130 BOAliD OF AGRICULTUKE. [Pub. Doc. 



large numbers to feed upon it. In some cases when the psylla 

 is particularly abundant such quantities of honey dew are pro- 

 duced that it falls like a fine rain, and in any case when it dries 

 it forms an ideal place in which a black, sooty fungus may 

 grow, and this gradually turns such places black, and gives 

 the leaves and twigs the appearance of having been covered 

 with soot. This fungus does not itself attack the tree, but 

 where it is present it and the honey dew close up many of the 

 openings through which the tree obtains its air, and thus in- 

 directly affect its health. 



The young psyllas suck the juices from the tree, and molt 

 several times during their growth as their skins become too 

 small, and after about a month at one of these molts the adult 

 insect is produced. Egg laying for another brood now follows, 

 and the eggs hatch in eight or ten days, because of the warmer 

 weather which has now arrived. About a month later the 

 adults of this brood appear, and we may have as many as four 

 broods in Massachusetts before winter puts a stop to this 

 process. 



The effect of the feeding of these little pests upon the tree 

 is to a large degree dependent upon their abundance. In gen- 

 eral, trees attacked fail to make much new growth, but remain 

 at a standstill. The quantity of fruit produced and its size 

 are also determined to some extent in this way, while in severe 

 cases the leaves turn yellow, the fruit drops from the trees when 

 partly grown, and many of the buds die. In one case, where 

 a pear orchard in the spring promised a yield of about twelve 

 hundred barrels, the actual yield was less than a hundred. 



Numerous methods for the control of this insect have been 

 tested, but only one has given satisfaction, and this is kero- 

 sene emulsion. About the 15th or 20th of May, or as soon as 

 the leaves are well expanded and the young have begun their 

 work, one part of kerosene emulsion diluted with twenty-five 

 parts of water, applied with a nozzle which will give a fine mist, 

 has proved very effective against all the young psyllas it reaches; 

 and when a thorough application has been made at this time, 

 the later broods are so small that they may safely be neglected. 

 Where this treatment can be given soon after a heavy rain, 

 the results are better than is otherwise the case, the rain wash- 



