26 



FOREST ENTOMOLOGY. 



witches'-brooms artificially, thus proving that these malformations 

 really originated from the mycelium of Exoasciis."'^ 



As the cause of the " witches'-broom " is ascribed both to mites and 

 fungi, it is suggestive of the advantages and pleasures of original 

 microscopical investigation. Still, these abnormal growths might 

 have accrued from excessive development of adventitious buds, caused 

 by the constant irritation of the Eriophyinse without the presence of 

 Exoascus. 



I have found this species in several parts of Xorthumberland. 



Eriophyes psilaspis (Nal.) 

 Phytoptiis taxi (Murray). 



This species (fig. 25) was first discovered by Professor Sir Thiselton 

 Dyer in the spring of 1875 doing immense damage to young hedges, 



which damage had hither- 

 \t-t / ^^ to been ascribed to frost. 



I found it plentiful on 

 the under side of the 

 lower branches of a 

 yew-tree at High Legh, 

 Cheshire, from which the 

 photographic illustration 

 was taken. I have often 

 found it very injurious to 

 young yew-trees in the 

 nursery - lines, and also 

 occasionally on yew 

 hedges. 



As this species is cer- 

 tainly injurious, it is 

 well to have recourse to 

 some remedial measures. 

 In the case of hedges, 

 where regular trimming 

 is resorted to, it would be well to burn all prunings ; and as regards the 

 young yew-trees in nursery-lines, it would be best to hand-pick or cut 

 off the infested buds, say about the latter end of May, and burn them. 



^ Tubeuf, Diseases of Plants induced by Crj'ptogamic Parasites. English 

 edition, by M\ G. Smith. 1897. 



Fig. 25. 



-Abortive swollen bitds caused by Eriophyes 

 psilaspis on English yew. 



