The first comprehensive study mapping the distribution and genetic diversity of invasive Eucalyptus insect pests in sub-Saharan Africa confirms the presence of five major foliage-feeding species in 14 countries. The results of this study which was led by Prof. Brett Hurley and Prof. Bernard Slippers and run by Dr Mesfin Gossa, a postdoctoral Fellow at the University of Pretoria’s Forestry and Agricultural Biotechnology Institute, have implications on the quarantine, future research and management of these pests on the continent and beyond.
In collaboration with foresters and entomologists across 14 countries, the researchers collected insects from Eucalyptus plantations and identified them using morphological characters and mitochondrial DNA sequence data. The study was conducted in 14 Eucalyptus-growing countries including Democratic Republic of Congo (DRC), Ethiopia, Ghana, Kenya, Madagascar, Malawi, Mauritius, Reunion, Sierra Leone, South Africa, Uganda, Zambia and Zimbabwe. The first publication from this project recently appeared in the journal, Biological Invasions.
The researchers confirmed the presence of Leptocybe invasa, Glycaspis brimblecombei, Thaumastocoris peregrinus, Gonipterus sp.n.2 and Ophelimus maskelli. According to the authors, these insect pests “inevitably pose a serious threat to the sustainability of Eucalyptus forestry in the region.” Four of these pests, namely L. invasa, G. brimblecombei, T. peregrinus, and Gonipterus sp.n.2 were found broadly distributed across the sampled countries, with first reports in many of those countries.” They described O. maskelli as a “recent arrival” to the region and confirmed its presence in four countries.
Regarding the distribution of pests:
- The researchers confirmed the presence of L. invasa in 13 countries, except DRC. It was reported for the first time in Madagascar, Mauritius and Reunion, Sierra Leone and Zambia.
- Glycaspis brimblecombei was confirmed in 11 of the 14 countries. It was reported for the first time in Kenya, Malawi, Reunion, Rwanda and Uganda
- Of of the 11 countries where T. peregrinus was confirmed present, it was reported for the first time in five of them, viz. DRC, Madagascar, Mauritius, Rwanda and Zambia.
- One the earliest arrivals in the region, Gonipterus sp.n.2 was confirmed present in Kenya, Rwanda, South Africa and Zimbabwe. In Rwanda, it was reported for the first time.
- The gall forming wasp, O. maskelli was confirmed only in Ethiopia, Madagascar, Rwanda and South Africa. It was reported for the first time in Madagascar and Rwanda.
- Except L. invasa, none of the other insect pests were detected in Ghana and Sierra Leone
Genetic diversity analysis revealed:
- Of the three haplogroups detected across the entire range of the L. invasa, at least two haplogroups (A and B ) were found overlapping in five countries, including Ghana, Malawi, Sierra Leone, South Africa and Zimbabwe
- Only a single haplotype of G. brimblecombei was detected in the region
- Four closely-related haplotypes of T. peregrinus were detected
- Two closely related haplotypes of Gonipterus sp.n.2 were found in the region. One of these haplotype (haplotype Q) was found exclusively in the sub-Saharan shared between Kenya and Rwanda, while the second one (haplotype V) was detected in South Africa and Australia
- The study confirmed the presence only a single haplotype of O. maskelli across the region
In general, the authors highlight that the current relatively low genetic diversity of the pests in the region suggests the possibility of using the same or similar management strategies across the invasive range of these insects and encourages collaborations between countries. They also stressed that capacity building across sub-Saharan Africa and collaboration among experts are essential to address these and similar problems.