Mukwa dieback in the state forests of western Zimbabwe
1993
Campbell, B. M | Van Wyk, M | Calvert, G. M. | Piearce, G. D.
A recent study on dieback of mukwa (Pterocarpus angolensis), in 40 stands around western Zimbabwe, is reported. In each stand, all individuals were measured and rated for crown and stem health, and samples were taken for pathological investigation. Over 60% of the intennediate size-class trees had poor health and were most noticeably affected by fire and damage from large animals. Characteristic symptoms of wilt disease were found in most sampled trees having poor crowns, and Fusarium oxysporum was isolated from streaked xylem material. Correlations, or lack of them, between various factors that could contribute to poor health of mukwa - geographical distribution, climatic variables, animal damage, fire, drought, frost, Loranthus infection, and the wilt disease are illustrated. Other environmental factors are regarded as predisposing or inciting influences, with the wilt disease being a major cause of stand-level dieback. Population projections indicate that the numbers of larger trees will decline substantially in the next 50 years, even if drastic reductions of mortality levels are achieved through intensified forest and fire-management.
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