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Fall Armyworm ‘Plague’ Goes Global Threatening Millions of People as Their Staple Food Crops are Devastated

Spodoptera frugiperda, Zimbabwe_sm

The maize pest, Spodoptera frugiperda, is native primarily to Central and South America but, very recently, it has swept across the world at a speed that has spurred comments likening it to a Biblical plague.

It was first recognized in Nigeria in 2016 and, within three years, it had spread into 28 sub-Saharan African countries, including Zimbabwe, a country with 130,000 hectares under maize, and one Castagra is trying to help under its Social Responsibility Program.

Latest reports in May, 2019, say 44 African countries affected and Egypt has just reported a potential fall armyworm infestation for identification which could be a threat to Europe, if confirmed.

Africa has its own armyworm species, Spodoptera exempta, which has experienced a population increase and is usually controllable with conventional pesticides such as Carbaryl, but the new invader appears to have a more damaging appetite destroying up to 40% or more of maize crops, and, what is worse, resistance to many pest control chemicals.

In 2018, fall armyworm (‘FAW’) was discovered in India and this year it is ravaging its way across Asia, including Thailand, Myanmar and China. It is forecast that it will be all over China in 2020.

TIMING AND WEATHER
Time of planting for maize would appear to influence vulnerability to FAW to a remarkable extent.

Shingirayi Nyamutukwa, Chief Research Officer-Acting Head, Plant Protection Research Institute in Harare, Zimbabwe, said “FAW infestations this previous season 2018/19 were generally low, maybe less than 20%, for early planted crops. For late-planted crops, I observed high infestations of up to 100 % in some fields.

“However, the season had poor rains which could have resulted in low reports of pests problems as drying crops became a sign of no hope for farmers in some areas. There are several factors to which I can attribute the low infestations to.

“Some of them include: behavioral change by maize farmers who now scout early for pests in maize fields and institute early control – owing to extensive training of Extension staff and farmers, improved strategy of chemical application targeting maize funnels than full cover spray, improved availability of a variety of control strategies and chemicals, cultural practises like putting sand in funnels during weeding and making sprays of solutions comprising infected larvae in water.”

Nyamtukwa said his surveillance program has a number of natural enemies being identified and training on their conservation is on-going. In some areas, like Chipinge (Manicaland) Mutoko (Mashonaland East) and Mhondoro (Mashonaland West), a lot of farmers are into Push-Pull Strategies involving legumes.

“In such areas, FAW infestations are lower than areas where farmers are not into legume intercrops. Monitoring using traps is in place in all districts of the country but moth numbers, not a true reflection of what is taking place in the fields,” he concluded.
Fall armyworm, on maize, Zimbabwe_sm

BAD OLD DAYS…STILL
When we think of insect pests, pesticide sprays and powders come immediately to mind as being a way of dealing with them. Those of us old enough to recall the use of DDT, a white powder insecticide, know what a price you can end up paying with damage to the environment and ill effects on humans.

DDT was first developed in the 1940s and used widely to combat malaria. It is classified as a probable human carcinogen by U.S. and international authorities.

“I remember using DDT to kill what was erroneously considered nuisance insects such as wasps. Then, it was banned in the UK after they discovered that it was threatening the very existence of ospreys by causing their eggshells to get so thin that they would break and the clutch fail,” commented Castagra’s VP of Social Responsibility, Nigel Horsley.

“This threat to these water hawks was the first time I experienced a bio-indicator pointing to environmental danger. Unfortunately, it is still being manufactured in countries like India, North Korea and China and also being used in South America and parts of Africa.”

HOW DISEASES SPREAD
“It is utterly baffling and frankly amazing how quickly FAW has spread across the world. It’s the very stuff to feed conspiracy theories, but there will almost certainly be a simple and natural explanation that we are currently unaware of,” continued Horsley.

“For instance, my observations while staying in the UK, I noted how the European hornet, Vespa crabro, has a predilection for nibbling on young ash tree growth with the stems dying off a few months later from Chalara ash dieback fungus Hymenoscyphus fraxineus.

“I believe the deadly spores are carried in the mandibles of the hornet and are transferred to healthy ash, which would help explain the rapid spread.

Ash dieback disease has swept through Europe killed hundreds of millions of ash trees in the past 20 years. It is believed it entered the UK in a consignment of horticultural goods in 2012. Infections in the estimated total of 125 million ash trees have been confirmed across 80% of Wales, 68% of England, 32% of Northern Ireland and 20% of Scotland.

“If the hornet turns out to be a vector, then it could help explain the rapidity of that fungal disease’s spread,” stated Horsley.

LONG DISTANCE FLYERS
“In the case of FAW, the moth can fly 100 kilometers a night and double or triple that with a high tailwind, but why suddenly now and how has it managed these vast distances, including oceans? There does appear to be climatic instability being experienced in Africa, whether it’s climate change or temporary instability, that remains to be seen. However, what it can result in are large, dynamic movements of air masses which can transport insects vast distances.

'Y' Moth_sm

“We know day‐migrating butterflies at lower altitudes followed by a speedboat during a sea‐crossing in Central America, have been shown to be able to correct for drift caused by side winds (Srygley 2003). But, if you are a noctuid moth like FAW, and your hard-wired evolutionary survival strategy is to simply spread, then you can opt for higher altitudes for distance. We know some flying insects can detect atmospheric conditions and can pick optimum flying conditions.”

Chapman et al. (2015a) reported that the noctuid ‘Y’ moth predominantly depart on migration flights in downwind conditions (to the south in autumn and to the north in spring) and quite unexpectedly in winds of stronger speeds compared to songbirds. The wind speeds utilized by the moth in spring was the fastest of all, resulting in relatively high ground speeds.

Monarch butterflies perform a super long migratory route. Five to six generations of Painted Lady butterflies are involved in covering the annual round‐trip distance of approximately 15,000 km from West Africa to northern Scandinavia and back (Stefanescu et al. 2012). A Green Darner dragonfly, Anax junius, travelled over 5,000 kilometers after heavy weather and tiny spiders are regularly found hundreds and even a thousand miles off-shore after being transported by the wind.

In 1960, a large migration of Diamondback moths was carried by winds and tracked over 2,000 km from the Baltics. The diamondback moth is said to be the world’s worst insect pest of brassica vegetable crops such as cabbage, canola, broccoli, cauliflower, and kale – costing farmers US$4-5 billion annually worldwide.

OVERWHELMING FAW INVASION
The sheer strength of the FAW invasion in Africa has been overwhelming. With so many smallholder farmers with severely limited funds for conventional pesticides, many have taken to using local remedies of herbal hand-applied liquid concoctions and encouraging the proliferation of local ant predators.

What is generally agreed, is no-one wants the nuclear option of relying on conventional pesticides with toxic chemicals that can damage the immediate environment and harm humans if not properly protected. Governments and farmers want Integrated Pest Management but cheaply.

Strategies can include genetically modified maize plants, bacteria, viruses, fungal spores, nematodes, to parasitoid wasps, and, of course, natural pesticides.

“Insects destroying pest insects. I like that and have seen it in action many times,” said Horsley.

LITTLE WASP HOPE
“In Brazil, field trials with the tiny wasp, Telenomus remus, have shown to be highly effective against FAW. T. remus arrived in Africa prior to FAW, so, it would appear to be a major potential pest control option as these tiny wasps can be reproduced commercially in their millions as is happening with another excellent parasitoid wasp Trichogramma presiotum and Chelonus insularis. You can buy T. presiotum from a company in Arizona.

Wasp eating Cabbage White caterpillar, UK_sm

“Many control options are available but it is gearing up to use them, understanding what to use, when, the training process, funding, are all critical factors in this truly overwhelming global plague which will take time while millions of people will continue to suffer from corn shortages. I just hope this situation gets quickly recognized as a global responsibility and is tackled as such.

“At the end of the day, you may and probably will be able to control FAW with a suite of control measures, but you still won’t be able to control the weather which can wipe out crops even more effectively than pest plagues and that deadly combination would appear, whether temporarily or permanently, to be a trend in places like Zimbabwe,” concluded Horsley.