NAME: Solanum mauritianum
COMMON NAME: Bugweed, Flannel weed, Woolly nightshade, Luisboom
ORIGIN: South America
REASON FOR INTRODUCTION IN SOUTH AFRICA: Ornamental value
INVASIVE STATUS IN SOUTH AFRICA: CARA 2002 Category 1, NEMBA Category 1b
DESCRIPTION: It has a dense covering of soft, white hairs on the stems, flower stalks and underside of the leaves. The leaves are large and soft, especially when growing in the shade; they can reach a length of 250 mm, the upper surface being dull green and velvety, while the lower surface is white and felty. Purple to lilac flowers are borne in terminal clusters and give rise to round berries, approximately 10 mm diameter, which change from green to yellow when ripening. The berries, which are popular amongst frugivorous birds, contain an abundance of seeds. These are dispersed in the droppings of the birds, resulting in large numbers of seedlings germinating in disturbed habitats kilometres from the mother plant
PROBLEM: Bugweed invades forest margins, plantations, roadsides, urban spaces, but also sparsely forested ravines in protected areas. Besides shading out indigenous vegetation, bugweed causes great economic losses in timber and sugar cane plantations. Its hairs act as skin and respiratory irritants, and the unripe berries are toxic, fruit also act as hosts for fruitfly.
CONTROL: Small plants can be uprooted manually, and large plants may be ringbarked at ground level, or cut down close to the ground and the stumps treated with recommended herbicides. The seeds of inaccessible plants will, however, always cause re-invasion of cleared areas, and biocontrol is therefore deemed the most sustainable control option. The natural enemies of Solanum species are notorious for their lack of host-specificity, and decades of research (initially at ARC-PPRI and later at University of KwaZulu-Natal) into effective, host-specific biocontrol agents have culminated in the release of only two insect agents: a leaf-feeding lacebug, Gargaphia decoris, and a flower-bud feeding snoutbeetle, Anthonomus santacruzi.