Seedling survival, post-harvest recovery and growth rates of the woodrose-producing mistletoe Erianthemum dregei (Loranthaceae) on Sclerocarya birrea

The mistletoe Erianthemum dregei (Eckl. & Zeyh.) V. Tieghem produces a woodrose type haustoriurn on host trees. In some rural areas of southern Africa woodroses are harvested for their unique ornateness and prepared for sale as curios. Concern for the sustainability of mistletoe populations led to this study. Sclerocarya birrea (A. Rich.) Hochst hosts were artificially inoculated with hand-excised mistletoe seeds and post-harvest recovery of mistletoes on 12S. birrea trees were investigated a year after disinfection. E. dregei exhibited 25% germination after 5days but no seedlings survived a month in the field. Seventy-eight living E. dregei removed in 1994 were replaced one year later by 68 ‘new’ plants probably through resprouting from internal, longitudinal cortical strands which allow for rapid vegetative recovery after removal. Poor seedling establishment and the occurrence of new recruits on branches between 0.0002 to 0.025m2 cross-sectional area could indicate resprouting rather than recruitment from seed. The growth rates of 22 E dregei woodroses growing on S. birrea were assessed over a 12month period during 1994/5. These woodroses varied in size from seedlings to individuals with a diameter of 25cm. Absolute growth rate increased linearly with woodrose size, with most growth occurring during the first 6months (August–February) relative to the second (February–August). Relative growth rates declined (negative In function) from very high rates for very small woodroses to fairly similar slow rates of growth for all other sizes. Woodroses of diameter 10cm and 25cm are typical size classes sold as curios. Using the growth data, it is estimated that woodroses of these sizes are 40±25 (S.D.) and 56±35years old respectively. These slow rates of growth must be taken into consideration when determining sustainable harvesting limits