LARCH DISEASE INQUIRY. 217 



to have some influence on the intensity of the disease. As 

 regards the effect of aspect, no definite conclusions are possible, 

 individual observers citing cases where the disease seems equally 

 prevalent on all aspects ; and as regards the natural drainage 

 of the soil, the evidence appears equally conflicting. There seems 

 to be a concensus of opinion, however, amongst observers, that 

 disease is more prevalent on trees growing on low-lying ground 

 than on those growing on elevated ground ; but there is much 

 difference of opinion as to whether the actual amount of moisture 

 in the soil has any marked effect on the disease. 



Regarding the age at which trees seem most liable to attack, 

 there is great diversity of opinion, ages ranging from two to thirty 

 years being given. The youngest age at which plants have 

 been observed to be attacked is given as two years, while one 

 observer states that he has seen it " in nursery lines," but without 

 giving the age of the plants. 



On one estate, several woods are reported in which no disease 

 has been observed, and from a few localities woods practically 

 free are reported ; and, of course, as was to be expected, several 

 mature crops are reported as being free. It must be said, how- 

 ever, that where the age of the trees is not given, investigation 

 seems necessary. As to whether the disease is on the increase 

 or otherwise, no definite conclusion can be arrived at from the 

 reports, there being a direct conflict of opinion on this point. 



As regards climatic agencies, frost, bending of the branches 

 by snow, and strong winds are given as the chief causes of 

 disease, while other physical agencies, such as gunshot wounds, 

 and tying of the plants in bundles, are given in a few instances only. 



Among insects, a considerable number of observers report 

 outbreak of disease after attack by Aphis and the caterpillar 

 of the larch miner moth ; and one observer records an outbreak 

 after attack by pine-weevil. Among animals other than insects, 

 horses, cattle, roe-deer, rabbits, squirrels, black game, and vermin 

 of all sorts are cited as contributing causes. 



As regards sylvicultural treatment, opinions as to whether 

 disease is more prevalent in pure than in mixed crops are 

 conflicting, but there seems to be general agreement that in pure 

 woods disease is worse where the crop is dense, although several 

 hold to the opposite opinion. The general opinion is decidedly 

 to the effect that less disease is observable in naturally-sown 

 crops than either artificially-sown or planted ones ; but as regards 



