Hortgro’s long-serving crop protection programme manager started his career with the inception of integrated pest management in South African orchards. By Anna Mouton.

Although he was born in Johannesburg, Matthew Addison has deeper roots in the deciduous fruit industry than one might imagine. His father, a chemical engineer, was involved in the design of the original Appletiser plant for Edmond Lombardi. His family moved to the Natal Midlands while Addison was in school. He graduated with a BSc in botany and entomology from what is now the University of KwaZulu-Natal. “I then had the choice of either the military or a master’s — there was a bursary for a master’s in forest entomology,” he remembers. Unfortunately, Addison was called up after submitting his thesis but before he could make the required corrections. “So, I didn’t have time to rewrite any of it,” he says. “And when I came out of the military, my mother handed me a letter from the Head of Department at the University.”

The three-month-old letter informed Addison that the South African Apple and Pear Producers’ Organisation — the forerunner of Hortgro Pome — wanted a young entomologist to start an integrated pest management programme. “I phoned — we were still on a wind-up exchange — and spoke to Richard Hurndall, who said I could come to see them,” says Addison. At the beginning of 1987, he was interviewed at what is now the ARC Infruitec-Nietvoorbij. “The panel was Richard, Peter Dall, and Bernard Treptow,” relates Addison. “Bernard was head of technical services at Kromco and became one of my mentors.” The interview was a success — Addison started work on 15 February 1987.

The dawn of integrated pest management

“I packed all my stuff into a little 1200 Datsun bakkie and drove down to the Cape,” says Addison. “Integrated pest management had begun that season, and I took over the database.” He was based in an office next to the maturity indexing laboratory in Elgin and collected monitoring data for all the principal pests from all the main production areas, which he presented to the integrated pest management group every second Wednesday in what is now the Department of Conservation Ecology and Entomology’s tea room.

The meetings were chaired by Buks Nel, one of the early advocates for integrated pest management. Addison recalls some heated discussions. “We were in the midst of a mite crisis, and Ken Pringle said this is because growers are spraying so many synthetic pyrethroids. Ken had done more than ten years of work on biological control of mites and was warning about over-spraying and resistance.”

Pesticide resistance was a significant driver of the initial impetus for integrated pest management in the pome-fruit industry. Addison and Kromco technical adviser Frikkie van Schalkwyk’s attendance at an integrated pest management course at the University of California, Davis, in 1990 was a turning point. “All the big names were there,” says Addison. “And part of that trip included visiting Oregon State University, where I had discussions with Helmut Riedl, who was working on codling moth. I wanted to know about codling moth because we were having issues with control.”

Addison suspected that codling-moth control was failing due to pesticide resistance. His monitoring data included orchards that suffered 25% damage despite 14 applications of azinphos-methyl. This was before the advent of pheromone disruption and further motivation for a new approach to pest control.

Unifruco and the serendipitous mite

In 1989, Unifruco Research Services was established to provide research support to the deciduous fruit industry, and Addison relocated to Stellenbosch. Around this time, Pringle persuaded the pome fruit industry to import a predatory mite and employ an American entomologist to breed it locally for mite biocontrol. “What was instrumental was that the American said he needed two technicians,” says Addison. “So, we employed Joyene Isaacs and Roberta Burgess, and the three of us had a lot of fun, collected huge amounts of data and concluded this predatory mite didn’t work.”

Isaacs became the head of the Western Cape Department of Agriculture and currently chairs the Agricultural Research Council. Burgess is the senior manager of the Research and Technology Development Services Programme in the Northern Cape Department of Agriculture, Environmental Affairs, Rural Development and Land Reform.

Meanwhile, the crop-protection industry imported a second predatory mite, which they hoped to commercialise. Serendipitously, the culture was contaminated with Neoseiulus (Typhlodromus) californicus. “Suddenly, in Elgin, we started picking up this mite that wasn’t one we’d released,” says Addison. “It spread like wildfire and did a great job, so it was an accidental release of a biocontrol agent that worked well.”

Sterile fruit flies and codling moths

The deregulation of the fruit industry in 1997 saw the Deciduous Fruit Producers’ Trust — which became Hortgro in 2013 — replace Unifruco. Addison continued researching resistance in codling moth, collaborating with Riedl, and eventually spending a year at Oregon State University. When he returned, his laboratory had been dismantled to make space for the new Deciduous Fruit Producers’ Trust management, including the newly appointed manager, Hugh Campbell. Although the transition period was disruptive and funding was scarce, two notable advances in integrated pest management occurred — pheromone disruption and sterile insect technique. “The whole industry adopted pheromone disruption for codling moth almost simultaneously,” says Addison. “There was money for sterile fruit flies and false codling moth, and I said, what about codling moth?”

With the support of Campbell and the technical skills of Dalene Stenekamp, Addison cultured and irradiated codling moths. This led to the establishment of the insectary at Welgevallen, which now forms part of PHYLA, the pome- and stone-fruit industry’s bespoke phytosanitary research facility. The sterile insect technique for fruit flies and false codling moths is now well-established, but the codling-moth project was eventually shut down due to cost concerns and limited uptake. Addison thinks this was short-sighted. “There are gaps in mating disruption in some orchards,” he notes. “With steriles, you could suppress the moths to very low levels.”

Pest control today and tomorrow

Addison moved to an office in the Department of Conservation Ecology and Entomology at Stellenbosch University in 2000 and became more involved in teaching. “It has been fun to see the people coming through the University system,” he says. “We’ve put through many students, and it’s been the best experience of my life.”

He has mixed feelings about the status of crop protection. “Is our pest control as integrated as it could be? No. Are we chemically dependent? Yes. We have reasonable control of our pests, but are at risk.” Biocontrol is an area where Addison thinks more needs to be done, and he still believes that sterile codling moths are a missed opportunity. Pheromone disruption has been a game-changer but driven mainly by the crop-protection industry.

Addison retired as the Hortgro crop protection programme manager on 30 September 2024 and will continue on a contract basis at Hortgro Science as a crop protection researcher. While his appointment was originally motivated by concerns about resistance, the need for integrated pest management has only grown over the past nearly four decades. “Things have changed. There’s much more external pressure on the industry,” reflects Addison, “And there will be considerably more over the next ten years, especially with trying to control invasive pests.”