The diseases and pests of the rubber tree . rarein old Eubberplanted on low-lying land in Mal-aya, having beenfound iri NorthernPerak, in the dis-trict round TelukAnson, and in thecoast lands ofSelangor. Only afew trees on un-dulating land wereseen to be at-tacked by it. The myceliumof the fungus atonce distinguishesthis disease fromthose caused byFomes lignosusand Fomes lamao-ensis, but it is not immediately evident like that of thetwo latter species. When the root isdug up the cortex is found to bedecayed, but there is no externalmycelium. But if the cortex is re-moved, black or red flattene
The diseases and pests of the rubber tree . rarein old Eubberplanted on low-lying land in Mal-aya, having beenfound iri NorthernPerak, in the dis-trict round TelukAnson, and in thecoast lands ofSelangor. Only afew trees on un-dulating land wereseen to be at-tacked by it. The myceliumof the fungus atonce distinguishesthis disease fromthose caused byFomes lignosusand Fomes lamao-ensis, but it is not immediately evident like that of thetwo latter species. When the root isdug up the cortex is found to bedecayed, but there is no externalmycelium. But if the cortex is re-moved, black or red flattened strandsare seen running over the surface ofthe wood (Fig. 10). The inside of thecortex and the outer layers of thewood are usually a deep blue, or purple,when fresh, and have a particularlyfoul smell. The blue colour, however,is not confined to roots attacked bythis disease, but sometimes occurs on tap roots killed byUstuKna, below the level at which the UstuUna has attackedthem. The smell, too, is not a distinctive sign of this disease,. Fig. 10.—SphaerosHlbe repens;mycelium on wood of root. 66 THE RUBBER TREE chap and is probably caused, not by the SpTiaerostilbe, but by theaction of secojidary organisms on the cortex or wood. The mycelial strands are usually about two millimetresbroad, but they may reach a breadth of five millimetres. Atfirst they are red externally and white internally, but whenthe root is much decayed the strands decay also and becomeblack. If the fungus is living the strands are fairly thickand stand out prominently above the wood, but on olddecayed roots they are little more than a black film on itssurface. When the cortex is stripped off the wood thestrands are often split lengthwise, especially when they arein a living condition, and half remains on the cortex and halfon the wood. The white inner tissues of the fungus are thenexposed, and these often present a fern-like strands are not simple cords composed of hyphae lyingside by
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