New York Agricultural Experiment Station. 447 



tions, which were applied in varying dilutions. The effects of the 

 sprays on psylla eggs are given in the accompanying table. 



Table XI. — Effect of Various Insecticides on Psylla Eggs. 



Treatment. 



Lime-sulphur 



Lime-sulphur 



Lime-sulphur 



Fish-oil soap 



Kerosene emulsion 



Miscible oil 



Black leaf extract . 



Black leaf 40 



Checks 



Dilution of spray. 



(Concentrate 1-8) . . 

 (Concentrate 1-6) . . 

 (Formula 15-20-50) 



(1-5) 



(1-8) 



(1-15) 



(1-30) 



d-40) 



(1-1000) 



Unsprayed 



Bud 



spurs 

 counted. 



90 

 75 

 102 

 100 

 100 

 100 

 100 

 100 

 100 

 100 



Eggs Counted. 



Sound. 



39 

 18 



1,806 

 232 

 900 

 800 

 824 

 920 

 810 



2,522 



Col- 

 lapsed. 



2,082 



339 



564 



20 



52 



45 



64 



48 



61 



175 



Eggs 

 killed. 



Per ct. 



98 



94 



*24 



8 



5 



5 



7. 



5 



7 



7 



* The small percentage of eggs destroyed in this test was presumably due to the 

 lower amount of sulphur in solution in the wash. 



In these tests the lime-sulphur solution was the only spray that 

 functioned in any marked degree as an ovicide. Oils and soapy 

 solutions appear not to have caused a decrease in the development 

 of the eggs. The percentage which did not hatch in these instances 

 apparently represented about the normal decrease for that season 

 due to infertility, as shown by the checks. 



DISCUSSION OF RESULTS. 



Efforts to control the psylla in pear orchards through applications 

 of contact sprays during the summer months have, on the whole, 

 proven unsatisfactory in most plantings. These failures have been 

 due chiefly to the great activity of the adults, the resistance of the 

 old nymphs, and the protection afforded to the nymphs in the more 

 advanced stages by secretions of honey-dew with which they are 

 usually surrounded. There is, moreover, an intermingling of the 

 " flies," eggs and nymphs of the summer brood which render it 

 exceedingly difficult to make much headway against the insects 

 with control measures during those months, since all of these stages 

 of this pest are not susceptible to a single spray mixture which can 

 safely be employed on foliage. 



