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A MINUTE alien invader from Asia is posing a very serious threat to both ornamental and fruit trees in South Africa. The Polyphagos Shot Hole Borer Beetle, might only be 2 mm long but it carries with it several fungus species.
One in particular, Fusarium euwallacea, will eventually kill a beetle infested tree. There are no known natural controls nor effective insecticides that will effectively kill infestations of this beetle.
Of great concern is that infestations of the Shot Hole Borer have been found in an avenue of London Plane trees in the KZN National Botanical Gardens in Pietermaritzburg.
Not only does this beetle pose a threat to both certain exotic ornamental trees but of greater concern is the fact that it invades and will eventually kill a number of indigenous trees as well as certain commercially grown nut and fruit trees.
This has serious environmental and economic implications for South Africa’s indigenous forests as well as for agriculture respectively.
To list some of the indigenous trees affected by the Shot Hole Borer and its attendant fungus these species are as follows: Outeniqua yellowwood, Thorn tree (Acacia/Senegalia) species, Kiepersol or cabbage tree and coral tree species.
Possibly of greatest economic gravity is the beetle’s invasion of crop bearing trees such as avocados, macadamias, pecans, peaches, oranges and grapevines.
An appeal has been made to the public to be vigilant of the symptoms indicating the presence of Shot Hole Borer. These vary from patches of white, powdery wood (frass) around the tree or on the trunk, blotches of oozing resin at the beetles’ entrance hole and/or small raised lesions on the bark.
Farmers, gardeners and the general public are encouraged to be pro-active in reporting any suspected infestations with photographs of symptoms; GPS co-ordinates or a street address; the host tree species and personal contact details to diagnostic.clinic@fabi.up.ac.za
It is known that the Shot Hole Borer Beetle is sensitive to heat.
Therefore, the best method of eradication at present is to remove infested branches.
Either burn these immediately or cut into smaller pieces, place in sealed refuse bags and leave in direct sunlight so the heat will kill the larvae and the insect.
