Shothole Borer Beetle – an Ecological Tragedy
Life is a Garden has some essential information to share this month. The shot hole borer beetle, known also as Euwallacea fornicates, is a huge threat to South African biodiversity and our gardens are certainly no exception. From the 80 species of trees under attack, 20 of these are reproductive hosts for this most gagga gogga, and with so many trees in SA and in private gardens, the threat is closer to home than we may think. Here’s some must-know info to help save our trees!
How the shot hole borer operates
This invasive bugger from Asia is black in colour and smaller than a sesame seed (about 2mm long). Shot hole beetles dig tunnels in the trunks and branches of host trees where they then lay their eggs. The female beetle carries a fungus (Fusarium euwallaceae), which she spreads through these tunnels, which then becomes food for both larvae and adults.
What happens to our trees
The fungus spread inside tunnels completely disrupts the flow of water and nutrients of trees. Simply put, infected trees begin to die from the inside as the larvae hatch, digging through what’s left of the tree, and spreading more deadly fungus that causes trees to basically die from malnutrition. These beetles move a kilometre per week, rapidly infesting and reproducing.
Identifying an infected tree
Look out for signs of possible infestations by inspecting the trunks and branches of your trees and those in the surrounding area. Symptoms may vary across tree species, but here are the tell-tale indicators to take note of:
- Multiple round 1mm wide entry-holes, similar to paper punch holes.
- Dark, wet staining, oozing, and thick gumming around suspicious holes.
- Streaks of white powder, sugar volcanoes, or fine sawdust coming from trunk/branch holes.
- Wilting trees and dead branches.
Best course of action
Sadly, there is no known insecticide that is effective against the Shot Hole as they drill so deeply into the wood. We can only be proactive by preventing the spread of the beetle and removing the environment that allows them to reproduce. In other words,
- Start a watering and fertilising regime for your trees to make them as healthy as possible to withstand an attack. If a tree is strong enough, it can flood borer tunnels with gum or sap.
- Call in an arborist to advise if the tree is a valuable investment tree on your property.
- Any dead wood infested with shot hole borer beatles should be covered with thick plastic before moving. The moving of infested firewood is one of the biggest pathways to spreading this invasive species. Chip and solarise infected wood on site.
- Notify your neighbours and create awareness so that everyone is on board and informed.
- Report infected trees here: firstname.lastname@example.org
Did you know?
- 300+ Trees have had to be removed in JHB North.
- Shot hole borers love certain trees more and will always head to their favourite six species. This means that the most affected tree species are: London plane, Boxelder, Japanese and Chinese maple, English oak, and Liquidambar. Monitor these species closely in your garden and remove them as soon as branches begin to die.
- These six trees are regarded as target species for the shot hole borer. Once the beetles have colonised these trees with thousands of offspring - and the trees begin dying - the shot hole borers spread to nearby trees which are then infested.
- Country-wide surveys found that several fruit trees (including peach, olive, grapevine, guava, and fig) have been infested in urban areas.
- Indigenous tree species such as coral trees, wild olives, yellowwoods, and Natal figs, are the most threatened.
- Judging by the destruction in Knysna, as well as the rise of beetles in Sandton (one of the world’s largest urban forests with over 10 million trees), the shot hole could well be one of South Africa’s largest ecological tragedies of all time.
- The shot hole is currently infesting over 200 tree species from 28 plant families.
- These beetles are transported by humans through moving infested firewood – so burn or chip the wood and place it under plastic for six weeks in full sun (known as solarisation). Never move infested wood unless it is under a thick plastic tarpaulin. Otherwise, beetles fly off the back of a bakkie and infest all properties along the route to a garden dump.
Our country is one of the world’s largest biodiversity capitals and host to 299+ species of mammals and 858+ species of birds. These animals depend on our trees as a source of food and shelter. Check if you have any of the six targeted tree species in your garden and keep monitoring them closely.