4 minute read
Fall armyworm in Western Australia
BY DR HELEN SPAFFORD SENIOR RESEARCH SCIENTIST, DPIRD
The invasive fall armyworm was confirmed in Western Australia on 1 April 2020 from a moth collected in a pheromone trap in Kununurra in March. Eggs and larvae were found in maize in Kununurra on 2 April.
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The subsequent confirmation of moths in Broome, also collected in March, heralded the establishment of fall armyworm in the Kimberley. Detection of the pest in Carnarvon on 29 April however, marked a new stage in fall armyworm’s spread across the State and new host crops. Fall armyworm is known to feed on over 350 different plant species, including many crops. The larvae predominantly feed on crops and pastures from the Poaceae (grass) family, in particular maize, but also sorghum, and forage
FIGURE 1 MAP INDICATING MODELLING OF THE EXPECTED AREAS OF DISTRIBUTION OF FALL ARMYWORM GLOBALLY AND IN AUSTRALIA BASED ON WEATHER CONDITIONS Source: du Plessis, H., van den Berg, J., Kriticos, D.J. & Ota, N. (2017) Spodaptera frugiperda (fall armyworm). Pest Geography. CSIRO-InSTePP, Canberra. Used with Permission grasses. So far, in Western Australia, these are the only crops that fall armyworm has been collected on. But, the pest can also feed on nongrass crops, such as cotton, peanuts, vegetables and some fruit crops. With the latest discovery of fall armyworm in Carnarvon, the DPIRD encouraged growers in the Gascoyne region to actively monitor all horticultural crops, especially sweet corn, tomato and melons. Larvae can reduce the yield of grain, forage and cobs by affecting plant establishment, damaging leaves and attacking cobs.
Spread and establishment
The spread of fall armyworm in Western Australia is unavoidable. In May 2020, the National Management Group agreed with the Consultative Committee on Emergency Plant Pests that fall armyworm is not technically feasible to eradicate. This was due to the pest’s reproductive capacity, ability to fly long distances, wide host range, combined with the remoteness and spread of known infestations (see Figure 1).
Northern Australia’s conditions, including climate and access to suitable hosts, are favourable for fall armyworm to persist year-round. The pest’s migratory ability means it will have little trouble moving from areas where it can survive all year to environments that are suitable for the short-term. In the United States, for example, fall armyworm lives year-round in its native southern Florida, but migrates annually up the east coast into Canada. Fall armyworm can’t survive cold winters or persist when temperatures dip below 10ºC. Nonetheless, the pattern of distribution of fall armyworm overseas does not bode well for the South West and Great Southern regions of Western Australia, where abundant grains and horticultural crops may provide food for the pest during times of the year when temperatures are favourable. Monitoring and trapping of the pest continues as part of DPIRD’s ongoing surveillance program. About 50 pheromone (lure) traps have been deployed throughout northern WA, including Kununurra, Carnarvon, Geraldton and the Pilbara, to determine fall armyworm distribution and assist in providing early warning advice to industry in the regions.
3 FALL armyworm larvae feeding on maize in Kununurra.
3 A fall armyworm larvae causing feeding damage to the leaves of a bean plant.
PHOTO © Scott Stewart, Kansas State University
Management
Fall armyworm is clearly establishing in Western Australia and we are working with growers and stakeholders across the horticulture and grains sectors, in WA and nationally, to understand how to best manage this pest in its new home. The key to effective management is early detection of the pest in the crop and regular monitoring to assess population build up. A significant challenge is that fall armyworm resembles pests already established in Western Australia. Adult moths appear very similar to those of cluster caterpillar, Spodoptera litura, and other armyworms. The larvae have similar markings to bollworms, like Helicoverpa punctigera and H. armigera, and other armyworm. Knowing what to look for, especially for the larvae, is essential for monitoring and managing fall armyworm spread throughout the State and in-crop. To assist growers, DPIRD hosted a webinar conference for over 70 growers, agronomists and industry representatives in the Kimberley on 9 April to discuss how to identify, conduct surveillance, and manage fall armyworm. This was followed by a webinar on 6 May, targeted at a similar audience, and DPIRD development officers in the Gascoyne region, to assist with fall armyworm in Carnarvon, a key horticultural growing area. Although fall armyworm can be a voracious and highly damaging pest in large numbers, low numbers of the insect can be tolerated in most crops. Integrated Pest Management (IPM) that employs a variety of tactics including insecticides will be essential to managing fall armyworm in the longterm. Biological control, host-plant resistance and variations in production practices have been used successfully in other parts of the world and can become part of the fall armyworm management toolbox here in Australia. Insecticide resistance management will be an important element of any IPM program. Fall armyworm also has a history of developing resistance and cross-resistance to several classes of insecticides.
3 DPIRD’S fall armyworm project manager and senior research scientist Helen Spafford and biosecurity officer Tracey Vinnicombe prepare to deploy a fall armyworm pheromone trap in the Kimberley region.
Fall armyworm management has been a challenge worldwide. There is a lot we have to learn about where, when and how this new invasive insect will impact on our production systems. Until we have an understanding of how fall armyworm behaves in Western Australia, it will be difficult to provide comprehensive management recommendations. DPIRD researchers are collaborating to help ensure industry has the best decision making tools and information available.
MORE INFORMATION
Contact Dr Helen Spafford on (08) 9166 4074, email helen.spafford@agric.wa.gov.au, or go to agric.wa.gov.au/plant-biosecurity/fallarmyworm-western-australia.
