PINACEiE 363 



to the original leader. In such cases an early removal of super- 

 fluous shoots is necessary to prevent permanent injury to the 

 trees. Weakly trees, however, rarely recover from a serious in- 

 jury to the leader. In a few species the production of more than 

 one leading shoot is characteristic, and in such cases it is unneces- 

 sary to restrict the trees to a single leader. Lower branches 

 of forest-grown trees are killed from lack of hght, and they 

 usually fall naturally ; any that remain after the trees begin to 

 increase rapidly in girth, however, should be removed to prevent 

 knotty wood. Ornamental trees may be pruned when necessary 

 during summer or winter, but they do not respond so readily to 

 branch-shortening as do broad-leaved trees, and it is often better 

 to remove branches outright than to shorten them. Lower 

 branches of isolated trees must be removed gradually to prevent 

 too great an area of trunk being suddenly exposed to bright 

 sun. 



Numerous diseases due to insect or fungus agency attack 

 the pines. Some are of Uttle more than local importance and are 

 easily dealt with, but others cause widespread destruction. A 

 few of the most destructive insects are : — Hylobius abietis, Linnaeus 

 (Pine Weevil) and Hylastes ater, Payk., which destroy young 

 plants. The larvse feed on dead wood such as old stumps and 

 roots, but the mature insects feed on the bark of young trees 

 and sometimes ruin whole plantations. Correct cultural methods 

 and logs of young Scots pine wood placed about the plantations 

 as traps are the most effective means of dealing with the pest ; 

 traps must be frequently examined, the weevils being collected 

 and destroyed. The Pine Bark Beetles {Myelophilus jnniperda, 

 Linnaeus, and M. minor, Linnaeus), the Pine Longicorn Beetle 

 {Rhagium bifasciatum, Fabr.), and the Banded Pine Weevils 

 (Pissodes notatus, Fabr., and P. inni, Linnaeus), cause injury by 

 the larvae feeding on the cambium. Sickly or dying trees are 

 usually the first to be attacked. Their removal and the immedi- 

 ate burning of the bark may check the spread of the pest. The 

 bark should be removed from cut timber in places where this 

 insect is known to be. The Pine Sawfly {Lophy7-us pini, Linnaeus) 

 is sometimes destructive amongst young trees from the larvae 

 feeding on the leaves. Hand-picking and destroying the larvae 

 are the most effective means of coping with this insect, other than 

 the protection of insect-eating birds. The Resin-gall Tortrix 

 Moth {Retinia resinella, Linnaeus) and the Pine -shoot Tortrix Moth 

 {R. buoliana, Schiff), cause considerable injury to young and old 

 trees by the larvae destroying the leading shoots of trunks and 

 branches. In some cases injured leading shoots recover, but an 

 ugly curve is given to the trunk, which is very noticeable for 

 many years. Hand-picking of injured shoots and the preser- 

 vation of insect-eating birds appear to be the only means of 



