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Infecting aphids with a specific type of bacteria could help control these garden and agricultural pests in a more sustainable and environmentally friendly way.
As well as being a backyard nuisance, aphids are globally important agricultural pests causing expensive losses in yield and quality in many Australian food crops. Unfortunately, many aphid species are resistant to pesticides, making control ineffective, costly, and harmful to the environment.
New research published in PNAS aims to develop new tools to tackle this problem in a way that is both sustainable and environmentally friendly. The research was led by Dr Xinyue Gu, Dr Perran Ross and Professor Ary Hoffmann with Australian and international collaborators.
The solution lies in the microbial world – specifically, bacteria that can influence insect reproduction called endosymbionts.
The main target of the study was the green peach aphid (Myzus persicae), one of the most economically important crop pests globally. Researchers transferred one type of bacteria called Rickettsiella from a different aphid species to the green peach aphid through a technique called microinjection.
Rickettsiella caused the aphids to change colour, as well as cutting their reproduction and lifespan by half. Aphids that carry Rickettsiella were found to pass the bacteria not only to their own offspring but also to other aphids that are feeding on the same plant.
This continuous spread of Rickettsiella allows it to quickly invade aphid populations and at the same time, reduce their ability to multiply and spread.
The new study suggests that naturally sourced bacteria from other species, such as Rickettsiella being transferred from pea aphids to green peach aphids, could be used to suppress aphid populations and reduce the damage they do to vital agriculture and horticulture industries.
Interestingly, the negative impact of Rickettsiella on aphid reproduction was also found to increase with temperature. Introducing Rickettsiella-carrying aphids during the initial stages of crop growth may result in swift transmission of infection among the aphid population, followed by a decrease in multiplication as temperatures rise, leading to an effective population crash before they have had time to cause economic damage.
The team previously pioneered similar approaches to control mosquito populations and the spread of dengue fever. They now hope that releasing aphids carrying bacteria like Rickettsiella could be an effective tool for aphid management.
Adopting management tactics based on endosymbionts could have novel and lasting effects on the population dynamics of aphids, leading to improved crop yields and a reduction of plant virus transmission.
The researchers are now progressing to larger-scale trials where they will release aphids into greenhouse environments. These experiments will test the ability of endosymbionts to spread under more natural conditions, assess their impact on the aphid populations and monitor the impact on plant damage.
Before any field releases take place, the researchers will undertake thorough risk assessments including measuring impacts of endosymbionts on plant viruses, interactions with natural predators and potential transmission of endosymbionts to other organisms. The team is also exploring the use of endosymbionts to control other aphid pest species.
This work was undertaken as part of the Australian Grains Pest Innovation Program (AGPIP), supported through funding provided by the Grains Research and Development Corporation (UOM1905-002RTX) and The University of Melbourne, as well as a research grant from VILLUM FONDEN (40841).
Grains Research and Development Corporation grant (UOM1905-002RTX) to Ary Hoffmann, Paul Umina and Perran Ross
Research grant from VILLUM FONDEN (40841) to Ary Hoffmann
Gu, Xinyue et al (2023) A rapidly spreading deleterious aphid endosymbiont that uses horizontal as well as vertical transmission. PNAS, 120 (18) e2217278120 https://doi.org/10.1073/pnas.2217278120
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First published on 26 May 2023.
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