Fall armyworm

Fall armyworm is an invasive pest, which has been reported to feed on more than 350 plant species, and impacts economically important cultivated grasses such as maize, rice, sorghum, sugarcane and wheat, as well as fruit, vegetable and cotton crops.

Fall armyworm is native to tropical and subtropical regions of the Americas, and since 2016 has spread to Africa, the Indian subcontinent, China and South East Asia.

Adult moths are highly mobile and can fly long distances with suitable weather conditions. This pest is also prolific, reproducing at a rate of several generations per year.

The larvae can attack leaves, shoots, stems and fruit. Plants of different ages, from seedlings to mature plants, can be affected.

Australia’s climate and the production of suitable hosts are favourable for fall armyworm to establish and spread. Australia’s environment and native flora may also be impacted.

The adult moths are capable of flying long distances aided by wind currents.  All life stages can be moved on infested plant material.

Adult moths are nocturnal and are most active during warm, humid evenings.

Fall armyworm larvae are most active during late summer and early autumn months, however they can be active year-round in tropical areas.

Fall armyworm is most likely found in warm, moist regions with little forest cover.

Depending on the plant, fall armyworm can cause significant and sudden crop damage and collapse if left unchecked.

Symptoms of fall armyworm include leaf damage such as pinholes, windowing, tattered leaf margins and defoliation of plants.

Growers should also look out for tiny larvae, less than 1 mm, that are more active at night, eating pin holes and transparent windows in leaves and bigger larvae grazing on leaves, stems and fruit, and leaving behind insect excrement.

In grass-like plants, larvae are often in plant whorls where leaves branch from the stalk.

Fall armyworm can be confused with a number of armyworm species that are present in Australia, however fall armyworm is very different in terms of its impacts.

Distinguishing fall armyworm from similar looking moths or caterpillars requires specialist diagnosis. Common armyworm species include: Mythimna convecta (common armyworm), Mythimna separata (northern armyworm), Spodoptera exempta (dayfeeding armyworm) and Spodoptera mauritia (lawn armyworm).

More information about these species is available at: https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/crop-growing/pests-field-crops/armyworm

Fall armyworm was first detected on two Torres Strait islands in January 2020. The first mainland detection in Australia was at Bamaga in February 2020.

Subsequent detections of fall armyworm were on a property in the Gulf country of north-western Queensland, and in South Johnstone, Tolga and Lakeland in North Queensland.

Recent detections have been at the Burdekin area, near Bowen, and Bundaberg.

No other countries have tried to eradicate fall armyworm. Given how quickly the pest moves, most countries have had little time to respond, and they have moved quickly to pest management.

In well-managed crops, there has been reasonable success using chemical treatment. More work will be undertaken to provide industry with appropriate recommendations for control of the pest.

Fall armyworm represents a new biosecurity threat for Queensland (and Australia).

It is not currently listed as prohibited or restricted matter in Queensland’s biosecurity legislation, however there are requirements under the Biosecurity Regulation 2016 in relation to the movement of plant material that may carry pests.

Far North Queensland is a high-risk area for the introduction of plant pests and diseases from nearby Papua New Guinea and Indonesia. The spread of pests into the rest of the state poses a significant risk to our agricultural industries.

Two far northern biosecurity zones have been established in the northern half of Cape York Peninsula to control movement of risk items that may carry pests and diseases southwards to production areas. Plants, plant pests, soils and related equipment must not be moved out of these zones without a biosecurity instrument permit.

Eggs may be laid on the underside or the top side of leaves. The eggs will look a lot like other endemic armyworm/cluster caterpillar egg masses. As with other endemic Spodoptera species, it is likely they may also lay on man-made structures.

Growers and producers should already have strong on-farm biosecurity measures to protect their crops from pests and diseases.

Crops should be monitored for signs of leaf damage leading to defoliation of the crop and report suspected sightings to assist with early detection, and potential treatment.

Good farm hygiene should be implemented for weed control to remove hosts that could build populations.

More information on farm biosecurity is available at farmbiosecurity.com.au or biosecurity.qld.gov.au.

Anyone who comes across fall armyworm is strongly encouraged to photograph and report suspected sightings to the Department of Agriculture and Fisheries on 13 25 23, their agronomist, local biosecurity officer or extension officer.

Images can be sent to the DAF Customer Service Centre; call them on 13 25 23 for advice on how to do this.