PROTECTING PLANTS 191 
kill by destroying the body of the insect. Of the former, there 
are three materials in common use — Paris green, arsenate of 
lead, and hellebore. Of the latter, the most usual at present 
are kerosene emulsion, miscible oils, and the lime-sulfur 
wash. In the last year or two, the lime-sulfur preparations 
have been greatly perfected, and they are now becoming popu- 
lar in commercial work not only for insects but for certain fungi. 
Sprays for fungi usually depend for their efficiency on some 
form of copper or sulfur, or both. For surface mildews, as 
grape mildew, dusting flowers of sulfur on the foliage is a pro- 
tection. In most cases, however, it is necessary to apply 
materials in liquid form, because they can be more thoroughly 
and economically distributed, and they adhere to the foliage 
better. The best general fungicide is the bordeaux mixture. 
It is generally, however, not advisable to use the bordeaux 
mixture on ornamental plants, because it discolors the foliage 
and makes the plants look very untidy. In such cases it is best 
to use the ammoniacal copper solution, which leaves no stain. 
In all spraying operations it is especially important that the 
applications be made the very moment the insect or disease is 
discovered, or in the case of fungous diseases, if one is expecting 
an attack, it is well to make an application of bordeaux mix- 
ture or lime-sulfur even before the disease appears.. When the 
fungus once gets inside the plant tissue, it is very difficult 
to destroy it. For ordinary conditions, from two to four spray- 
ings are necessary to dispatch the enemy. In spraying for 
insects in home gardens, it is often advisable to make a sec- 
ond application the day following the first one in order to 
destroy the remaining insects before they recover from the 
first treatment. 
There are many kinds of machines and devices for the ap- 
plication of sprays to plants. For a few individual specimens, 
the spray may be applied with a whisk, or with a common garden 
syringe. If one has a few trees to treat, however, it is best to 
