Survival, growth and gall formation by Phytolyma lata on Milicia excelsa established in mixed-species tropical plantations in Ghana.
1999
Nichols, D. J. | Ofori, D. A. | Wagner, M. R. | Bosu, P. | Cobbinah, J. R.
Milicia excelsa (Moraceae) is an important timber tree in much of Africa and when grown in monocultural plantations has been subject to nearly complete destruction by gall-forming psyllids, Phytolyma lata, when used in monocultural plantations. The impact on susceptibility to Phytolyma spp. of planting Milicia excelsa in various densities and species mixtures was tested in Ghana. Replicated plantings consisting of 11, 25, 50 and 100% Milicia in mixtures with Terminalia superba (Combretaceae) were established at a site surrounded by natural forest and in an agricultural area. In addition at the agricultural site, 50-50 mixtures of Milicia excelsa with Albizia adianthifolia (Mimosaceae), Tectona grandis (Verbenaceae), Khaya ivorensis. (Meliaceae), Ceiba pentandra (Bombacaceae) and a mixture combining all species were planted. Two months after planting, gall numbers were significantly lower in the 11% Milicia mixtures at the forest site. Gall numbers were also significantly lower at the forest site than at the agricultural site, for all densities of Milicia. At 6 months, dieback of Milicia resulting from gall formation had taken place equally on all seedlings, but survival of seedlings at the forest site was 40% higher than at the agricultural site.
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