oa African Entomology - A recently introduced sawfly, Nematus oligospilus Forster (Hymenoptera: Tenthredinidae), that defoliates willows in southern Africa



Exotic willow trees, Salix babylonica L. and S. fragilis Benth., were severely defoliated in the Highveld Region of South Africa and in Lesotho during the summer of 1993/94 by larvae of the Holarctic tenthredinid sawfly Nernatus oligospilus Forster. This is the first record of Nematinae from southern Africa. A diagnosis is provided and distribution, biology and economic relevance are discussed. Natural enemies of the sawfly include the parasitoids Dibrachys sp. and Pteromalus sp. (Pteromalidae) and Pediobius sp. (Eulophidae) (Hymenoptera), and the predator Macrorhaphis sp. (Hemiptera: Pentatomidae). Field surveys indicated that the indigenous willow, S. mucronata Thunb., is not attacked. A greenhouse trial demonstrated that the sawfly cannot breed on the economically important saIicaceous tree Populus deltoides Bart. ex Marsh.


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