Ph. © Brett Hurley, FABI

Forest invasive species in Africa

The arrival of non-native species has increased exponentially in Africa, as in other parts of the world. This is attributed mainly to the increase in travel and trade, and is influenced by difficulties in implementing adequate quarantine regulations. Once introduced into the continent, invasive species are likely to spread to neighbouring countries, sometimes spreading across a vast area in an alarmingly short period.

Thus, many, and perhaps most, of non-native invasive species are shared between a number of African countries. This results in many challenges, but also provides opportunities for countries to collaborate towards management of these species.

Invasive species of forests include insects, microbes, other animals and plants. The list below provides examples of some of the current main invasive species, with a focus on invasive species of plantation forests. Further information and publications on these invasive species can be obtained in the section Resources or - more specifically - from FABI Resources and CABI Compedium on invasive species.

African invasive species

Click on the pest name to expand the descriptive section.

 

Gonipterus sp.2
Eucalyptus weevil, snout beetle

Host: Eucalyptus (eucalypt species)
First report in sub-Saharan Africa: 1916 (South Africa)
Photo:       Adult Gonipterus sp.2 on Eucalyptus stem (© Brett Hurley)

 
 

Description: the adult beetles are brown to red-brown, about 8-9mm in length and have a characteristic ‘X’ marking on the back. The larvae are yellow to yellow-orange, about 10mm when fully-grown, legless, with black spots and two black lateral stripes. The larvae produce a thin thread of excrement when feeding. The eggs are light yellow, about 1mm in length and 0.5mm in width. The eggs are deposited horizontally in rows and covered with excremental material to form a hardened dark brown egg capsule.
Symptoms: both the foliage and young shoots of Eucalyptus trees are eaten by Gonipterus. The damage caused may result in stunted growth and tree mortality in severe cases. Adults feed primarily along the leaf margin, resulting in a characteristic scalloped appearance of the leaves. Both the adult and larval stages prefer new growth.
Management: selection of more tolerant planting material is possible. A biological control agent, the egg parasitoid Anaphes nitens, has been released in some countries.


Glycaspis brimblecombei
Red gum lerp psyllid

Host: Eucalyptus (eucalypt species)
First report in sub-Saharan Africa:
2012 (South Africa
)
Photo: Lerps of Glycaspis brimbelcombei on Eucalyptus leaf (© Brett Hurley)

 

Description: small sap-sucking insect (2.5-3.1mm). The nymph has a flattened body and is covered with a white conical shelter (lerp) of wax and sugar. Adults are winged and disperse widely.
Symptoms: infested leaves are covered with waxy secretions and honeydew, on which sooty mould grows. Feeding results in drooping leaves and drying of leading shoots and heavy infestations can totally defoliate and kill trees.
Management: selection of resistant planting material. The parasitic wasp Psyllaephagus bliteus, has been reported in a number of African countries, assumed to have been unintentionally introduced with the pest.


Leptocybe invasa
Bluegum chalcid

Host: Eucalyptus (eucalypt species)
First report in sub-Saharan Africa: (2002) Kenya and Uganda
Photo: Gall of Leptocybe invasa on Eucalyptus petiole (© Brett Hurley)

 

Description: a small wasp; average length of 1.2mm. Head and body are brown in colour with a slight to distinct blue to green metallic shine.
Symptoms: causes galls on the mid-ribs of leaves, and on the petioles and stems, resulting in the curling of leaves and malformation of stems. Severe infestations result in ‘feathering’ of leaves, stunted growth, and possible death of small trees.
Management: selection of more resistant planting material is possible. A biological control agent, the parasitic wasp Selitrichodes neseri, has been released in some countries.


Ophelimus maskelli
Eucalyptus gall wasp

Host: Eucalyptus (eucalypt species)
First report in sub-Saharan Africa: (2014) South Africa
Photo: Galls of Ophelimus maskelli on Eucalyptus leaves (© Brett Hurley)

 

Description: small brownish-black wasps, 0.83 - 1.07mm in length.
Symptoms: causes small green to reddish blister-like galls on both sides of the leaf blade; gall diameter ranging in size from 0.9 - 1.2mm. Heavy galling may result in premature shedding of the leaves.
Management: selection of resistant planting material is possible. The parasitic wasp Closterocerus chamaeleon, has been reported in South Africa, assumed to have been unintentionally introduced with the pest.


Pissodes sp.
Deodar weevil

Host: Pinus (pine species)
First report in sub-Saharan Africa: (1942) South Africa
Photo: Larvae of Pissodes sp. in pupal chamber, under bark
 (© Brett Hurley)

 

Description: adults have long, curved snouts and are reddish brown in colour with two patches of light grey scales on their backs. The body length of the adults ranges from 6-8mm. The larvae are yellowish white, cylindrical and legless, with light brown heads, and they are about 6mm long when fully grown.
Symptoms: dying or dead pine shoots, often resulting in forking or branching of trees. Circular emergence holes on the bark of the main stem, which DO NOT penetrate the wood. These exit holes lead from the pupal chambers or ‘chip cocoons’ between the bark and the wood.
Management: remove dying and dead trees, as these provide host material for the population of the beetle to increase. A native parasitoid has been detected parasitising the larvae.


Sirex noctilio
Sirex woodwasp

Host: Pinus (pine species)
First report in sub-Saharan Africa: (1994) South Africa
Photo: Female of Sirex noctilio ovipositing into wood of pine tree (© Brett Hurley) 

 

Description: the adult wasps are metallic blue with two pairs of membranous wings. The female adult has a pointed projection at the rear of the abdomen that covers the ovipositor (egg tube). The male has a broad orange band covering most of its abdomen. The length of the adult ranges from 10-40mm. The larvae are creamy white in colour and have a characteristic dark spike at the posterior end. The larvae are found in the sapwood.
Symptoms: wilted pine needles, first turning yellow and then brown. Small resin droplets on the bark of infested stems. Circular emergence holes of adults which go through the bark and into the sapwood; from about 3-10mm in diameter. Larval tunnels in sapwood.
Management: silvicultural practices to increase vigour of trees within stand, including thinning to remove the stressed and sub-dominant trees that are the primary host of Sirex. Biological control agents, including the parasitic nematode Deladenus siricidicola and the parasitic wasp Ibalia leucospoides, have been released.


Spondyliaspis plicatuloides
Shell lerp psyllid

Host: Eucalyptus (eucalypt species)
First report in sub-Saharan Africa: (2014) South Africa
Photo: Shell-shaped lerps of Spondyliaspis plicatuloides (
© Brett Hurley)

Description: small sap-sucking insect. The nymphs are reddish-orange in colour and are covered with a brown sea shell-like shelter, called a lerp. The adults are winged and reddish-brown in colour.
Symptoms: brown sea shell lerps and reddish lesions on leaf surface.
Management: selection of resistant planting material. The natural enemy of Glycaspis brimblecombei has been reported to also parasitize the shell lerp psyllid.


Thaumastocoris peregrinus
Bronze bug

Host: Eucalyptus (eucalypt species)
First report in sub-Saharan Africa: (2003) South Africa
Photo: Adult Thaumastocoris peregrinus on Eucalyptus leaf (© Brett Hurley)

Description: adults are small (2-4mm), light-brown sap-sucking insects. Eggs are small, oval and black, and can be laid singly or in clusters.
Symptoms: initial reddening of the canopy leaves which become reddish-yellow or yellow-brown, coupled with some leaf loss and the visible abundance of adults, nymphs and black egg capsules in clusters. During severe infestations, loss of leaves leads to canopy thinning and branch dieback.
Management: An egg parasitoid wasp, Cleruchoides noackae, has been released in some countries.

last updated:  Friday, June 7, 2019