Global Plant Protection News

From PestNet

Thursday, 20 February 2020 18:46:47

John Wightman responded to the submission ‘FAW – Devastating pest hits Australian mainland’.

Response for submission

FreshPlaza
https://www.freshplaza.com/article/9191224/devastating-pest-hits-australian-mainland/

Fall army worm detected
A potentially devastating crop pest, the fall army worm, has been detected on the Australian mainland. Just weeks after its first sighting in Australia in islands in the Torres Strait, Queensland Department of Agriculture and Fisheries (DAF) officials confirmed there had been a positive identification of fall army worm at Bamaga on Cape York in far north Queensland.

Biosecurity Queensland general manager of plant biosecurity Mike Ashton said a suspect moth collected at Bamaga was tested and confirmed to be fall army worm. He said it highlighted the pest’s ability to move rapidly in clement conditions. “This detection follows recent confirmed detections on two Torres Strait Islands, Erub and Saibai and underlines how quickly this pest can spread.”

The incursion of the pest, which can be damaging to a range of crops from cereals to fruit trees, means government officials will have to formulate a response swiftly to minimise potential impact. Surveillance programs will now be in full swing in northern Queensland, including rich agricultural regions such as the Atherton Tablelands, along with the coastal fringe from Cairns to Mossman.

“Biosecurity Queensland has proposed a response plan that is being considered by the national Consultative Committee on Emergency Plant Pests,” Mr Ashton said. He said farmers needed to consider their own responses. “Growers should have on-farm biosecurity measures in place to protect their crops from pests and diseases.”

In terms of identification Mr Ashton said fall armyworm larvae were light coloured with a larger darker head. “As they develop, they become browner with white lengthwise stripes and also develop dark spots with spines,” he said. In the moth phase he said adult moths are 32 to 40mm in length wing tip to wing tip, with a brown or grey forewing and a white hind wing.

Source: farmweekly.com.au

Publication date: Wed 19 Feb 2020

Response

Well it is not too much of a surprise – FAW has spread so quickly across Africa and then Asia. This species is polyphagous and includes many crop species. CABI identified an original infestation as the R strain which is linked to rice crops, as opposed to the C = Corn strain. Most of the reports of damage come from corn fields.

We need to remember that it brought high levels of multiple insecticide resistance with it from the Americas (= northern Latin America to Canada) meaning that eradication programs based on insecticide application are likely to be futile. Interventions based on insect pathogens (viruses and bacteria) are going to be much more successful. Interception (light) traps are invaluable for monitoring spread and catching moths before they lay eggs. Relevant experience is available in the research and commercial sector Queensland.

There are several closely related pest species in Australia. This means that natural enemies (ladybirds, parasites and birds) are already here. They will almost certainly have an impact on the survival of fall armyworm larvae – the stage that damages the crop. Natural control agents can change the status of this species from ‘pest’ to ‘just another insect’. This prediction is based on experience with S. litura in India and elsewhere in Asia. The key message is ‘don’t panic’.

Reference

John A Wightman 2018 Can lessons learned 30 years ago contribute to reducing the impact of the fall army worm Spodoptera frugiperda in Africa and India? Outlook on Agriculture 2018, Vol. 47(4) 259–269

An opinon piece written for Grahame Jackson after the FAW conference on FAW in Bangkok April 2019 for digestion in the Pacific. Firstly, will FAW get to the Pacific Countries? 

I have once again visited Google Earth, to review my mental model of what has happened since mid-last year when FAW was identified in S India. The seasonal winds have taken it as far as the South of China, with populations detected in NE India, Bangladesh, Myanmar, and SE Asia. The general trend of air movement during this period was SW to NE, starting with S India’s monsoon winds that mark the start of the rainy season in June.   We now have detected  pioneer populations on the fringe of the massive archipelagos of Indonesia and the Philippines. My prediction is that FAW will proliferate around the SE and E Asian pioneer populations. I do not know about the ‘normal’ wind movements that are encountered through this area, beyond an expectation for them to reverse in the second part of the year. Infilling or back filling from pioneer outbreaks can be anticipated.

The zone that extends across SE Asia from the equator to about 15 deg S is well known for its serious cyclones. If FAW moths are caught up in these huge vortices, survivors that come to earth on land covered with plants that they can eat will presumably initiate well scattered pioneer populations.

The cyclone factor means (to me) that it is highly likely that Pacific Islands will be infested in time. The reports from Africa are a testament to the ability of FAW to travel large distances over land and fill in the gaps rapidly as  a result of the potentially high reproduction rate (one female can lay as many as 2000 eggs). But Africa is a contiguous land mass with the sub-Sahel presenting a vast area of bush with a well dispersed matrix of arable land. Clearly, the Pacific countries are dispersed in a vast area of sea which certainly will not favour FAW. The Pacific countries will not be invaded as rapidly as landlocked nations, but they are by no means immune.

If we consider Western Papua/Papua New Guinea to be the eastern fringe of the Pacific, this huge land mass is likely to be colonized first. Whilst there are areas of extensive arable production (e.g. Markham Valley) much of the agriculture is small scale with farming systems that promote biotic diversity. The implication is that if FAW gets a foot hold in an extensive area of gardens (worst case scenario) the endemic predators and parasites will adapt to FAW and restrict its ability to multiply. However the Papuan populations will remain as a large and in essence, inaccessible reservoir of emigrants that will slowly move into the Solomon Islands and points N, E and S.

Northern Australia is susceptible to invasion from Papua and Indonesia, but is not an area of intensive arable production, although small scale intensive enterprises may be at risk. Clearly preparatory action is advisable https://www.abc.net.au/news/2018-07-31/why-doesnt-the-tropical-north-produce-more-agriculturally/10049286.

What to anticipate? I wish I had access to the field details of the pioneer populations detected in SE and E Asia so that I could understand what a new infestation looks like. It could be that the pioneers are scattered over an area as large as say Guadacanal. If that is the case, small populations may survive undetected for many years living on native vegetation and perhaps on crops in farmers’ gardens. Their numbers will be ‘managed’ by the array of predators and parasites that form part of the fauna of diversified (agro) ecosystems. These are unlikely to be of significance. On the other hand they could be in dense patches that will intensify and, if on intensively farmed land will cause problems.

Answer to your ‘simple’ question

All the above is the background to this answer, together with previous report.

Short answer is ‘not too much if the powers that be act wisely’.

If the pest managers of the Pacific nations promote vigilance by putting in place protocols that:

·       Lead to the early identification of this pest in those areas of their islands that are important for food production (monitoring)

·       Play down its importance on the basis that its feeding activity causes little or no yield loss, and

·       Pass on simple non-pesticidal, mitigative protocols to farmers,  which in any case do not encourage insecticide application,

…natural enemies will adapt to this species and reduce its importance to non-pest status. Note that the closely related S. litura is endemic in the Pacific Region and its parasites, predators, and pathogens will probably adapt to FAW (a data-free-observation based on optimism).

 

In addition, quarantine procedures need to be stepped up. Whilst the moths are prestigious flyers they can also be moved around via the surface transport system that serves most island groups.

 

If the powers that be allow or promote the application of conventional pesticides in the belief that they can manage this pest they will exacerbate the situation:

·       FAW is resistant to most of the commonly applied pesticides

·       They will kill the natural enemies and create human health risks, and allow the potential to proliferate to pest status.

 

Corn is not a staple across the Pacific Region, so that the powers that be might be tempted to shrug off the risk posed by this potential invader, in the mistaken belief that this is FAWs only host. This is not a good idea. A) Sugarcane is also preferred host, and B) its host list includes just about every crop grown by the Region’s farmers.

Conclusion

FAW is a world traveler. It is likely to move towards the Pacific through Indonesia and or the Philippines by normal dispersal flights. However, cyclones may vastly extend this dispersal process. The agricultural practices of the Region do not normally include high insecticide applications this is a trend that may in the long run maintain FAW, when it arrives, at ‘just another leaf eater’ status.