Abstract
‘Leptocybe invasa’ Fisher & La Salle (Hymenoptera: Eulophidae) has been recorded in many tropical and sub-tropical regions of the world as a gall wasp attacking ‘Eucalyptus’ species. It completes much of its life cycle inside Eucalyptus tissue thus hampering chemical control. These investigations were done to gather ecological information needed to make ‘L. invasa’ amenable within eucalyptus agroecosystems: (1) cues for ‘L. invasa’ oviposition in relation to olfaction and visual stimuli; (2) foraging and patch use by adult ‘L. invasa’; (3) plant host condition in relation to successful attack by ‘L. invasa’; and (4) variability of ‘L. invasa’ attack between major Eucalyptus species. Caged, infested ‘E. saligna’ seedlings were used as sources of ‘L. invasa’ while caged healthy seedlings were used in‘ L. invasa’ ecological experiments with mean gall numbers per seedling as response variables. More eggs were laid by ‘L. invasa’ in response to oviposition cues in relation to olfaction stimuli than visual stimuli (p < 0.05) and patch residence time was greater than time spent in foraging from patch to patch (p < 0.05). Low nitrogen fertilization and moderate watering regime lowered the severity of attack by the pest (2.6 ± 0.9 galls per seedlings; p < 0.05). ‘E. saligna’ was the most susceptible species to ‘L. invasa’ attack (15.43± 0.29 galls per seedling) compared to ‘E. globulus’ and ‘E. citriodora’, having only 0.86±0.07 and 0.94±0.07 galls per seedling respectively. The variability in ‘L. invasa’ attack between the major Eucalyptus species was significant (p < 0.05). Use of resistant Eucalyptus species like, ‘E. camaldulensis’; having polycultures; and low application of N-fertilizers and moderate watering regimes have been recommended as cultural control strategies against ‘L. invasa’ gall wasp.
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Reference
Odhiambo, K.O., Wanjala, F.M.E. and Khaemba, B.N. (2013). Ecological Dynamics and Cultural Control of Eucalyptus Gall Wasp, Leptocybe invasa Fisher & La Salle. African Journal of Education, Science and Technology, 1(2):75-83