The Peak Tree Psylla. 247 



As soon as the eggs of the Mbernating form were found, 

 experiments were begun with a view to the destruction of the 

 insect in this stage. As the eggs were so freely exposed on the bare 

 twigs to the action of any fluid, it was confidently expected that 

 the pest could easily be checked here. Both field and laboratory 

 experiments were conducted. The branches containing the eggs 

 were dipped into the solution in each case, thus making sure that 

 the treatment was thorough. The results obtained were very 

 surprising. Eggs dipped in the following substances hatched a 

 few days afterward: 



Kerosene emulsion (Hubbard-Riley fonnula) used full istrength; 

 and diluted with thi-ee pai-ts of water heated to 130 degrees F. 



Kerosene undiluted. 



Turi)entine emulsion diluted with three pai-ts of water. 



Tui'pentine undiluted. 



Crude carbf)lic acid emulsion diluted with ten parts of water. 



Eesin wash used triple strength, and heated to 130 degrees F. 



WTiale-oil soap and sidphide of potash ^^ash used double 

 strength. These last two washas are successfully used in com- 

 bating all stages of scale insects. 



Concentrated potash, one pound to one gallon of water. 



Benzine undiluted.* 



Mo«it of the above substances injured the buds; concentrated 

 potash an.d carbolic acid when u.sed in less dilutions kUled the 

 buds. These results made it evident that it was impracticable to 

 fight the pest with insecticides while in the egg state. 



However, if the pear growers could wait until about April fif- 

 teenth before pruning theii' trees, they could destroy many eggs. 

 Most of the eggs are laid by that date near the tips of the last 



» 



* Similar results were obtained by E. S. Goff of Wisconsin while experiment- 

 ing upon the eggs of Aphids. He found the shell extremely resistant, scarcely 

 yielding to the strongest acids and alkalies. (Insect Life, iv, p. 327.) 



There seems to be no other records of any careful experiments with the differ- 

 ent insecticides upon the eggs of Aphids or of the allied Psyllids. Kerosene 

 emulsion is often recommended, and the eggs of some species of Aphids may, 

 possibly, be thus destroyed. There is need, however, of more obserrations upon 

 the penetrating and killing power of insecticides upon the eggs, not only of 

 Aphids but of other insects. 



