A team of predatory insects has been released in Sydney’s Centennial Park to manage a fairly heavy aphid infestation in its century-old rose garden, according to senior horticulturalist Tristan Harman.
Centennial Park’s rose garden, established in 1909, is home to about 800 rose plants of 33 varieties. Senior horticulturalist from Western Sydney Parklands, Tristan Harman, said the garden had a fairly heavy aphid infestation after the roses were pruned in winter.
"If these aphids were just left to do their business, the roses wouldn't be roses anymore," Mr Harman said.
To control the pests, thousands of parasitic wasps and about 1,000 ladybirds were released into the garden. The adult parasitic wasps lay eggs inside aphids, and the hatching wasps eat the aphid from the inside out, Mr Harman explained. The ladybirds eat the aphids directly.
The insects are released in five batches from September to early November. This is the second time Mr Harman has been in charge of the releases. The insects cost about $1,300 this year, supplied by a South Australian company in cooled containers.
Mr Harman said using predatory insects seemed like “black magic” when he studied almost 30 years ago, but it later became common. An integrated pest management plan was chosen rather than spraying chemicals for every possible pest or disease; he said some chemicals are toxic to bees and can kill things they are not trying to kill.
"It feels great," he said.
The park hosts about 17 million visitors each year, including people attending weddings, and Mr Harman said the team tries to keep the garden at its highest standard without spraying unless absolutely necessary.
Analysis
Why This Matters
- The use of predatory insects reduces the environmental impact of pest control, protecting bee populations and other beneficial insects.
- The successful program in a high-profile public garden may encourage other councils and parks to adopt biological alternatives.
- The approach is cost-comparable to chemical sprays while avoiding harm to non-target species.
Background
Centennial Park was originally a swamp that became a drinking water source before being transformed into parklands, opening to the public in 1888. The rose garden was established in 1909 by Joseph Maiden, the then-park director. Today it features 33 rose varieties with about 800 plants.
Aphids are small, sap-sucking insects that can cause roses to become distorted and puckered, and can spread viruses between plants. They also encourage black mould.
What to Watch
- Whether the program will be expanded to other parts of the park or other green spaces in Sydney.
- The long-term effectiveness of the insect releases in maintaining aphid control.
- Potential for other councils to adopt similar integrated pest management plans.
Checked
12 claims in this story checked against 1 source: 12 supported.
Show each claim
- SupportedParasitic wasps and ladybirds have been deployed to protect Sydney’s historic rose garden.Just In: “A team of ladybirds and parasitic wasps, led by Western Sydney Parklands senior horticulturalist Tristan Harman, have been tasked with managing "a fairly heavy aphid infestation".”
- SupportedBiological pest control was chosen rather than spraying for every possible pest or disease.Just In: “"It was decided that it's obviously better to use an integrated pest management plan rather than just spraying with toxic chemicals for every possible pest disease," he said.”
- SupportedA team of predatory insects was released in Centennial Park to manage a fairly heavy aphid infestation, according to Tristan Harman.Just In: “A team of ladybirds and parasitic wasps, led by Western Sydney Parklands senior horticulturalist Tristan Harman, have been tasked with managing "a fairly heavy aphid infestation".”
- SupportedThe rose garden was established in 1909 and has about 800 plants of 33 varieties.Just In: “Today, it is home to 33 different varieties of roses, with an estimated 800 plants overlooking Busbys Pond. [...] Centennial Park's popular rose garden was established in 1909.”
- SupportedHarman said, “If these aphids were just left to do their business, the roses wouldn't be roses anymore.”Just In: “"If these aphids were just left to do their business, the roses wouldn't be roses anymore," he said.”
- SupportedThousands of parasitic wasps and about 1,000 ladybirds were released into the garden.Just In: “Thousands of parasitic wasps and their eggs have been released into the garden. [...] About 1,000 ladybirds, otherwise known as ladybugs, are far tamer in comparison and easier to spot, eating the aphids as they appear.”
- SupportedAdult parasitic wasps lay eggs inside aphids, and the wasps eat the aphid from the inside out after the egg hatches.Just In: “"The adult lays its eggs inside the body of the aphid and the egg hatches within the body, then [the wasp] eats the aphid from the inside out," he said.”
- SupportedThe insects are released in five batches from September to early November.Just In: “Five batches are distributed among the garden beds from September to early November: two in the first fortnight, then every fortnight after.”
- SupportedThis is the second time Harman has been in charge of the releases.Just In: “The insects are released annually, and this is the second time Mr Harman has been in charge.”
- SupportedThe insects cost about $1,300 this year and were supplied by a South Australian company in cooled containers.Just In: “The ladybirds and three types of parasitic wasps, including their eggs, were supplied and sent to Sydney by a company based in South Australia. [...] Mr Harman said this year's batch cost about $1,300”
- SupportedHarman said using predatory insects seemed like “black magic” when he studied almost 30 years ago, but later became common.Just In: “Mr Harman said when he was studying almost 30 years ago, using predatory insects to deal with pests seemed like "some sort of black magic". [...] after, 15, 20 years, it was something that was common”
- SupportedHarman said some chemicals are toxic to bees and can kill things they are not intended to kill.Just In: “"I think it would probably work out comparable in the overall growing season to be releasing these insects, especially when you think of some of the chemicals you can use that are toxic to bees," he said. "If you're spraying chemicals to kill aphids, you'll kill things you're not trying to kill."”
