ANOTHER GALL OF THE ELM 



267 



The galls become dark with age. To a certain extent, these 

 galls interfere with the 'proper functioning of the leaves and are 

 unsightly. Nevertheless, the insects are not regarded as serious 

 pests. 



Control. The only practical remedy is to cut off galls when 



FIG. 268. Gall on red elm made by a plant louse, Pemphigus ulmi fusus. 



FIG. 269. Basswood leaf and fruit showing galls made by a two-winged fly. 



noticed on young trees and to burn them while still containing the 

 lice. 



Another gall of the elm is that made by a plant-louse (Pem- 

 phigus ulmi fusus Walsh) (Fig. 268). Basswoods also suffer from 

 the attacks of gall-making insects (Fig. 269). 



