Nofemela and Kfir (2005) report eight species of native parasitic Hymenoptera
attacking various life history stages of the invasive Plutella xylostella (Diamondback
Moth), with parasitism rates reaching 100% in some samples (see Le Roux et al.
2020, Chap. 14, Sect. 14.2.4).
South African biological control programmes have contributed significantly
to the control of 34 invasive plant species, 14 of which are considered to be
under complete control (Klein 2011), with the most prominent successes being
against Australian Acacia species (Box 7.1), cacti and several floating aquatic
plants.
Recent assessments of the economic benefits derived from the biological control
of invasive alien plants indicate that existing programmes have already reduced
management costs by ZAR 1.38 billion, and have the potential to double these
savings (Zachariades et al. 2017). The introduction of invertebrate biological control
agents has thus already contributed substantially to the management of invasive alien
plants and animals and further investment in the development of new agents can only
increase this contribution in the future.
Box 7.1 The Varroa Mite: A Destructive Parasite of Honey Bee
Colonies
The Varroa Mite (Varroa destructor) is an external parasite, and is one of the
world’s most devastating pests of honeybees. Female mites enter bee brood
cells and lay their eggs on developing larvae. Young mites hatch at about the
same time as the bees and leave the cells with the host, spreading to other bees
and larvae. Adult mites suck the haemolymph of honeybees, leaving wounds
and transmitting viral diseases. Infected colonies typically collapse after
1–2 years.
Varroa mites originated in Asia, but are now almost cosmopolitan in
distribution, reaching all continents except Australasia, and have had dramatic
impacts on the apiculture industry, resulting in billions of dollars in economic
loss globally (Cook et al. 2007). Their introduction to South Africa was
relatively recent, the first reports being from the Western Cape in 1997.
Subsequent spread has, however, been rapid, probably aided by movement
of colonies by commercial beekeepers. The mite now occurs throughout the
region and in both wild and commercial bee colonies, although it is thought to
have less impact on African races of Apis mellifera (Honey Bee) than on
European races, and has less impact in more tropical regions, such as in the
northern parts of South Africa, than in temperate ones, such as in the Cape
(Allsopp 2004). Synthetic varroacides are used to treat infected commercial
colonies (figure below).
(continued)
7 Alien Terrestrial Invertebrates in South Africa
193
attacking various life history stages of the invasive Plutella xylostella (Diamondback
Moth), with parasitism rates reaching 100% in some samples (see Le Roux et al.
2020, Chap. 14, Sect. 14.2.4).
South African biological control programmes have contributed significantly
to the control of 34 invasive plant species, 14 of which are considered to be
under complete control (Klein 2011), with the most prominent successes being
against Australian Acacia species (Box 7.1), cacti and several floating aquatic
plants.
Recent assessments of the economic benefits derived from the biological control
of invasive alien plants indicate that existing programmes have already reduced
management costs by ZAR 1.38 billion, and have the potential to double these
savings (Zachariades et al. 2017). The introduction of invertebrate biological control
agents has thus already contributed substantially to the management of invasive alien
plants and animals and further investment in the development of new agents can only
increase this contribution in the future.
Box 7.1 The Varroa Mite: A Destructive Parasite of Honey Bee
Colonies
The Varroa Mite (Varroa destructor) is an external parasite, and is one of the
world’s most devastating pests of honeybees. Female mites enter bee brood
cells and lay their eggs on developing larvae. Young mites hatch at about the
same time as the bees and leave the cells with the host, spreading to other bees
and larvae. Adult mites suck the haemolymph of honeybees, leaving wounds
and transmitting viral diseases. Infected colonies typically collapse after
1–2 years.
Varroa mites originated in Asia, but are now almost cosmopolitan in
distribution, reaching all continents except Australasia, and have had dramatic
impacts on the apiculture industry, resulting in billions of dollars in economic
loss globally (Cook et al. 2007). Their introduction to South Africa was
relatively recent, the first reports being from the Western Cape in 1997.
Subsequent spread has, however, been rapid, probably aided by movement
of colonies by commercial beekeepers. The mite now occurs throughout the
region and in both wild and commercial bee colonies, although it is thought to
have less impact on African races of Apis mellifera (Honey Bee) than on
European races, and has less impact in more tropical regions, such as in the
northern parts of South Africa, than in temperate ones, such as in the Cape
(Allsopp 2004). Synthetic varroacides are used to treat infected commercial
colonies (figure below).
(continued)
7 Alien Terrestrial Invertebrates in South Africa
193