Indigenous Nursery News Blog

Polyphagous Shothole Borer Beetle (PSHB) Control Update

Lipids, together with knowledge of the life habits of the Polyphagous Shothole Borer (PSHB) have been shown to possibly be the best defence against this scourge, which is lined up for an ecological fire storm. Our Government is ominously quiet about the severity of not only the current infestation, but the looming ecological, tourism and societal implications.

Treating trees infested with PSHB

Mike Viviers of Random Harvest Indigenous Nursery has been treating and observing PSHB for some time (about 18 months) on an experimental level, but armed with knowledge gained in this time of the life habits of the borer beetle and PANAF 6, he has begun to treat trees all over Johannesburg suburbs.

Mike is spraying only the fungicidal PANAF 6. It is environmentally friendly and harmless to the point where you can treat your athletes foot with it. Certainly an ecologically better option than KOHINOR 350 INSECTICIDE or TEMIK 150G and some of the systemic fungicides being sprayed everywhere. These harmful chemicals are perhaps understandable in this dire situation, but ecologically indefensible.

Winter cold temperatures help to control PSHB

Johannesburg temperatures are now dipping below 12 degrees Celsius for parts of the day, and literature states that the beetles stop taking flight below 12 degrees Celsius. The argument runs along the following lines: Spray PANAF 6, kill the Fusarium euwallaceae fungus by drying it out and therefore deprive the Euwallacea whitfordiodendron (PSHB) of their food – and they will die of the hunger or in the case of the grubs, immaturity and lack of food.

When Viviers sprayed a double story Platanus (London Plane) tree with PANAF 6, the following observations were made. Within 12-15 hours the entire trunk was swarming with grubs and beetles. The grubs fell to the ground and died, the flightless males could not reach new sources of food so also died, unfertilised females (cannot multiply because they need to be fertilised by the males in the tree) and it is believed (according to literature) that fertilised females did not take flight as temperatures were below 120C.

Mike is currently conducting experiments to determine whether Panaf 6 sterilises the Fusarium spores on the beetle as well, or not.

Beetles can burrow quite deep – up to 50cm in some of the trees we have measured. However, it also appears that the fungus concentrates in a 3-6 cm ring immediately below the bark. Certainly seems not to colonise the xylem – perhaps the wastelands of the tree as far as food is concerned. The photograph is of a felled, dead oak tree. I guess 3-5 years since infestation. If the Fusarium did not spread to the xylem in this period, I think it is safe to say that it grows in the nutrient rich cambium and phloem areas.” Mike says.

The cambium and phloem “ring” however stretches from the roots to the very crown. Laboratory experimentation revealed that PANAF 6 can penetrate up to 10cm deep – this is well beyond the visible Fusarium line. Thus the only thing to ensure your tree is safe is to get enough PANAF 6 into your tree to be transported into the crown of the tree. If you can reach the crown of your tree that is a bonus and faster than stem applications. Mike stresses though, that both methods are effective.

Another very worrying observation is that it would appear that the PSHB has largely denuded it source of “favourite” trees in Johannesburg. These would be Platanus (Plane), Acer, Fraxinus and Liquid Amber. Mike has been looking at uninfected trees for the past 18 months in every garden he has sprayed, with a view to get a “PSHB resistant” plant list. Jacaranda, which literature lists as a “Breeder/Nursery” tree has escaped so far. In the past month the following trees, PSHB free up to now, have been added as victims.

  • Jacaranda mimosifolia
  • Yucca sp.
  • Boscia albitrunca
  • Ligustrum lucidum
  • Lagerstroemia indica
  • Tipuani tipu
  • Melia azedarach
  • Eriobotrya japonica

These might just be chance “hits”, but it might also be the second wave of the PSHB infestation. Time and observation will tell

Take action against invasive PSHB Beetle

Contact Mike Viviers for advice on affordable control of PSHB or spraying of your trees on 082 721 2478 or email us.

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