GEORGE NEWS - The challenge of the PSHB (Polyphagous Shot Hole Borer) infestation is escalating. This is how Dr Jaap Steenkamp, a well-known forestry specialist, commented about the PHSB, which has been wreaking havoc on trees in George and surrounds for more than two years.
He said large numbers of tree owners started making inquiries in January to report new activity of insects.
"The reason for this is simply that the systemic treatment came to the end of the effective prevention period. It must be assumed at this stage, if time of treatment is carefully determined, that we can preserve our trees through an annual treatment."
He stressed that PSHB is not a seasonal problem. "Scientists allege that activity only slows down if temperatures drop below 16°C. Personally I believe the problem does slow down in the winter months simply because most trees will enter a phase of rest with significantly less sap flow in the tree. This should influence the insects," he said.
"The highest activity is observed from October to February. The best time for treatment is early in the growing season, being September to October, and it is efficient until end of April. From May to September, surface spray with the appropriate organic chemicals is advisable."
Steenkamp said various companies are involved in tree treatment. "We do treat significant numbers of trees with good results. The trees severely affected include (but are not limited to) oaks, liquidambars, planes and alders. Fruit trees, including nuts and avos, are very susceptible to the insect (borer). When a tree is treated with systemic insecticide, the waiting period before fruit can be consumed is 200 days."
The oak trees seem to be the biggest problem and early detection or even preventive treatment for oaks is critical. "I doubt if there is a single oak in George that is not infected."
Steenkamp stressed that this is a constant and long-term battle that will have to be fought for a number of years. After some trees develop resistance that enables them to survive, the current general species composition will change and the treatment can be relaxed. "We will be able to control the problem, but not to eradicate it," he said.
Asked about the impact of the Covid-19 lockdown, he said that treatment almost came to a complete standstill from March to October 2020. "After that we experienced a slow recovery of the situation."
The entire George area is affected and there are also numerous infections in Plettenberg Bay and Knysna. He advises people to observe their trees and decide whether to treat or not.
"Please keep your trees in good condition by providing the required water and food to the tree."