DISCUSSION OF INJURIOUS INSECTS. 93 



prepared, while the tobacco water seemed more easily made by the 

 ordinary grower, which was the main reason for the preference. 



Mr. Sanderson said that he had fonnd tobacco water was more effi- 

 cient, more particularly the prepared tobacco extracts. 



Mr. Smith said that in Georgia he could not get good results with 

 tobacco dust for woolly aphis. On trees 10 to 12 years old he had 

 found living aphis an inch underneath the dust six weeks after the 

 a^jplication. This dust was analyzed and found of fair quality. 



Mr. Washburn felt esj^ecially interested in Mr. Webster's remai'ks 

 on the Hessian fly. He said that it had not been reported to him as 

 injurious in any portion of Minnesota last season. He was confident 

 that this was the state of a If airs, because he had correspondents in 

 almost every county in the Avheat-raising district, and he further got 

 clippings from all the county papers in the State, and he was certain 

 that if it had been found injurious he would have been informed 

 of it. He had claimed for several years that there might be more 

 than one brood in Minnesota in favorable seasons, and Mr. Webster's 

 corroboration of this as regards North Dakota was gratifying. 



Mr. Sanderson, referring to Doctor Felt's statement regarding 

 Pemphigus acerifolii, said that while this had formerly been re- 

 garded as a rare insect, it was certainly not now rare in some locali- 

 ties. He knew it was common in Delaware, Maryland, and Texas. 

 He had regarded arsenate of lead as inefficient against the rose 

 beetle, but a New Hampshire graduate had found that used at the 

 rate of 4 pounds to the barrel it would kill them. Perhaps this 

 was due to a difference in climate. 



Mr. Marlatt said that it was a common experience at these meet- 

 ings to have conflicting or opposing results from different sections 

 of the country from what is claimed to be the same treatment for 

 different insect pests, and the theory is commonly hazarded that 

 the effectiveness or ineffectiveness in different localities of standard 

 insecticides or methods of control is due to climatic differences. 

 While there might be occasionally some basis for this belief, the 

 theory did not appeal very strongly to him, and he thought it was 

 being rather overworked. He believed that if a poison or other 

 insecticide killed an insect in one locality it was very apt to accom- 

 plish the same result in another if applied in essentially the same 

 way. The only climatic variations which were likely to affect the 

 insecticide action are conditions of moisture or rainfall which would 

 remove the insecticide before it had time to have its full effect; 

 but certainly food poisons and contact insecticides, unless so influ- 

 enced, should have the same results on ordinary insects within the 

 range of the latter, and he believed that most of the differences 

 alleged were to be explained on variations in the poison or methods 

 of application rather than climate. 



