Polyphagous Shothole Borer (PSHB)

Wees maar op die uitkyk vir hierdie bedrieglike klein boordertjie wat baie skade aanrig sover hul gaan.   Hulle het ook met gemak in ons boomryke tuine en strate in Suid-Afrika ingevaar.  Verskeie bome is al geaffekteer en het gevrek.  Boere moet op die uitkyk wees vir tekens wat voorkom.  Die gedroggie boor tonnels, maar dis egter die swamme wat in die tonnels groei wat die skade aanrig – (Fusarium euwallaceae).  Larwes wat uitkom leef en teer op die swamme.

The discovery of this beetle and fungus in South Africa is of major concern to foresters, farmers and landscapers, as these organisms are known as aggressive tree killers. The PSHB is a 2 mm long ambrosia beetle that is native to Southeast Asia. The beetle carries several fungal species, one of which is Fusarium euwallaceae, with it when it infests new trees. It bores through the bark into the sapwood of the trees and inoculate the fungus into living wood. The fungus grows in the galleries (tunnels) of the beetle and serve as ‘vegetable garden’ for the beetle larvae, but in susceptible trees the fungus can spread through the sapwood causing disease or even death of the tree. In its native environment in Southeast Asia, it seems as if the beetle and fungus do not cause serious damage because tree species have evolved with the beetle-fungus complex and have resistance towards them. However, the beetle and fungus were somehow introduced into Israel and California during the past 15 years where they cause serious damage on especially Avocado trees.

Small creatures

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Private residents, community organisations, service providers and City Parks are joining hands to respond to the problem.

Infested and dead trees are a breeding ground for shot hole borer. Recent chemical tests indicate that one heavily infested tree contains over 100,000 beetles – these dead trees need to be removed and disposed of responsibly.

We need to fully notify government of the magnitude of this devastating invasion of this bug. Currently known area of established infestation are Johannesburg, Durban, Pietermaritzburg, George, Knysna  and Hartwater.

Affected trees develop wilted brown leaves on infested branches. The most obvious sign of infestation is that branches have brown stains around each hole where the borer has penetrated the tree.

It is important to note that the borer beetle itself does not kill the tree. The problem is the fungus (Fusarium euwallaceae) that grows in the tunnels made by the borer. Fusarium dieback occurs when your tree’s vascular system becomes blocked, leaves begin to thin on the ends of branches, they turn brown, the branch and eventually the tree will die.

Borende kewer

 

Mature urban trees such as the London Plane trees that encircle the entire Johannesburg Zoo are under attack – will these giant trees simply be chopped down, or will policy make provision for heritage public trees to receive treatment?Many streets in Johannesburg are now lined with dead trees, these must be removed and the infested wood disposed of responsibly. City Parks need to create controlled sites where infested wood can be burnt so that the beetles within do not emerge and fly further.

Tree injection is optimal for the treatment of public space trees since no poison is exposed once the treatment has been applied.

Surface application of chemical poisons pollutes the ecosystem, and makes the immediate area toxic. Pets walk under poisoned trees and accumulate poison on their feet, which subsequently get licked and ingested.

The Department of Agriculture, Forestry and Fisheries is in the process of declaring PSHB an invasive pest, this status will allow emergency registration of chemical treatments under Act 36.

A combination of insecticides and fungicides is required. The following pesticides can be used in a combinations treatment (refer to article below).

Insecticides
Emamectin Benzoate (most effective)
Imadacloprid
Cypermethrin (non-systemic spray with penetrating agent) – New local product under development – watch this space..!!

Fungicides
Tebuconazole
Propiconazole

Willow - 2015-05 BEFORE

Willow - 2016-02 AFTER

The beetle and its larvae feed off fungus that grows inside the tunnels that it makes, insecticides are not particularly effective against it since it does not ingest the wood.

Polyphagous Shot Hole Borer - Fungus inside the tunnels

Video

Whiteboard video explaining the Polyphagous Shot Hole Borer (PSHB) crisis in South Africa.
Visit http://www.PSHB.co.za for information
Thanks to the Quick2draw.co.uk team for creating the video.

 

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