PEAR GNAT MIDGE. 91 



roots not too near the surface, the plan of skimming the surface, and 

 destroying the surface earth with its contained infestation would 

 answer well. The depths given for presence of the cocoons are half an 

 inch to two inches, and this might (I believe) often be safely removed. 

 Any time would be suitable for this operation between the time of the 

 falling of the infested Pears from the trees and such a date in the 

 following winter or spring as would ensure that the cocoons should be 

 skimmed off and destroyed in the infested earth before the season came 

 for the development of the insect contents. The Gnat Midges appear 

 with the Pear blossoms, but it would be well to be some weeks before- 

 hand, and also to be sure that the earth is burnt, or in some way 

 thoroughly got rid of with its contents. 



"Where Pears are grown in grass orchards it might be hoped that 

 a deal of the infested fallen fruit would be cleared off by having sheep 

 or pigs on the land to eat it as it falls. 



The best remedy of which we have information at present appears 

 to be (as reported by Prof. J. B. Smith) application of kainite to 

 infested ground. In an observation on infested Pear orchard land in 

 New Brunswick, U.S.A., a heavy top-dressing of kainite was applied 

 in late summer, and under the infested trees it was applied at the rate 

 of over half a ton per acre. The result was that in the following year 

 scarcely any of the fruit was found to be infested ; whilst in another 

 orchard close adjoining, in which the ground had not been treated, on 

 close examination it was found that of one kind especially grown 

 fifty per cent, were "midged," and of the other kind named not one 

 could be found to have escaped. 



In laboratory experiment Prof. Smith found that where nitrate of 

 soda was sprinkled in quantity that would represent a fair top-dressing 

 in ordinary field use, on sand in which maggots had gone down, that 

 not ten per cent, of the larvas were alive (so far as examined) in their 

 cocoons ; and where a double quantity of the nitrate was applied, a 

 still lesser proportion of the maggots were found to be alive. 



Muriate of potash in about the same quantities showed results of 

 respectively nearly one-half or three-quarters of the maggots dead in 

 their cocoons. 



But in the case of sprinkling with a small quantity of kainite, only 

 three per cent, of living larv« were found in the cocoons examined ; 

 and where double quantity was used, "not one-third of the larvae in 

 the jar had ever formed cocoons, and those that did seemed all of them 

 to be dead." — (J. B. S.) The experiment is given in minute detail in 

 the Bulletin referred to below,* the period from commencement to 



* See, for much useful information on this attack, " The Pear Midge {Diplosis 

 pyrivora, Eiley)," Bulletin 99 of New Jersey Agricultural College Experimental 

 Station, April 4th, 1894. 



