An extremely wide range of host tree
species
Astonishingly, surveys in two botanical
gardens in Los Angeles have shown that the
beetle-fungus complex can infest more than
200 tree species from 58 plant families. This is
quite unusual; forest pests usually affect trees
of the same genus or family.
The lists of infested trees from California
include important crop trees like avocado,
macadamia, pecan, peach, orange and
grapevine. Some of the susceptible trees are
South African species that have been planted
in the Los Angeles botanical gardens. These
included the cabbage tree, common calpurnia,
monkey plum, dwarf and common coral trees,
and the honey flower, also sometimes called
kruidjie-roer-my-nie.
During the past week scientists and
government officials, representing the
Department of Agriculture, Forestry and
Fisheries and the Johannesburg City Parks and
Zoo met with our team to discuss next steps. A
working group has been set up to co-ordinate
monitoring the spread of the beetle and
managing research efforts. It will also advise
government agencies, municipalities, industry
and private tree growers.
Next steps
The public can help, too. We’ve made an
appeal to gardeners to watch out for the
beetles. Details including photographs of
the symptoms, GPS coordinates or a street
address, the host tree species and the
reporter’s contact details can be sent to
[email protected].
The fact that native South African tree species
are susceptible is particularly worrying.
Although the California study provided
some clues about the range of tree species
susceptible, scientists simply don’t know and
cannot predict what the beetle and fungus will
do in South Africa – on crops like avocado or
on native trees. We’re also appealing to people not to spread
the problem by moving plant material with
signs of beetle infestation. Instead, infested
branches should be cut into small pieces
and put into refuse bags, sealed and kept in
direct sunlight. The heat from the sun will kill
the insect and its larvae. Alternatively, wood
should be burnt on site.
This has prompted the institute to start several
research projects that range from developing
fast DNA-based diagnostic tools for the fungus
and beetle, to possible control measures. A working group has been set up to co-
ordinate monitoring the spread of the beetle
and managing research efforts. It will also
advise government agencies, municipalities,
industry and private tree growers.
Elevated blue-black lesions on a tree’s bark,
resembling shotgun wounds or cigarette
burns, indicate borer beetle infestation.
Image: George Municipality
The public can help, too. We’ve made an
appeal to gardeners to watch out for the
beetles. Details including photographs of
the symptoms, GPS coordinates or a street
address, the host tree species and the
reporter’s contact details can be sent to
[email protected].
We’re also appealing to people not to spread
the problem by moving plant material with
signs of beetle infestation. Instead, infested
branches should be cut into small pieces
and put into refuse bags, sealed and kept in
direct sunlight. The heat from the sun will kill
the insect and its larvae. Alternatively, wood
should be burnt on site.
Acknowledgement:
Wilhelm de Beer, Associate Professor,
University of Pretoria: A tiny beetle and
its deadly fungus is threatening South
Africa’s trees originally published in
, February 27, 2018
https://theconversation.com/a-tiny-beetle-and-
its-deadly-fungus-is-threatening-south-africas-
trees-92050 Republished under Creative
Commons License
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