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Explora: Environment
and Resource Data should determine biocontrol success

Table 1. All Australian Acacia species subjected to weed biocontrol in the world
Weed Biological control agent Feeding Released Date first Damage to
guild released weed
Acacia longifolia Trichilogaster acaciaelongifoliae (Frogatt) Bud galler South Africa 1982 Extensive*
(Andr.) Willd. Portugal 2015 Not assessed
New Zealand 2022 Not assessed
Melanterius ventralis Lea Seed feeder South Africa 1985 Extensive
Acacia melanoxylon Melanterius acacia Lea Seed feeder South Africa 1986 Extensive*
R.Br.
Acacia cyclops Melanterius servulus Pascoe Seed feeder South Africa 1994 Considerable*
A.Cunn.exG.Don Dasineura dielsi Rübsaamen Flower galler South Africa 2001 Extensive*
Acacia mearnsii De Melanterius maculatus Lea Seed feeder South Africa 1994 Considerable*
Wild. Dasineura rubiformis Kolesik Flower galler South Africa 2006 Considerable*
Acacia dealbata Link Melanterius maculatus Lea Seed feeder South Africa 1998 Moderate
Dasineura pilifera Kolesik Flower galler South Africa 2016 Not assessed
Acacia decurrens Melanterius maculatus Lea Seed feeder South Africa 2001 Moderate
(Wendl.)
Acacia saligna Uromycladium morrisii Doungsa-ard, Gall former South Africa 1987 Extensive*
(Labill.) H.L.Wendl. McTaggart, Geering and R.G.Shivas
Melanterius castanaeus Lea Seed feeder South Africa 2001 Extensive
Acacia pycnantha Trichilogaster signiventris (Girault) Bud galler South Africa 1987 Extensive*
Benth. Melanterius maculatus Lea Seed feeder South Africa 2003 Not assessed
Acacia baileyana Melanterius maculatus Lea Seed feeder South Africa 2006 Not assessed
F.Muell. Dasineura pilifera Kolesik Flower galler South Africa 2016 Not assessed
Acacia podalyriifolia Melanterius maculatus Lea Seed feeder South Africa 2008 Not assessed
A.CunnexG.Don
Notes: Information extracted from Impson et al. 10,31 Damage to weed supplemented with Zachariades et al. (most recent assessment). The asterisk (*)
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indicates biological control agents on plant species, providing ‘substantial’ control and thereby reducing other management measures to be used.

for these plants has occurred. Henderson and Wilson that despite biocontrol agent presence and impact, these
30
claimed that the rate of spread of invasive Australian Acacia invasive plants have maintained their population density
spp. had been reduced by their released biocontrol agents and area of occupancy. Furthermore, the data also suggests
through having compared this to the relative rate of spread that these invasive plants can still spread into and establish
of other invasive plants in South Africa. The validity of this in previously unoccupied suitable habitats. Biocontrol
comparison is questionable, as the authors were comparing agents should also not be the only factor to consider when
plants with different growth forms, longevity, and stages of assessing a change in the area of occupancy or rate of
invasion. A reduction in the rate of spread for many of the spread of invasive plants in their invaded range. In the case
invasive Australian Acacia spp. may also not be of relevance of invasive Australian Acacia spp., the influence of large-
as they are in the last stage of the invasive process, having scale mechanical clearing operations under the auspices of
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now occupied the most suitable habitats. Rouget et al. the working for water program, use of fire wood (main
38
indicated that at least for Acacia mearnsii and Acacia saligna, source in Western Cape), land use change (e.g., residential
a reduced rate of spread will not be meaningful in curbing and agricultural development), and frequent disturbance
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their invasive status in South Africa. This is because these events (e.g., fire) should also be considered. To date,
plants have already realized their potential distribution only biocontrol has been considered a potential factor
in South Africa. Therefore, there has been no indication, influencing the area occupied by invasive Australian Acacia
based on distributional data, that the released biocontrol with a total disregard for any other potential factors. 30
agents on invasive Australian Acacia have been successful Besides the methodological challenges associated with
in reducing the area of occupancy or rate of spread of their the current distributional data, it can also be argued that
hosts. On the contrary, distributional data have suggested no decline in the invaded ranges of these plants has been

Volume 2 Issue 1 (2025) 4 doi: 10.36922/eer.5876