Borer beetle facts

What to look out for

Signs across species differ: thousands of pin-prick holes appear on maples, whose trunks get blackish marks like cigarette burns. On oak trees, a fine sawdust fills cracks in the bark. Plane trees develop brownish stains that can become calloused over time.

Biological control agent

Biological control agent Dr Guy Preston, deputy director of environmental programmes for the department of environmental affairs, said: “We are investing heavily in opportunities to find biological control agents but it will not be a quick process.” Microbiologist Wilhelm de Beer said it would take at least three to five years to achieve this. Californian researchers had found a promising wasp but they cannot breed it in the lab.