The Forestry & Agricultural Biotechnology Institute (FABI) website page on PSHB has been updated. It provides a history of the infestation, the lifecycle of the PSHB beetle, and lists funded projects that tackle the challenge from different angles. It also provides strategies on how to respond to the infestation that echo some of those I have suggested, yet with more technical detail which is helpful.
Of particular interest to me is the clear statement that is it Fusarium Disease that eventually kills the trees, and that it is stressed trees that succumb to the fungal disease.
FABI Recommendations in Tackling PSHB and Fusarium Disease:
What can be done?
There is no way in which the PHSB invasion in South Africa can be stopped. However, some treatments and management strategies can reduce its impact.
Municipalities should:
· Train staff to recognize and cut down heavily infested reproductive host trees from streets and public areas
· Infested branches can be cut if the main stem is not infested (unlikely, as PSHB usually infests the stem first)
· Designate dedicated dumping sites where infested wood can be dumped as it poses a risk of spreading the beetle.
· Chip wood to pieces finer than 2 cm at the dumping sites.
· Provide a help desk (preferably online) where the public can report infested trees and get information.
Tree growers/home owners should:
· Try to determine whether the symptoms are really caused by PSHB (see FABI brochures)
· If unsure, ask help from municipal or other help desks, or your local arborist
· If the tree is a heavily infested reproductive host, cut it down
· Infested branches can be cut if the main stem is not infested (unlikely, as PSHB usually infests the stem first)
· Dump the wood at a dedicated (by your municipality) dumping site
· Chip the wood to finer than 2 cm, allow chips to compost by keeping it wet
· Or burn the wood on site (some beetles will fly away when the wood becomes hot or when smoke appears, so do not burn in uninfested areas)
· DO NOT MOVE FIREWOOD AROUND, ESPECIALLY NOT OUT OF THE INFESTED AREA WHERE YOU LIVE
· Or solarize (leave in full sun) chopped wood under thoroughly sealed clear plastic sheets for at least one month in summer or several months during winter
· At present no chemical product is registered (legal) to use on PSHB in South Africa.
However, municipalities that don’t provide designated dump sites render some of FABI’s suggestions purely academic and therefore not practically useful. Once municipalities do so, FABI and Blue Blue Earth will be on the same page.
Update on Pesticides: A Hopeful Note
As FABI notes, no chemical product specifically aimed at tackling PSHB or Fusarium Disease is registered in South Africa. It is therefore illegal to use any product that is unregistered.
Nonetheless, there are a number of applications with the Director of Emergency Poisons that might be able to do so; the director’s response remains important in listing what may safely be used and what not.
(Given my ignorance in this area, I have decided to learn more about the use of products as they come into my awareness as possible interventions; my primary objective is to provide information for those for whom the use of such products are perceived as acceptable, even necessary. Even though I prefer not to use them I will be attending a workshop to start my education – Mike Viviers and PANAF will be hosting a PSHB/Lipid Workshop on 7th June at 10h30 at Random Harvest. If you would like to attend please contact Mike at growing@rhn.co.za. For directions: https://www.randomharvest.co.za/en-us/Contact.)
While no chemical is registered for tackling PSHB and Fusarium Disease specifically, there are products registered as pesticides for use against other pests or pests in general; these are being experimented with by arborists and others in their efforts to stem the infestation and possible death of trees in their care.
A promising report from a contact is that he used a “pyrethroid and a granular insecticide commonly used for aphids” which “has stopped the spread of PSHB to other limbs in infested trees.” From this person’s perspective “systemic poisons appear to be the best available at the moment.” This then is a registered pesticide for those wishing to tackle the PSHB beetle rather than the fungus.
According to Wikipedia a pyrethroid “is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums. Pyrethroids constitute the majority of commercial household insecticides. In the concentrations used in such products, they may also have insect repellent properties and are generally harmless to humans.”
Pyrethroids are synthetic and more potent that pyrethrin, which is organic. For more information, including possible side effects on this read: https://www.beyondpesticides.org/assets/media/documents/mosquito/documents/SyntheticPyrethroids.pdf
Additional Signs of Hope
Nici Richter from Sustainable Permaculture Solutions, reported seeing a tree in her area fighting back of its own accord, with signs of new life where previously it seemed that the tree had given up.
John Nzira, a permaculturalist with a profound knowledge of Southern African forest ecologies, thinks that we need to accept that many of our urban trees are coming to the end of their lifespan and that the infestation is testament to this fact. A sign of hope is that our indigenous trees appear to be more resilient than the exotics; this suggests that our natural forests may not be affected at all, or at least not as badly as is feared. He agreed to have a look at the FABI list of reproductive and non-reproductive trees to seek out patterns and will hopefully provide guidance on what trees to favour in future tree planting efforts.
In Norwood, the Norwood and Orchards Residents’ Association (NORA) has funded the placement of Wild Olive Trees in pots along the pavements on Grant Avenue. Wild Olives are one of the Big Five carbon sequestration trees for Johannesburg and although on FABI’s list of non-reproductive hosts I am hopeful that young trees such as these will not be infested. The key here, as elsewhere, is careful observation and maintenance.
Transplantation into healthy soil in open spaces at a future date is also something to look forward to; seeing these potted trees for the first time gave me a sense of comfort. If everyone does what they think helps, we increase the chances of transitioning from this period of vulnerability to a more sustainable future with greater confidence and hopefully, with more care and sensitivity for ecological realities.
On a different level, Markus Scheuermaier, from IHlathi Melrose-Birdhaven Conservancy, and JUFA Co-founder, has drawn on existing legislation to protect healthy trees from being felled by developers. Well done to him for his determination to protect our urban trees.
Call to officially declare Johannesburg a Forest
JUFA continues to call for Johannesburg to be formerly proclaimed an Urban Forest. However, John Nzira would like to see it declared a Food Forest.
The latter includes the former, so I am for it being declared a Food Forest; this also potentially dissipates tension between residents who are focused on the need to maintain and create carbon sinks in harmony with nature and those for whom growing nutritious food within the city is a priority. In my opinion there is no reason I can see not to integrate both.
RESOURCES:
FABI Update: https://www.fabinet.up.ac.za/index.php/research/7