.•■^pril, '21] parrott: dusts for sucking insects 207 



his orchard operations who fails to make provisions for the control of 

 these pests. Likewise, the neglect of pear psylla, thrips, or the green bug 

 is likely to be attended with serious consequences as is usually mani- 

 fested by the reduced yields and impaired vitality of the trees. Similar 

 considerations hold true for the grape leafhopper, the currant aphis and 

 four-lined plant-bug, the potato aphis and leafhopper, and the onion 

 thrips. In view of the importance of this class of insects and of the need 

 for information as to their susceptibility to dusting preparations, the 

 Geneva Station began a serious investigation of the problems during the 

 past season. My contribution to this symposium, therefore, deals 

 largely with the more important results of this inquiry. 



Tests with Various Fruit Insects 



A series of experiments are here described which were designed to 

 ascertain the effectiveness of dusting mixtures on a nimiber of common 

 sucking insects. The objects which we hope to attain, and which we 

 succeeded in attaining in part, were: (1), Data on the susceptibility 

 of various insects to dusting preparations with definite ratios of nicotine; 

 (2) , some knowledge of the efficiency of dusting for the control of certain 

 species under field conditions ; and (3) , information as to the importance 

 of accessory factors in the effectiveness of dusting operations. 



Conditions of the Tests 



The following species of insects were used in the experiments: The 

 green apple aphis {A. pomi De Geer), the rosy aphis {A. sorbiY.a\t.), 

 the grain aphis {A. avencB Fab.), the apple leafhoppers {E. roscB L. and 

 E. unicolor Gillette), the apple redbug {Lygidea mendax Reuter), the 

 pear psylla (Psylla pyricola Forster), the currant aphis {Myzus ribis L.), 

 the four-lined leaf-bug (Poecilocapsus lineatus Fab.), and the potato 

 aphis {M. solaniJoUi Ash.) The dusting preparations were applied with 

 "hand dusters," "hand blowers," or orchard power outfits. A mixture 

 of superfine sulfur, 90 percent, and powdered lead arsenate, 10 percent. 

 was the carrier of the nicotine. In many of the experiments provision 

 was also made for application of liquid insecticides at standard strengths. 



Susceptibility of Insects to Dusting Preiarations 



The Apple Redbug 



Experiments with apple redbugs were conducted on June 1 and 2 in an 



18-year-old orchard composed chiefly of such varieties as Greening, 



Hubbardston and Baldwin. This planting had suffered serious injuries 



for successive years, and at the time of the test over 90 percent, of the 



