By: Marianne Coquilleau, Plant Health Australia
Not all pests pose the same risk. Some have the potential to enter Australia unnoticed, establish quickly and cause significant economic damage before they are even detected.
These are known as High Priority Pests (HPPs). Understanding which exotic pests pose the greatest risk helps industry and government prioritise and implement preparedness activities.
As part of the Biosecurity Plan for the Australian Grain Industry, a list of HPPs was compiled based on their overall risk across four key risk categories:
These risks are assessed for each individual pest and are rated as either negligible, low, medium, high or extreme. Only those pests with a high rating across the majority of these risk categories qualify as a potential HPP.
Entry potential
Australia’s island geography provides some natural protection from exotic pests, supported by strict pre-border and at-border policies, procedures and legislation that significantly reduce entry potential for most exotic pests.
Pests are more likely to enter Australia if they can survive on multiple host materials or hitchhike on common long-haul cargo pathways.
Khapra beetle (Trogoderma granarium) is a well-known example. Ranked second on Australia’s National Priority Plant Pest list, it is a serious pest of stored grains. Its larvae feed on a wide range of seeds, grains and dried produce, contaminating them with skins and moults and rendering them unfit for consumption.
Khapra beetle can also hide in hard-to-detect areas, including beneath the flooring of sea containers, and survive for months without food or water. Once suitable food sources are available again, khapra beetles quickly become active. Common commodities such as grains, rice, nuts and other plant-based products are particularly at risk.
For this reason, Australia has strict import requirements that regulate which goods can enter the country and under what conditions[1]. For khapra beetle, certain high-risk goods from countries where the pest is established are prohibited, while others must be treated or accompanied by a phytosanitary certificate in line with Department of Agriculture, Fisheries and Forestry requirements[2].
Establishment potential
Biosecurity does not stop at Australia’s international border. Multiple systems are in place to detect exotic pests should they enter and reduce the likelihood of establishment. These include treating goods, monitoring high-risk zones like ports and storage warehouses, and maintaining good site hygiene.
Quarantine procedures and good farm hygiene in cropping and grain storage areas help limit the establishment and spread of pests and diseases that we already have in the country, allowing time for accurate identification and effective control measures to be put in place. These are equally effective for exotic pests and diseases.
HPPs can consist of pathotypes or exotic variants of species already present in Australia. One example is Ug99, a particularly virulent lineage of the wheat stem rust pathogen (Puccinia graminis f. sp. tritici) that has emerged overseas. There is a greater risk of Ug99 becoming established in Australia if it enters and is mistaken for an endemic strain, not reported and subsequently not treated adequately. Around 30% of current wheat varieties in Australia are expected to show some susceptibility to this specific strain. We should always remember to report strange or unusual symptoms, especially if they occur on a variety that should be resistant, or on an unexpected host plant.
Spread potential
HPPs also rate highly in their ability to rapidly spread into new areas. Pests with a high spread potential are often characterised by their ability to fly long distances, spread through natural pathways such as wind and water, or hitchhike on potential carrier or risk material through human-assisted movement. Hitchhiker pests can often be moved in carrier material such as soil, crop debris and other organic material or inadvertently stuck on shoes or vehicle wheels. In the case of fungal diseases, their spores can be deposited and transported on items of clothing, gardening tools and equipment.
Exotic viruses like the Groundnut bud necrosis virus (GBNV) and Maize chlorotic mottle virus (MCMV) can be transmitted through infected plant material and by several thrips species already present in Australia that are known to vector these viruses. For Maize dwarf mosaic virus (MDMV), known vectors include many different aphid species such as Green peach aphid (Myzus persicae), a common agricultural pest in Australia. Although these viruses are not present in Australia, their potential to spread is considered high due to the presence of established insect vectors.
Restricting external vehicle access to production zones on-farm, thoroughly cleaning machinery and equipment and controlling weeds can all help mitigate the risks of spreading infected plant material or the vectors that could be spreading these kinds of viruses.
Economic impact potential
The final and most critical risk category for growers is potential economic impact, including effects on yield, farm profitability and the broader grains industry. All HPPs identified in the Biosecurity Plan have been assessed as likely to cause significant impact, based on overseas experience, increased control costs and potential loss of access to premium markets. Detection of any of these pests in Australia could also lead to trade disruptions, with international partners pausing imports until eradication or proof of freedom is achieved.
Karnal bunt (Tilletia indica) is one such pest and its economic impact is ranked as extreme. This fungal disease partially infects wheat spikes, making it hard to notice in the crop. Rather than heavily reducing yield, contamination levels of as little as 3% in wheat consignments are enough to render them unfit for human consumption. It has been estimated that if karnal bunt were to be introduced to Australia, we could suffer losses of 8 to 25% in wheat exports and experience market access restrictions to 77 wheat trading countries[3].
Keeping HPPs out
HPPs can enter and spread without being immediately detected, making surveillance, awareness and early reporting critical. Therefore, the effectiveness of our national biosecurity system relies not only on the diligence and vigilance of biosecurity personnel employed by state and Commonwealth agencies nationwide, but also on the collaborative engagement of industry, producers and the wider community. Decisions made on farms, in storage facilities and along supply chains can be pivotal in identifying threats that slip through traditional channels.
Growers and the community are a critical line of defence, and understanding HPPs helps turn awareness into action. Often, the difference between a near miss and a national impact comes down to someone noticing something unusual and reporting it.
If you notice anything unusual like new symptoms, unfamiliar pests or unexpected damage, report it immediately. Report suspected exotic plant pests to the Exotic Plant Pest Hotline: 1800 084 881.
One report could protect an entire industry.
For more information, download the High Priority Pests for the Grains Industry factsheet to stay informed and help protect our grains industry.
The Grains Farm Biosecurity Program is an initiative to improve the management of, and preparedness for, biosecurity risks in the grains industry at both farm and industry levels.
Launched in 2007, it is managed by Plant Health Australia (PHA) and funded by growers through Grain Producers Australia (GPA), in partnership with the governments of New South Wales, Queensland, South Australia, Victoria and Western Australia.
References
[1] Biosecurity (Conditionally Non-prohibited Goods) Determination 2021 – Federal Register of Legislation
[2] List of target risk countries for host of khapra beetle
[3] Bishnoi, S.K., He, X., Phuke R.M., Kashyap, P.L., Alakonya, A., Chhokar, V., Singh, R.P. & Singh, P.K. (2020). Karnal Bunt: A Re-Emerging Old Foe of Wheat. Frontiers in Plant Science. 11(569057), DOI:10.3389/fpls.2020.569057.