208 The Spraying of Plants. 



a strong solvent action upon soft brass, that which is composed 

 of copper and zinc, and for this reason such brass should be 

 avoided. Hard brass is an alloy in which more or less tin is 

 used with the copper ; it is much more durable, and is to be 

 preferred in the construction of both pumps and nozzles. 



Pump valves are made of various materials. The metal ones 

 are to be preferred as a rule, although glazed ball valves are 

 very satisfactory. Leather is freely used as packing and in 

 valves, and on account of the ease with which it can be 

 replaced, it is not objectionable. Rubber, however, especially 

 if it is soft, is unsafe to use in a spray machine. Kerosene will 

 cause it to swell to such an extent that the pump is rendered 

 worthless until a new valve is put in, or the old one is given 

 time to shrink, a process which may require months. 



Knapsack pumps have several features to recommend them. 

 Liquids can in this manner be carried and applied in places 

 inaccessible to wheeled vehicles. Vineyards are frequently set 

 in such locations, as are also espaliers and fruit-walls, and under 

 such conditions a knapsack pump has no equal. On small home 

 grounds, where the nature of the spraying is varied, these 

 pumps may also be used to advantage. But trees cannot be 

 successfully treated by them, as the liquid is not thrown far 

 enough. Nor is their use in even moderately large plantations 

 advisable, since the labor of carrying the pump is onerous, and 

 the machine is not easily operated. Other unpleasant features 

 will also be forced upon the man who works the machine, and 

 when possible a different device should be preferred. 



Hand syringes are practically out of the question when liquid 

 applications are to be made, except in case of plants grown 

 under glass; then the syringe is much used, although water 

 under pressure is now so generally piped to greenhouses that 

 even here the use of syringes is steadily decreasing, the more 

 so, since a stream of water forcibly applied is a very popular 

 way of controlling insect pests. Fungicides may be applied to 

 plants under glass, either with syringes or by means of knap- 

 sack or bucket pumps. 



Bucket pumps, such as represented in Fig. 24, are very power- 

 ful for their size, and they will throw considerable quantities 

 of liquid. Moderate-sized trees may be thoroughly treated by 

 them, and when little work is to be done these pumps may well 



