10 FARMERS’ BULLETIN 662. 
caterpillars as far as possible cremated. Some caterpillars, however, 
are likely to escape, falling from the nest upon the application of the 
torch. In using the torch great care is necessary that no important 
injury be done the tree; it should not be used in burning out nests 
except in the smaller branches and twigs, the killing of which would 
be of no special importance. Nests in the larger limbs should be 
destroyed by hand, as the use of the torch may kill the bark, resulting 
in permanent injury. 
SPRAYING WITH ARSENICALS. 
Tent caterpillars are readily destroyed by arsenicals sprayed on 
foliage of trees infested by them. Dr. H. 'T. Fernald’s careful experi- 
ments and those of Prof. Lowe in determining the amount of poison 
necessary to kill the caterpillars show that the latter are very sensi- 
tive and are killed in from two to three days by the use of Paris green 
at the rate of 1 pound to 300 or 400 gallons of water. 
Orchards or trees sprayed with arsenicals in the spring for the 
codling moth, cankerworms, or similar insects will be kept practically 
free from tent caterpillars, and this species rarely requires attention 
at the hands of the up-to-date commercial fruit grower. It will be 
troublesome in the scattered trees around the home or in the small 
orchard which is not regularly sprayed. On such trees the nests 
will likely be in evidence every spring, and during occasional years 
the caterpillars may be excessively abundant, completely defoliating 
the trees. 
Even in the small home orchard of a dozen or more trees it will be 
found highly profitable to adopt a system of spraying which will 
control not only tent caterpillars but such serious pests as the cod- 
ling moth, cankerworms, and various bud and leaf feeding insects, 
and will greatly reduce injury from the curculio. 
Any of the arsenical insecticides may be used, as Paris green, 
Scheele’s green, arsenate of lead, etc. The first two are used at 
the rate of 1 pound to 150 or 200 gallons of water, and the last at the 
rate of 2 pounds to 50 gallons of water, the milk of lime obtained 
by slaking 2 or 3 pounds of stone lime being added to neutralize any 
caustic effect of the arsenical on the foliage. Preferably, however, 
the poisons should be used in dilute lime-sulphur wash or Bordeaux 
mixture, thus effecting a combination treatment for insects and 
fungous diseases. On stone fruits, such as cherry, peach, and plum, 
arsenicals are likely to cause injury to foliage and must be used with 
caution. Onsuch trees the arsenate of lead is preferable to the arseni- 
cals, as it is less injurious to foliage, and on all trees sticks much better. 
In spraying for the tent caterpillar only, applications should be made 
while the caterpillars are yet small, as these succumb more quickly to 
poisons than those more nearly full grown, and prompt treatment 
stops further defoliation of the trees. 
WASHINGTON : GOVERNMENT PRINTING OFFICE ; 1915 
