Another wasp is making waves in South Africa’s macadamia industry, this time a natural predator of the felted coccid, which has arrived in the country and is under quarantine readying for release.
The dominant regular predator of Australia’s naturally occurring felted coccid – now a significant pest in South Africa’s macadamia orchards – has arrived in the country and is being readied for battle in quarantine facilities at the University of Pretoria.
Entomologist Anthony King from the Agriculture Research Council, Plant Protection Research Institute, Roodepoort, travelled to Hawaii in July last year to collect three “little containers” carrying 59 wasps to start a captive breeding programme, now at an advanced stage with populations almost ready for release.
As in South Africa, the felted coccid (Acanthococcus ironsidei) is a problem pest in the macadamia orchards of Hawaii. The wasp was successfully introduced there in 2013, becoming an integral part of the island industry’s integrated pest management strategy. That work is now providing a base from which South African scientists can ready the predator for release into local orchards.
Scientists anticipate the introduction of the predatory wasps will make a valuable contribution to sustainably managing felted coccid infestations in the domestic macadamia sector.
Acanthococcus ironsidei is a very tiny sap-sucking insect host-specific to the macadamia. It has a short life cycle, meaning overlapping generations can be present in the orchards throughout a season. The pest causes branch and tree die-back, and while it doesn’t affect the quality of the nuts, it does reduce yield and infected trees need time to recover from infestation.
Speaking at SAMAC’s recent annual industry conference in KwaZulu-Natal, King said surveys carried out by the Hawaiian Department of Agriculture in 2013 had identified a species of wasp – Metaphycus macadamiae – which was found to be the dominant natural enemy of the macadamia felted coccid in Australia.
The female of the little dun-coloured wasp feeds on the felted coccid nymphs and lays her eggs in maturing females. The developing young then feed on the felted coccid female, killing it from the inside.
“In Australia, the macadamia felted coccid is considered a relatively minor pest that seldom requires active management. This is because the insect is suppressed by a suite of indigenous natural enemies, which maintain adequate control under most circumstances,” King said.
Explaining the protocol linked to the importation of the wasp into an “invaded” country, he said after the field surveys, the insect is quarantined and studied to make sure it has the necessary biological attributes before being exported. “Then that species has to undergo host specificity testing to make sure it doesn’t become a pest itself. Once that testing is complete you submit an application for release to the appropriate authorities,” he said.
Since its arrival, Metaphycus macadamiae has settled in well. The first objective of the project to establish a “culture” of the wasp has been completed, and host specificity testing on indigenous and economically important scale species that might be present in South Africa is under way.
“The first generation of South African-born wasps emerged in September 2024 with at least 11 generations, probably more, emerging since then. We have really concentrated on stabilising the population and growing the number of wasps in our quarantine facility while implementing the lessons we learned in Hawaii,” King said.
About 36 local scale species have been targeted for host specificity testing. These were prioritised based on their phylogenetic (evolutionary relationship) distance from the macadamia felted coccid.
King said two out of the 36 identified species from two different scale families, namely Diaspidiotus mesembryanthemae and Pulvinaria delottoi, were tested, with zero emergence where Metaphycus was introduced versus 32 individuals emerging from the control. “This is a good start and what it means for the industry is that a successful biological control programme will reduce the current over-reliance on insecticides for the control of Metaphycus macadamiae, and lessen non-target impact on existing natural enemies and pollinators in the orchards,” he said.
SAMAC has assisted with funding and support for the programme, with local macadamia growers helping with field work and the collection of infested material in their orchards.
King also thanked the authorities in Hawaii for their technical assistance and a supply of the insects for export to South Africa.
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Colleen Dardagan
