The diseases and pests of the rubber tree . patch on the other viewed from the ground thebranch appears to have been givena very thin coat of whitewash, butwhen it is cut down and examined,all the minute scales of the outerbark are clearly distinct, and thereis no general covering of distinguishes it from earlystages of Pink Disease, in whichthe bark is usually covered withfine silky threads. On careful examination, however, a white thread will often be found Fig. stem Blight, x J. running ovcr the whitened patch. This is most easily seen on thewhite lateral s
The diseases and pests of the rubber tree . patch on the other viewed from the ground thebranch appears to have been givena very thin coat of whitewash, butwhen it is cut down and examined,all the minute scales of the outerbark are clearly distinct, and thereis no general covering of distinguishes it from earlystages of Pink Disease, in whichthe bark is usually covered withfine silky threads. On careful examination, however, a white thread will often be found Fig. stem Blight, x J. running ovcr the whitened patch. This is most easily seen on thewhite lateral streaks, where it is usually situated down themiddle. On the large patch it is not so easy to make out, andthere it is frequently interrupted, after running for alength of a few inches it disappears, and reappears againhigher up. The thread is white, usually smooth, and aboutthe thickness of cotton at most: it is thinner than the averageThread Blight. At the upper margin of the white patchthere is often a fringe of fine, white V STEM DISEASES 159 In the commoner Thread Blights, the superficial myceliumon the stem usually occupies a very narrow line, being limitedto the visible thread and a very short distance on either White Stem Blight, however, the thread gives off hyphaewhich run over the stem, usually between the small barkscales, and these give ofE still finer hyphae which penetratethe scales. All these hyphae are invisible to the naked eye,but they loosen the bark scales, and consequently make thestem appear white. The white colour is due to the action ofthe fungus on the scales ; it is not the colour of a covering ofmycelium. When the affected stem dries, the minute scalesdrop ofi like bran. The fungus also occurs on Tea, and on that it whitensthe branches completely, and travels to the leaves, which itattacks and kills rapidly. It has not yet been found on theleaves of Hevea, or on branches less than an inch in greater development on Te
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