The diseases and pests of the rubber tree . on after exposure. Once it has been seen, it is notpossible to confuse it with the red coloration of renewingbark ; it is always a muddy colour, quite different fromthe clear, translucent red of the latter, and it is clearly markedoff by a black line from the surrounding healthy bark. The disease begins from the exterior of the cortex andworks inwards towards the cambium, spreading out at thesame time more or less equally in all directions. It does not,as a rule, run in narrow bands or stripes (Fig. 12). In manycases it is detected before it has pene
The diseases and pests of the rubber tree . on after exposure. Once it has been seen, it is notpossible to confuse it with the red coloration of renewingbark ; it is always a muddy colour, quite different fromthe clear, translucent red of the latter, and it is clearly markedoff by a black line from the surrounding healthy bark. The disease begins from the exterior of the cortex andworks inwards towards the cambium, spreading out at thesame time more or less equally in all directions. It does not,as a rule, run in narrow bands or stripes (Fig. 12). In manycases it is detected before it has penetrated right through thecortex, but if left alone it kiUs the cortex down to the cam-bium and spreads laterally, as long as conditions are favour-able. It may thus extend over large areas of bark, andultimately kill the tree, without producing any open woundor giving any outward indication except the bleeding alreadymentioned. When dry weather sets in, however, the diseasegenerally stops, and the affected cortex then dries up and Plate CLARET-COLOURED CANKERPatch exposed by shaving PHYTOPHTHORA DISEASES 113 forms a scale whicli ultimately falls ofE. In these cases of self healing, the resulting damage depends entirely on theextent to which the disease has spread. If it has not pene-trated completely through the cortex a scale is formed, of a
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Keywords: ., bookcentury1900, bookdecade1920, bookidcu3192400285, bookyear1921
