SPRAYING 57 



sporiaceae, as the hop mildew, pea mildew, etc. There are 

 various contrivances on the market for depositing the 

 powder on the foliage, which should be damp at the time of 

 application. When required on a small scale, as for a row 

 of peas, etc., ' flowers of sulphur ' may be placed in a coarse 

 canvas bag which is fixed to a pole, and dredged over the 

 affected plants. 



The following deal with spray mixtures generally, and give 

 the mode of preparation of numerous different solutions used 

 against fungi and insects. 



Beach, S. A., Clark, V. A., and O. M. Taylor, N.Y. Agric. 

 Expt. Sta., Bull. No. 243. 



Pickering, Spencer V., F.R.S., Eighth Report of the Woburn 

 Exp. Fruit Farm (1908). 



SPRAYING 



In spraying plants the ideal to aim at is the production of 

 a ' London fog ' that settles on the foliage as a dense mist, 

 forming minute particles of water that gradually evaporate, 

 and leave on the surface of the foliage a uniform layer of the 

 substance held in solution. 



Spray solutions are preventive in their action, and not 

 curative. They may check the occurrence or the extension 

 of a disease, but they cannot cure a plant of a disease caused 

 by a fungus, the mycelium of which is already in the tissues 

 of the leaves. The object of applying a spray to a plant is 

 to cover the surface of the foliage and other susceptible 

 parts with a substance that will kill the germ-tubes of all 

 fungus spores alighting on the surface of the leaves, etc., 

 so that the mycelium cannot enter the living tissues. To 

 effect this object every portion of the plant liable to infec- 

 tion should be covered with the fungicide. This is the 

 goal, which has not been reached as yet. Some spraying 

 machines, if properly handled, do much better than others, 

 but I have never yet seen a spraying apparatus, however well 

 managed, that produced the desired result, yet when spraying 

 is done by an experienced hand, and with the machines now 

 in vogue, an epidemic can be prevented. 



The relative fineness of the spray depends mainly on two 

 things: (1) The amount of pressure. A very much finer 



