Most of the major diseases of Hevea brasiliensis are of worldwide distribution (with the notable exception of South American leaf blight, against which strict quarantine regulations are enforced by rubbergrowing countries outside the Americas to prevent t h e unauthorised import of Hevea) but their local severity and importance vary from one region t o another. Root diseases are a serious problem nearly everywhere and regular rounds of inspection and treatment are essential while the trees are still young in order t o prevent serious losses. The recently introduced prophylactic collar protectant dressings specific to each of t h e three main diseases are valuable aids to control.Diseases of the tapping panel may prevent tapping or hinder bark regeneration; black stripe in particular (Phyrophrhora palmivora) can be very persistent and is often eradicated only by repeated therapeutic fungicidal treatment of t h e bark. Stern diseases, chiefly pink disease (Corricium salmonicolor), are important in certain areas in wet weather, and can lead to severe damage and even dieback in t h e absence of effective treatmen t.Four major leaf diseases can have a debilitating effect on the tree. Abnormal leaf fall (Phytophrhora spp.) is severe in India, causing the abscission of mature leaves during the monsoon rains; treatment necessitates t h e application of a pre-monsoon prophylactic copper spray. Secondary leaf fall, caused both by Oidium heveae and Collerorrichum gloeosporioides which infect the flushes of new leaves produced after the annual leaf change (wintering), varies greatly in severity according to local weather and cultivar. It can be controlled by repeated rounds of an appropriate prophylactic fungicide or, under certain conditions, by artificially hastening the onset of wintering (and thus of refoliation) by removing the old leaves with a contact herbicide. By far the most important leaf disease is South American leaf blight (Microcyclus ulei); it is largely responsible for the lack of a vigorous rubber industry in South America, the home of the rubber tree. It can only be effectively countered by t h e use of resistant cultivars.The economic importance of the above diseases is discussed and current control measures described. PANS 21: 268-288,1975.
