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https://theconversation.com/fungi-to-the-rescue-south-african-scientists-use-innovative-approach-to-protect-apple-trees-236886>
"Gardeners the world over dread the appearance of aphids on their plants. There
are around 4,000 species of these sap-sucking insects and about 250 are pests
that can wreak havoc on crops in a garden or orchard.
One of them is the woolly apple aphid (Eriosoma lanigerum). As its name
suggests, this aphid attacks apple trees and is recognisable by the white, waxy
excretions that cover and protect the insects.
The aphid is native to the US and can be found throughout the world wherever
apples are cultivated. It was first identified in South Africa in 1895 and has,
over time, become a serious pest of apples.
The aphids infest apple trees through the plants’ root systems and above-ground
growth. The colonies cause abnormally large swellings on apple roots, impeding
the flow of nutrients and water throughout the plant. If the infestation is not
controlled, a tree’s buds, shoots and fruit-bearing wood can be entirely
destroyed. The mother insect on the roots produces live young called crawlers,
which migrate from the roots to above-ground parts of the apple tree. Young
trees and new cultivars of apples are especially vulnerable.
In 2023, South Africa produced 1.3 million tonnes of apples, with 544,759
tonnes exported. Apple cultivation covers over 25,000 hectares; the primary
growing area of 15,000 hectares is located in the Western Cape province,
particularly in the Ceres and Groenland regions. The estimated value of apple
production in 2023 was R8,794 (about US$490) per tonne.
The most common method of controlling woolly apple aphid infestations in
orchards has, for the past several decades, involved applying high doses of
chemical insecticides. Many apple growers globally, including South African
producers, have reported that the insects seem to have become resistant to
these insecticides. This, along with concerns about the harmful effects of
chemicals on the environment, has led scientists to look for new insect control
methods.
We are biologists at Stellenbosch University’s Department of Conservation
Ecology and Entomology, conducting research on insect-killing fungi and
nematodes to control pest insects. In a recent academic article we examined
whether entomopathogenic fungi could help to keep South Africa’s apple trees
safe from woolly apple aphid. These fungi are naturally found in all soils in
low numbers, where they keep insect populations under control.
We wanted to know whether the fungi could be used for biocontrol, an approach
that involves using living organisms to control pests. The results were clear:
three of the six fungi species we tested were extremely fast and effective at
infecting and destroying woolly apple aphids."
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
