SCRAPING TREES. 



191 



Frenchman, M. Robert, as described in the Gardener's 

 Chronicle " and referred to by Miss Ormerod. He gives the 

 quotation from Miss Ormerod as follows : — 



The best remedy appears to be that adopted with great success 

 in France by M. Robert, after careful observation of the circum- 

 stances which stopped the operations of the female beetle when 

 gnawing her gallery for egg laying, or which disagreed with or 

 destroyed the maggots, and is based in part on similar observa- 

 tions of the effect of flow of sap to those noticed in England by 

 Dr. Chapman. 



It appeared on examination that the grubs died if they were not 

 well protected from the drying action of the air ; on the other 

 hand, if there was a very large amount of sap in the vegetable 

 tissues that they fed on, this also killed them ; and it was observed 

 that when the female was boring through the bark if a flow of sap 

 took place she abandoned the spot and went elsewhere. It was 

 also noticed that the attack (that is, the boring of the galleries 

 which separates much of the bark from the wood) is usually under 

 thick old bark, such as that of old elm trunks, rather than under 

 the thinner bark of the branches. Working on these observations, 

 M. Robert had strips of about two inches wide cut out of the bark 

 from the large boughs down the trunk to the ground, and it was 

 found that where the young bark pressed forward to heal the 

 wound and a vigorous flow of sap took place many of the maggots 

 near it were killed, the bark which had not been entirely under- 

 mined was consolidated and the health of the tree was improved. 



Working on from this, M. Robert tried the more extended 

 treatment of paring off the outer bark, a practice much used in 

 Normandy and sometimes in England for restoring vigor of grow^th 

 to bark-bound apple trees, and noted by Andrew Knight as giving 

 a great stimulus to vegetation. M. Robert had the whole of the 

 rough outer bark removed from the elm (this may be done con- 

 veniently by a scraping knife shaped like a spoke shave) . This 

 operation caused a great flow of sap in the inner lining of the bark 

 (the liber) ^ and the grubs of the Scolytus beetle were found in 

 almost all cases to perish shortly after. Whether this occurred 

 from the altered sap disagreeing with them, or from the greater 

 amount of moisture around them, or from the maggots being more 

 exposed to atmospheric changes, or any other cause, was not 

 ascertained, but the trees that were experimented on were cleared 

 of the maggots. The treatment was applied on a large scale, and 

 the barked trees were found, after examination by the commis- 

 sioners of the institute at two different periods, to be in more 



