142 
WILLOW. 
in this case it only knocks or frightens the beetle out of the way of 
what is meant gradually to kill it. It should be sent as a spray, to rest 
like a dew evenly all over the surfaces of the leafage, so that, unless 
the beetle flies elsewhere, it has no resource but to eat the poisoned 
food ; and if the spraying is as complete as it should be, the dew will 
rest on the under as well as the upper surface of the leaves, and avail 
in destroying the grubs as well as the beetles. 
Another point mentioned as a difficulty was “ the Willows by 
this time were grown three feet high; therefore he could not apply a 
good spray ; but the application to the plants on the compass of ground 
sprayed with Paris-green was successful.” 
By means of the knapsack sprayer, which was successfully used at 
the Toddington Fruit Ground last year, the spray can be sent to a height 
of fourteen or fifteen feet, and properly distributed.”* 
So far as the more practical work of application of the Paris-green 
is concerned, it will be seen that the above notes of advance in 
information, since our experiments of 1884 were tried, will meet the 
difficulties which then encumbered us. Looking at the amount of 
success which we then had, and also considering that Paris-green is 
the especially approved application in America, and has been so for 
many years, and over thousands of miles, for keeping down the 
Colorado Potato Beetle (which, being one of the Chrysomelidce , is very 
nearly allied to our Willow Beetle),—these points appear to suggest 
forcibly that it would be well worth while to try again, with the lesser 
strength and the better spraying machines, whether we could not get 
rid of the Willow pest when it appears. 
All the requisite cautions to be considered in the use of Paris-green, 
it being arsenite of copper and consequently a poison, and all requisite 
instructions as to methods of use, are given in the preceding pages, 
under the head of Paris-green; also notes of another arsenical 
insecticide, “arsenite of lime,” sold under the name of London-purple, 
in the use of which similar precautions and methods of application are 
to be observed. It should, however, be always borne in mind that for 
safety to leafage, in the case of insecticides of which the effect is not 
wholly known to the applier, experiment should be made on a small 
scale to a few trees or plants, and the results watched for a few days, 
and their effect ascertained beyond all doubt, before proceeding to try 
them on a scale that may at liap-hazard greatly benefit, or greatly 
injure, acres of tree or plant growth. 
* Information regarding this form of spraying machine will be found at p. 99 
preceding, under the heading of Paris-green. 
