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

Kanzaki N, Tanaka SE, Ito M, Tanaka K, Slippers B, Tabata M. (2018) Some additional bionomic characters of Deladenus nitobei. Nematology 10.1163/15685411-00003168
Barnes I, Fourie A, Wingfield MJ, Harrington TC, McNew DL, Sugiyama LS, Luiz BC, Heller WP, Keith LM. (2018) New Ceratocystis species associated with rapid death of Metrosideros polymorpha in Hawai`i. Persoonia 40:154–181. 10.3767/persoonia.2018.40.07
Dittrich-Schröder G, Hoareau TB, Hurley BP, Wingfield MJ, Lawson S, Nahrung HF, Slippers B. (2018) Population genetic analyses of complex global insect invasions in managed landscapes: a Leptocybe invasa (Hymenoptera) case study. Biological Invasions 10.1007/s10530-018-1709-0
Viljoen E, Odeny DA, Coetzee MPA, Berger DK, Rees DJG. (2018) Application of Chloroplast Phylogenomics to Resolve Species Relationships Within the Plant Genus Amaranthus. Journal of Molecular Evolution 86(3-4):216-239. 10.1007/s00239-018-9837-9
Pham NQ, Barnes I, Chen SF, Pham TQ, Lombard L, Crous PW, Wingfield MJ. (2018) New species of Cylindrocladiella from plantation soils in South-East Asia. MycoKeys 32:1-24. 10.3897/mycokeys.32.23754 PDF