Investigation on agrilus nubeculosus (fairm) with special refernce to its association with gummosis in acacia senegal
2006
Khalil, S.A.A., National Forestry Corporation (Sudan)
This study was carried out in El Heimayra forest (Northern Kordofan State) to investigate farmers believe that there is a positive correlation between the abundance of A. nubeculosus and the yield of gum arabic from A. senegal. Trees from three age classes namely; 5-9, 10-14 and 15-20 years old were selected randomly. Twenty trees were covered with wire mesh and sprayed with 57% malathion and labeled as control trees (C) and 20 other trees were left for natural infestation by the insect and labeled as infested trees (O). These experiments were replicated during three tapping periods: early, mid and late. Yield from infested trees increased by 97% in all age classes and tapping periods. Yield from infested trees was highest in early period in all age classes. Yield from infested trees varied considerably in its physical properties (colour, shape, optical rotation, moisture content and size) as well as chemical properties (nitrogen, ferrous, calcium and manganese contents) as compared to gum from control trees. The life cycle of A. nubeculosus was investigated. Micro-organisms in the hindgut of A. nubeculosus were isolated and identified as Aspergillus spp.and Staphyllococus spp. Trees which were inoculated with fungus produced higher amounts of gum than those which were inoculated with fungus and bacterium simultaneously, with bacterium alone, and higher than trees which were naturally infested with A. nubeculosus and control trees. It is apparent that A. nubeculosus transmits both Aspergillus spp.and Staphylococcus spp.which might have presented a stress that resulted in more gum production confirming earlier hypothesis that gummosis is a pathological reaction and/or a modification of some physiological processes of A. senegal as a result of microbial infection
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