We have just published the SHOT HOLE BORER “WHAT TO DO” GUIDE that contains a practical guideline on the options that are available for private residents to treat their own trees. This guide does not endorse any specific products, nor does it represent an easy solution to the PSHB crisis South Africa is currently experiencing.
View the guide here: PSHB.co.za/what-to-do/
A combination of insecticides and fungicides is required
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.
Currently there are no chemical products registered for use against PSHB in South Africa. A combination of insecticides and fungicides is required.
Chemical formulations with specific active ingredients have been shown to be effective in US trials, some of these are:
- Emamectin Benzoate (systemic insecticides)
- Imadacloprid (systemic insecticide)
- Cypermethrin (non-systemic insecticide) – short acting with a strong repellent effect against insects
- Tebuconazole (fungicide)
- Propiconazole (fungicide)
Products derived from natural sources can help your tree:
- Neem oil has been identified as having an effective repellent effect
- Salicylic acid (Asprin) triggers an immune response in plants that may improve your tree resistance to PSHB
Common sense needs to be combined with practical experience. Contact your local nursery and inquire about available products that can boost your tree’s health.
The following article details a US study to evaluate treatment options against the polyphagous shot hole borer beetle, and provide insights into the need for a combination of injection and contact treatment:
National Center for Biotechnology Information – Journal Article
Evaluations of Insecticides and Fungicides for Reducing Attack Rates of a new invasive ambrosia beetle (Euwallacea Sp., Coleoptera: Curculionidae: Scolytinae) in Infested Landscape Trees in California
“The combination of a systemic insecticide (emamectin benzoate), a contact insecticide (bifenthrin), and a fungicide (metconazole) provided some level of control when applied on moderate and heavily infested trees.”
Public Trees vs Private Trees
Viability of treatment protocols differ between public and private trees, poison exposure needs to be considered and cost-benefits evaluated. The total cost of loosing a mature urban tree needs to be measured against the costs of removal, replacement and maintenance time to reach maturity.
In 2010 the “Greening Soweto” project was launched which aimed to plant more than 300,000 trees – this project was supported by Johannesburg City Parks as a fundamental trans-formative initiative for the city – now that these trees have been found to be infested by PSHB they require urgent treatment.
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” vs “Crown Spray and Soil Drench”
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.
Do you need help? We can recommend a service provider in your area who knows how to treat PSHB?