18 BULLETIN 160, U. S. DEPARTMENT OF AGEICULTURE. 



pound to every gallon of water used in making up the spraying 

 mixture. These proportions have given the most favorable results 

 in all experiments conducted so far. When amounts in excess of 1 

 pound to each gallon of water are used the adhesive powers do not 

 appear to be increased to any great extent, and on the other hand 

 difficulty is experienced in applying the spray, particularly where 

 very fine nozzles are employed. 



ZINC ARSENITE AS AN INSECTICIDE. 



Zinc arsenite has been used both in the paste and powder forms with 

 much success for the belted cucumber beetle, as well as for some other 

 insects of this class. It has proved to be one of the most effective 

 sprays for use in humid climates, as it appears to last longer. No 

 other arsenical has given better results, and in the majority of cases 

 the mortality has been higher than with &nj other arsenical spray. 

 The powder when used with cactus to make it adhere is to be pre- 

 ferred for general use over any arsenical now on the market. This 

 spray in the writer's opinion surpasses in lasting qualities any of the 

 arsenicals and at the same time gives a higher mortality. In action 

 it is somewhat slower than Paris green, but it gives better results in 

 the end. The writer would not recommend, however, that zinc arse- 

 nite be used on plants that are nearly ready for market, for the 

 poison does not wash off easily. 



FERROUS ARSENATE AS AN INSECTICIDE. 



Ferrous arsenate has given very good results in combination with 

 cactus to increase its adhesive powers. No serious effects from its use 

 on the most delicate foliage have been observed. The cost of the 

 product at the present time places it beyond general use as an insecti- 

 cide. The ferrous arsenate in the powder form is very easily brought 

 into suspension, requiring less time than some of the other arsenicals 

 now more extensively used to destroy biting insects. Another feature 

 in the use of this arsenical is that it remains in suspension exceed- 

 ingly well and settles very slowly to the bottom of the tank. This 

 makes it a most desirable poison for use with small sprayers not 

 equipped with agitators. 



IRON ARSENITE AS AN INSECTICIDE. 



Iron arsenite was given a trial against the belted cucumber beetle 

 only, and was found to give varying results. The powder was made 

 into a spray and applied both with cactus as an adhesive and without 

 the cactus. The iron arsenite is quite hard to bring into suspension 

 and soon settles to the bottom of the spray tank unless constantly 



