ABSTACT
Attempts at establishing large-scale plantations of African mahoganies to ensure sustainable production have been hampered by shoot borer Hypsipyla robusta Moore (Lepidoptera: Pyralidae). Studies were undertaken to determine the relative susceptibility of two species of Khaya and two species of Entandrophragma to Hypsipyla attack in Ghana. A completely randomised block design with 4 replicates was used. Quarterly data (December, March, June and September) were collected starting one year after field planting. Tree height, diameter and crown height (tree height from ground to the first branching resulting from Hypsipyla attack) were measured. Hypsipyla damage was assessed by counting the number of shoots attacked, the number of dead shoots and number of fresh shoots with larval activity. The relative susceptibility of dead shoots and the number of Hypsipyla attacks was K. anthotheca > K. ivorensis > E. angolense > E. utile. The crown height revealed that while K. ivorensis and K. anthotheca were most preferred by Hypsipyla and started branching at a low height, they exhibited an increased crown height over time. One year after planting, K. anthotheca had a crown height of 1.5m. However, after another year, the crown height had increased to 2.1m. This observation is attributed to self-pruning. This suggests that selection of genotypes and species that are tolerant of Hypsipyla attack based on early infestation may not be appropriate. Genetic factors more completely reflecting the response of the different species and genotypes to Hypsipyla attack are likely to take a few years to manifest themselves.
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