Box 4.2 Release of the First Biological Control Agent Against Egeria
densa
Egeria densa (Brazilian Waterweed), first recorded in South Africa in 1963
from the Durban area, is currently regarded as the most widely distributed
submerged invasive aquatic plant species in South Africa. It forms dense
populations in slow-moving rivers, and impoundments. The species is native
to South America, and was most likely introduced to South Africa via the
aquarium and ornamental plant trade. It is still traded in South Africa, despite
its status as a Category 1b invasive (see Box 1.1 in van Wilgen et al. 2020,
Chap. 1, for a definition of categories), increasing the propagule pressure on
South African waterbodies.
A biological control programme was initiated against E. densa in 2014,
following the identification of the leaf-mining fly H. egeriae as a potential
agent by Cabrera-Walsh et al. (2013) (figure below). The initial research
into the biology and host specificity of the fly was followed by its importation
into the USA as a candidate control agent, after which it was imported into
First release of the leaf mining fly, Hydrellia egeriae (Diptera: Ephydridae), against Egeria
densa (Brazilian Waterweed) on the Nahoon River in East London. (Photo: J.A. Coetzee).
Inset A: adult fly, inset B: fly larva in a leaf mine. (Photographs courtesy of R. Smith)
(continued)
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M. P. Hill et al.
densa
Egeria densa (Brazilian Waterweed), first recorded in South Africa in 1963
from the Durban area, is currently regarded as the most widely distributed
submerged invasive aquatic plant species in South Africa. It forms dense
populations in slow-moving rivers, and impoundments. The species is native
to South America, and was most likely introduced to South Africa via the
aquarium and ornamental plant trade. It is still traded in South Africa, despite
its status as a Category 1b invasive (see Box 1.1 in van Wilgen et al. 2020,
Chap. 1, for a definition of categories), increasing the propagule pressure on
South African waterbodies.
A biological control programme was initiated against E. densa in 2014,
following the identification of the leaf-mining fly H. egeriae as a potential
agent by Cabrera-Walsh et al. (2013) (figure below). The initial research
into the biology and host specificity of the fly was followed by its importation
into the USA as a candidate control agent, after which it was imported into
First release of the leaf mining fly, Hydrellia egeriae (Diptera: Ephydridae), against Egeria
densa (Brazilian Waterweed) on the Nahoon River in East London. (Photo: J.A. Coetzee).
Inset A: adult fly, inset B: fly larva in a leaf mine. (Photographs courtesy of R. Smith)
(continued)
108
M. P. Hill et al.