The diseases and pests of the rubber tree . effect observable to the casual observeris the death, now and again, of one of the thinner topmostbranches. It is to be noted, however, that if the course ofthe disease is slow it is in consequence more to be feared,as a large number of trees may be attacked before anythingserious is noticed. Sharpies states : This root disease is common on mostof the older plantationsin the Federated MalayStates, though its presenceis unsuspected. The fungusworks slowly and insidi-ously, the crown of leavesbecoming thin as it pro-gresses in the collar. Thediseased t
The diseases and pests of the rubber tree . effect observable to the casual observeris the death, now and again, of one of the thinner topmostbranches. It is to be noted, however, that if the course ofthe disease is slow it is in consequence more to be feared,as a large number of trees may be attacked before anythingserious is noticed. Sharpies states : This root disease is common on mostof the older plantationsin the Federated MalayStates, though its presenceis unsuspected. The fungusworks slowly and insidi-ously, the crown of leavesbecoming thin as it pro-gresses in the collar. Thediseased tissue is usuallyconfined to one side of thecoUar, and from this sidelatex cannot be opposite side may givea good yield, and tappingis continued till the amountof latex obtained begins todiminish. When this stageis reached the tree soon diesand is taken out. The affected wood atthe base of the stem ispermeated with conspicu-ous black lines (Fig. 4).These run irregularly upand down the stem, or transversely. The wood is divided. FiQ. 4.—Ustulina zonata; black lines inwood. X J. THE RUBBER TREE CHAP, 58 up by thin sheets of black tissue, and the edges of thesesheets appear as lines when cut. Sometimes these sheetsform closed pockets, and in section appear as irregular ovals or circles surroundingdark - coloured patches ofdiseased wood. Betweenthe black lines the wood issometimes uniformly brown(Fig. 5). Emphasis is laid, inthe Federated Malay States,on the fact that the diseasedwood is dry and tindery, liketouchwood, and hence thedisease has been named DryRoot and Collar Rot. Typical characteristics ofthe disease on the roots arebest seen by examining thelaterals. There is no externalmyceliujn, such as is foimdin Fomes lignosus or BrownRoot disease. The roots(Fig. 6) frequently bear smallblack nodules, two or threemillimetres in diameter, whichare white internally and mayappear white on the top if they have been damaged whenthe root was dug up. They are usually scat
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