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Galls are abnormal growths on a plant that can have various causes, including viruses, nematodes, bacteria, fungi, mites and insects. Aphids, flies and wasps are some of the insects known to cause galls. Generally plants can tolerate galls with no obvious injury. However, a very high incidence of galls can damage and even kills plants.

Gall formers on eucalypts

The Eucalyptus gall wasp (Leptocybe invasa) is currently the only gall forming insect in South Africa which is considered a serious pest of plantation forest trees. This insect, which infests Eucalyptus, was accidentally introduced from Australia. It was first detected in South Africa in 2007 (and only in 2009 in forestry areas). The Eucalyptus gall wasp causes galls on the stems, petioles and midrib of leaves. Damage by this insect is particularly severe on younger trees, where the majority of leaves can have galls, resulting in severe leaf drop. In such cases, stunting of growth and possibly tree death can occur. The adult wasp is minute (about 1.4 mm), but the galls, which often contain multiple eggs of the Eucalyptus gall wasp, are easily visible. Severely infested trees have a gnarled appearance.

New Publications

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Human ZR, Crous CJ, Roets F, Venter SN, Wingfield MJ, de Beer ZW. (2017) Biodiversity and ecology of flower-associated actinomycetes in different flowering stages of Protea repens. Antonie van Leeuwenhoek 10.1007/s10482-017-0942-3
Wingfield BD. (2017) The peer review system has flaws. But it’s still a barrier to bad science. The Conversation http://bit.ly/2holsgS
McTaggart AR, Beasley DR, Wingfield MJ, Wood AR, Pretorius ZA, Drenth A, Shivas RG, Roux J. (2017) A dynamic, web-based resource to identify rust fungi (Pucciniales) in southern Africa. MycoKeys 26:77-83. 10.3897/mycokeys.26.14602
De Maayer P, Aliyu H, Vikram S, Blom J, Duffy B, Cowan DA, Smits THM, Venter SN, Coutinho TA. (2017) Phylogenomic, pan-genomic, pathogenomic and evolutionary genomic insights into the agronomically relevant enterobacteria Pantoea ananatis and Pantoea stewartii. Frontiers in Microbiology 8(1755) 10.3389/fmicb.2017.01755
Jami F, Wingfield MJ, Gryzenhout M, Slippers B. (2017) Diversity of tree-infecting Botryosphaeriales on native and non-native trees in South Africa and Namibia. Australasian Plant Pathology 10.1007/s13313-017-0516-x