mixtures is one containing 

 two hundred or two hundred and fifty gallons, the size depend- 

 ing somewhat upon the topography, as it is readily seen that in 

 an orchard or field with an uneven surface the draft will be much 

 heavier than upon level ground. 



The water supply is a very important consideration, and suffi- 

 cient reservoir capacity should be arranged to allow the con- 

 venient mixing of the materials and filling the tanks with the 

 least possible expenditure of time. In many cases, particularly 

 the first sprays for the cankerworm and codling moth, the most 

 efficient work is done within a comparatively few days, and if 

 any considerable area is to be covered, all possible haste must 

 be used. 



QUESTIONS AND PROBLEMS 



1. What experience suggested the use of sprays for the general pre- 

 vention of injury by insects? 



2. How are the feeding habits of insects related to control by spraying? 



3. What common insecticides are used to protect plants against insects 

 that consume the tissue ? 



4. How may the San Jose* scale be controlled? 



5. What methods are used for destroying aphids, or plant lice, in green- 

 houses ? on outdoor crops ? 



