Two New Shade-Tree Pests. 57 



or more broods of its very near relative, the alder sawfly miner, discussed on 

 page 58, which continues to work in the alder leaves from May until October. 



Remedial suggestions. — The suggestions given on page 62 for con- 

 troling the closely allied alder sawfly will also apply to this elm sawfly miner. 



Last autumn a treatment that doubtless materially reduced the numbers 

 of these sawflies was unwittingly applied to some of the worst infested elm trees 

 on the Cornell Campus. In grading, several inches of new soil was spread over 

 the ground beneath the infested trees. Apparently many of the little sawflies 

 failed to emerge through this layer of soil in the spring. As practically all of 

 the sawflies transform within an inch of the surface immediately beneath the 

 infested trees, it would be practicable in some cases to apply a layer of soil 

 several inches thick under the trees in autumn and remove it about June ist, 

 or after the time for emergence of the sawflies. Whenever practicable, how- 

 ever, I would advise the removal or spading under and packing down of the 

 sod from beneath the trees as described on page 62 , for I think this method is 

 more effectual. 



Last spring other peculiar conditions occurred in the clump of badly 

 infested European elms on the University Campus. It was the fruiting season 

 for several of the trees and they bloomed and fruited profusely. This process 

 delayed the appearance of the leaves until after most of the sawflies had 

 emerged and laid their eggs, which they were thus forced to do in the leaves 

 of the few non-fruiting trees. Had many of the worst infested branches on 

 the larger trees and the smaller crowded and stunted trees been removed early 

 in June, and their hordes of sawfly larvae left to dry up and die in the leaves, 

 the infestation could have been still further checked, but it was delayed and 

 finally never done. Whenever practicable and advisable, this pruning of infested 

 branches early in June should be done, as it will materially aid in controlling 

 the pest. As a result of the earth-mulch or earth-smothering treatment and 

 the delay in appearance of the foliage due to the fruiting of several of the 

 trees, the infestation in 1905 was concentrated on fewer trees and was not so 

 severe as during the previous year. 



