EFFECTS OF BRUCHID BEETLES ON GERMINATION AND ESTABLISHMENT OF ACACIA SPECIES

The effects of bruchid beetles on seed germination and seedling establishment of Acacia gerrardii and A. sieberiana were investigated experimentally. Infested and non-infested seeds from each of the Acacia species were divided into two groups. One group was set for germination trials in petri dishes fixed with moist filter papers at about 25 degrees C in the laboratory. The second group was planted in soil in wooden boxes for monitoring seedling emergence, growth and establishment. Bruchid beetles reduced significantly (P<0.05) the germination and seedling establishment of A. gerrardii, while they promoted early germination and establishment in A. sieberiana. Differences observed are possibly due to the difference in the amount of food reserves by the Acacia spp. Removal of insect predation would possibly result in establishment of many seedlings of A. gerrardii, while A. sieberiana has adapted itself to survive bruchid beetle infestation. Long-term monitoring of the relationships between bruchid beetles and the dynamics of Acacia seeds and seedlings, and the possibility of a method of biological control of Acacia spp., are recommended.