Victorian growers may have a new weapon in the fight against fruit fliesPest and Disease Management
The full version of this article will be published in the AFG Winter 2022 edition.
Parasitoid wasps have the potential to provide apple and pear growers with an effective biocontrol to help sustainably manage fruit fly populations.
That’s according to a two-year project, led by Agriculture Victoria, which has demonstrated that populations of parasitoid wasps can be established in Victoria, at least for the duration of a season.
As populations of Queensland fruit fly (QFly) continue to escalate in Victoria, this will be welcome news for growers in the region, where parasitoid wasps, a natural enemy of QFly have been largely absent.
The project focused on two parasitoid wasp species which both already exist in Australia and prey exclusively on fruit flies – Fopius arisanus and Diachasmimorpha kraussii.
Just a few millimetres long and looking like tiny, winged ants with long antennae, they have an acute sense of smell. They attack QFly by laying eggs either directly into the QFly’s eggs or into developing larvae.
Researchers from Queensland University of Technology collected populations of both arisanus and kraussii species from the wild, and having established them in culture, sent them down to Agriculture Victoria’s Tatura SmartFarm where they were mass reared in their thousands.
The research was successful.
Arisanus populations were able to persist in the environment for several weeks, actively parasitising Qfly. Parisitoids are still emerging from fruit collected at two of the five sites where we monitored up to 17 weeks post release. This is really encouraging and is evidence that the parasitoids can establish at least for the duration of the season.
Kraussii is also demonstrating good dispersal; Fruit has been collected which contains parasitized larvae up to 1.5km away from a release site.
Research is now underway to look at the overwintering behaviour of parasitoid wasps in Victoria and Southern Australia.
Dr Paul Cunningham, the lead researcher for the project said more research was needed to investigate whether on-farm releases of large numbers of parasitoid wasps would benefit growers in fruit fly management in a cost: benefit sense.
“We have shown in the apple and pear orchard that when you release the arisanus, they get to work straight away,” Dr Cunningham said.
“Growers are often interested in whether they will be able to commercially buy these parasitoids and release them. It’s certainly a possibility in the future, but we need to evaluate their effectiveness properly for the growers – we don’t want to be proposing that something is going to work and be cost effective, if it’s actually too expensive and they won’t get enough benefit from it.
“That’s an important question we hope to address in another phase of the work.
Although much more work is required to determine the feasibility of commercial applications of parisitoid wasps on apple and pear orchards, there are still significant benefits that orchardists can reap from exploring those biological controls which are available today as part of a pest management strategy.
Biological control, often considered as part of an Integrated Pest Management strategy, provides better production, plant health and human health outcomes for orchards. Importantly, using biological agents means apple and pear growers can use less insecticides reducing input costs as well as reduced exposure to chemicals.
Want to learn more about how IPM can have success in orchards, check out this webinar hosted by Angelica Cameron, entomologist and IPM specialist at Bugs for Bugs and growers Jason Shields from Plunkett and Brent Reeve from Jefthomson (Watch Here: Pear Masterclass 2021)
‘Parasitoids for the management of fruit flies in Australia’ is a nationwide collaboration funded by the Department of Agriculture, Water and Resources, and Hort Innovation, using the apple and pear, citrus, rubus, strawberry, summerfruit, table grape and vegetable levies, co-investment from state governments, and Australian horticultural industries.