YOUR PRODUCTION
Fall armyworm in Western Australia
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BY DR HELEN SPAFFORD SENIOR RESEARCH SCIENTIST, DPIRD
he 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. 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
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WA Grower WINTER 2020
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.
