316 EXPERIMENT STATION— BULLETINS. 



NO. 53.— ENTOMOLOGICAL DEPARTMENT. 



SPRAYING WITH THE ARSENITES.* 



Me. President — 



Nine years ago, at the first meeting of this society, I presented a paper 

 upon the use of Paris green as a specific against the codling moth. 



In that paper I gave the results of careful and elaborate experiments, 

 which settled two facts that were very important in economic entomology: 

 First, that Paris green was efficient as a preventive of the ravages of the 

 codling larva; and secondly, that such use was entirely safe in respect to 

 poisoning the fruit. Today, less than a decade from the date of the dis- 

 covery of this remedy, this method to combat the worst insect pest of the 

 apple grower is generally adopted by the more intelligent orchardists of our 

 country. Its value is now universally conceded. Easy and cheap methods 

 to apply the insecticide are now known and generally adopted, f 



For several years myself and others have been experimenting, in hopes to 

 find that this same insecticide was equally efficient to destroy the plum 

 curculio. For six or seven years I have sprayed plum trees once and even 

 twice with no apparent good. Test trees, close beside the trees sprayed, 

 and that were not treated, were as free from attack as were the trees that 

 were sprayed, and the trees treated were no more exempt from attack than 

 the others. Thus I was convinced that this insecticide was of no value in 

 this curculio warfare. Several of my horticultural friends, in whose ability 

 to experiment and observe correctly I had great confidence, had tried this 

 remedy with very satisfactory results. In 1888 I studied this matter very 

 closely, and concluded that as the plum is a smooth fruit, with no calyx 

 cup like that of the apple, in which the poison may lodge, and as the 

 curculio lays its egg anywhere on the smooth rind, the poison would be very 

 easily washed off, or even blown off by the wind. I thus concluded that my 

 want of success was very likely due to a want of thoroughness. In 1888 I 

 sprayed certain trees three times, at intervals of eight days, and omitted to 

 treat other trees close alongside. The benefit from spraying was very marked. 



I also found that carbolized plaster — one pint of crude carbolic acid to 

 fifty pounds of plaster — was quite as efficient to repel the curculio as was the 

 arsenites. This was also applied three times. The season was very dry, 

 and there were few or no rains to wash off the insecticides. This year I 

 repeated the experiments both with the London purple and with the carbol- 

 ized plaster, but with no success. All the trees were severely attacked, and 

 all the plums lost. This year we had almost daily rains, which were fre- 

 quently quite severe. 



* Read at Toronto, August 26, before the Society for the Promotion of Agricultural Science. 



t A very cheap and excellent pump, not mentioned in Bulletin No. 39, issued by the Michigan 

 Experiment Station, of last year, is the Brooks Braes Hand-force Pump, and is sold for $2.00, by Mr. 

 J. K. Compton, Leslie, Michigan. For a few trees it serves very well. 



