WEEDS AND FUNGI 135 



however small. Such wounds are always present on the 

 younger parts of the stem, being caused by the bites of 

 various insects, especially the larch aphis (Chermes laricis) 

 and the larch miner moth (Coleophora laricelld). Trees from 

 ten to twenty years old suffer most : It has been found on 

 Japanese larch, which is therefore not likely to be spared 

 from this scourge, though it is not much attacked at present. 

 The disease is worse in low-lying damp situations, and in 

 frosty places than on high-lying land. It is usually worse 

 in pure, densely-grown, larch woods than when the larch is 

 scattered amongst other species. Bark which is over fifteen 

 years old is usually not pierced by the fungus, so that, in a 

 larch thirty years old and 45 feet high, the bottom 20 feet 

 or so are safe, if not already cankered. 



The chief protective measures to be taken against this 

 disease are : To grow it in situations with a climate as near 

 as possible that of its natural home, the Alps ; that is on 

 north aspects, and at high elevations ; to give it plenty of 

 light and air by growing it singly, or in small groups, in 

 woods consisting of species which grow slower than itself, 

 so that its head will always be fully exposed ; it does best 

 when mixed with beech or as standards over coppice ; to 

 avoid growing it in large pure woods; to grow it only on 

 good well drained, but not dry soils ; or on stony soils with 

 plenty of humus ; to avoid pruning green branches ; and 

 finally, in the thinnings to cut out all badly diseased trees. 



The great object should be to induce vigorous growth of 

 the larch. If this is obtained the disease will not get the 

 upper hand, and the timber, even if cankered here and there, 

 will still be of considerable value. If the larch gets into 

 a bad state of health it soon gets covered with canker and 

 its value is then much reduced. The older the trees can get 

 before being attacked the longer will be the length of timber 

 free from canker. 



