Report of the State Entomologist 293 



water. Constant agitation is very important in using this arsenite — 

 far more so than with the lighter powder of London purple. From 

 an experiment just made by me, it was found that a mixture of one 

 pound of the Paris green uniformly distributed by stirring in two 

 hundred gallons of water and then permitted to rest, would in thirty 

 seconds give a mixture drawn from the bottom through the spraying 

 pipe of a strength of about one pound to sixty gallons of water — far 

 too strong for most foliage. London purple should first be mixed 

 with a little water into a paste-like consistency, and then washed 

 through a fine wire sieve into the tank that such impurities may be 

 removed as might otherwise clog the finer spraying nozzles." 



In using smaller pumps, such as maiy be placed in a pail or open 

 vessel, as the Combination Force Pump of P. C. Lewis, Catskill, N. Y., 



Fig. 22.— The Lewis Combination Force Pump, in one of its forms. 



one of the forms of which is shown in Figure 22, the required mixture 

 of the Paris green may be accomplished by withdrawing the hose 

 from the tree at short intervals, and directing its nozzle into the 

 vessel for two or three seconds while the pumping is continued. 

 Beneficial Results of Spraying. 



As illustrating the benefits resulting from arsenical spraying for 

 prevention of curculio injury, we may refer to the experiments made 

 by Dr. Otto Lugger, Entomologist of the Minnesota Agricultural 

 Experiment Station, in spraying native plums, which are often spoken 

 of as being curculio proof.* 



The first work of the curculio was noticed on June 4th; on the next 

 day two trees each, of from ten to twelve feet in height, of three 

 different varieties, were sprayed by th^ aid of a common garden 

 syringe with one spoonful of London purple to two gallons of water, 

 just after the blossoms had fallen, and twice thereafter at intervals of 

 a week. 



As the result, the ripe fruit on the sprayed trees was almost entirely 

 free from blemishes, was of unusually large size, well colored and of 

 high flavor. The unsprayed trees used as checks, contained hardly a 

 plum that was not injured by the curculio or by the plum-gouger, 

 while the fruit ripened prematurely and was of smaller size and 

 inferior flavor. The foliage of the syringed trees was uninjured. 



* Bulletin No. lo, March, 1890, Minnesota Agricultural Experiment Station. 

 38 



