A rust epidemic of the coffee shade tree (Paraserianthes falcataria) in East Timor

摘要

During the past two years a very damaging disease has affected Paraserianthes falcataria (formerly Albizia falcataria), the tree most commonly grown in East Timor to provide shade for coffee plantations. A taskforce established by the Department of Agriculture and Forestry of East Timor in 2001 found that 67% of the total coffee plantations, across all eight districts where the crop is grown, were affected. The district of Ermera, which accounts for more than half of the total coffee-producing area of the country, was one of the most severely affected regions. The disease is caused by Uromycladium tepperianum, a rust disease known to affect only acacias and Paraserianthes/Albizia spp., resulting in the formation of galls on foliage and branches. So far it appears that the strain of the fungus causing damage is restricted to Paraserianthes. The pathogen attacks all above-ground parts of susceptible hosts, however damage is most severe when shoots and branches are affected, as these are girdled by the rust and secondary invading insects and saprophytes which invade galls. As shoots are partially girdled and come under severe stress, massive defoliation of the tree crowns occurs and, eventually, large trees can be killed. The loss of shade is expected to result in significant reduction in coffee yield and is promoting weed invasion on an unacceptable scale. Shade-tree crown components and, eventually, whole trees are dying and falling branches and wind-thrown trees will damage the coffee. Falling branches will create very dangerous conditions within the plantations and along sections of highways, which are overhung by heavy limbs. No practicable remedial measures can be recommended to restore the health of standing trees. The likely solution will be to remove severely affected shade trees from plantations, replant with alternative shade species or rust resistant selections of P. falcataria and probably replant the coffee. Expert opinion quoted in a recent survey of the coffee sector in East Timor has indicated that virtually all the coffee plantations in East Timor would benefit from replanting. In the longer term, therefore, some positive benefits will flow to the farmers and the industry by the provision of an opportunity to replace coffee plantations with improved cultivars.