Ninth IiEport of the State Entomologist 329 



Remedies. 

 Recent writers upon this insect have been recommending as perhaps 

 the best method for its destruction, that of killing the eggs in which 

 the insect was believed to hibernate during the winter, by spraying 

 them with kerosene emulsion. This was based, not on actual experi- 

 ment, but on the known insecticidal property of kerosene and its pene- 

 trative powers. Late experiments, however, carefully made, have 

 given the unlooked-for result that there are insect eggs which can not 

 be killed by kerosene emulsion of the extreme strength with which it 

 may safely be used on vegetation, or even by undiluted kerosene. 

 Such are the eggs of the Psylla, as has been shown by Mr. Slin- 

 gerland in his Bulletin on the Pear-tree Psylla previously quoted. It 

 was found by him that eggs dipped in a kerosene emulsion of full 

 strength, and into kerosene undiluted, hatched a few days thereafter. 

 The same result attended their immersion in spirits of turpentine, carbolic 

 acid emulsion, whale-oil soap solution, strong potash solution, and undi- 

 luted benzine. 



The vulnerable stage in this insect is when it has hatched from the 

 ^gg and the larv?e are distributed over the young leaves and on the 

 leaf stalks. This, in ordinary seasons, in the State of New York, would 

 be about the middle of May. If the infested trees are at this time 

 spraj'-ed with kerosene emulsion, even so weak as five per cent of 

 kerosene, it will be fatal to all the insects with which it comes in con- 

 tact. With careful spra3dng very few should fail of being reached, 

 unless they are protected by a covering of honey-dew. 



When the insect has passed to its winged stage, it has attained com- 

 parative immunity in the alertness with which it takes wing and leaves 

 the tree upon the first motion communicated to the foliage by the 

 impact of the spraying liquid. But even so late as the month of Sep- 

 tember, the war against the insect should not be abandoned, for multi- 

 tudes may be destroyed, and the hibernating individuals for the 

 following year greatly reduced. The kerosene emulsion will still be 

 effective, but in its application, all of the ordinary spraying-nozzles 

 should be discarded, even the finest gauge of the Nixon nozzle, and a 

 Vermorel used, adjusted to the delivery of the finest possible mist-like 

 spray. With proper care the emulsion may be distributed over the 

 entire foliage without scarce stirring a leaf and with the least possible 

 alarm to the winged tenants. Of those that take wing — after circling 

 about the tree for a while — on their return to the leaves, their bodies 

 will in most cases come in contact witli the liquid, and take up sufficient 

 of it to cause their death. 

 1893 42 



