BEATING the BUG

Shot Hole Borer, which is decimating many of our trees, is of concern to everyone, especially gardeners. Here are some of the treatments currently being used

- CONNALL OOSTERBROEK

The Polyphageous Shot Hole Borer (PSHB), an ambrosia beetle, attacks living trees, digging tunnels and cultivating the fusarium fungus that its offspring feed on. The fungus spreads through the tunnels, blocking the tree’s vascular system, more often than not killing it.

Despite wide press coverage of the devastation the beetle, and its symbiotic partner, the fungus, can cause to both agriculture and domestic environments, there is still quite a bit of confusion on how to combat and control this problem.

Injection

Injecting individual trees with a cocktail of insecticide, fungicide, and fertiliser was one of the first methods that arborists used to treat infected trees. “Holes are drilled around the tree above the base, and the active ingredients injected into the tree are distributed via its vascular flow. This method of administering the treatment directly into the tree means there is less chance of contaminating the environment,” says Julian Ortlepp of Tree Works. To prevent the beetles from developing a resistance to the chemicals, a schedule of rotational treatments has to be implemented. “Injections should only be done once a year and can’t continue indefinitely,” warns Julian. While this method is still used, it’s expensive.

Fungicidal spray