This page last updated: 11/05/2013
*** CURRENT SITUATION: LOW-MEDIUM ARMYWORM ACTIVITY IN ETHIOPIA and KENYA ***View BBC NEWS Africa report on Zambian armyworm situation here (Dec 24th 2012).
View BBSRC/Global Food Security video diary of armyworm outbreaks in Zambia - YouTube here (Apr 29th 2013).
ANY QUESTIONS? If you have any questions about African armyworms or their biological control, please email:
Ken Wilson (Lancaster University, UK): email@example.com
Current situation: In Ethiopia, the first African armyworm (AAW) outbreaks of the season were reported in Fedis and Babile Woredas (Districts) in eastern Ethiopia. On April 25th, AAW farmers’ forecasters who were trained and equipped through the OFDA-sponsored community-based armyworm monitoring, forecasting and early warning (CBAMFEW) project issued an alert on a
possible AAW outbreak in Fedis, Babilay and the surrounding Woredas (districts) and adjacent areas. The occurrence of the outbreaks reinforced the relevance of the CBAMFEW program and earned the forecasters trust among the farming communities and other partners. Ground control operations were organized by the MoA’s regional agricultural office, but details were not available at the time this prepared was compiled (DLCO-EA).
AAW outbreaks were reported in Moshi rural, Rombo District in Kilimanjaro Region as well as in Meru District in Arusha Region in northern Tanzania during the third week of April. The outbreaks were controlled by the affected famers with material and technical support from the MoA. AAW activities were not reported in other countries during this period (DLCO-EA, IRLCO-CSA, PHS/Tanzania).
Forecast: AAW outbreaks are expected to continue in Ethiopia and Kenya and may begin appearing in eastern Uganda. Active monitoring and reporting will remain essential. AAW outbreaks will fade away in most of Tanzania including the northern part and the central and southern outbreak countries will remain free of AAW during the forecast period (AELGA, DLCOEA, IRLCO-CSA).
With thanks to Dr Yene Belayneh at USAID. You can learn more about ETOP activities and projects by visiting: http://transition.usaid.gov/our_work/humanitarian_assistance/disaster_assistance/locust/
Armyworms on mature maize plants in Tanzania (left - photo: Gasana Damian Rwabufigiri) and Lesotho (middle - photo: FAO LESOTHO), and mature maize plants destroyed by late-stage armwyroms (right - photo: FAO LESOTHO).
Devasting armyworm outbreaks in Zambia, Malawi, Tanzania, Zimbabwe, Botswana, Namibia, South Africa, Lesotho and now Ethiopia: There are numerous press reports about these extensive armyworm outbreaks (click on the highlighted links to read the stories):- The New Age (April 5th): "Army Worm Outbreak Worries Farmers" - SOUTH AFRICA: Emerging farmers in the OR Tambo area are concerned at the recent "unusual" outbreak of army worms which started to make their way onto their maize plantations about a week ago.
- allAfrica.com (April 4th): "South Africa: Swift Actions Taken to Rectify the Army Worm Outbreak" - SOUTH AFRICA: The Honourable MEC for Rural Development and Agrarian Reform (DRDAR) Zoleka Capa has called for calm among farmers that are affected by the recent outbreak of army worms that are destroying maize in parts of the OR Tambo District Municipality
- Mwebantu.com (April 1st): "Hunger Looms in Nangwenya Ward in Chongwe District" - ZAMBIA: Acute hunger has hit villagers in Nangwenya Ward in Chongwe distrct in Lusaka province .... Ms Sakala [Ward Councillor] attributed the hunger situation in the area as due to [army] worms that ravaged the farms as well as the dry spell that Nangwenya Ward experienced in the 2012/2013 farming season"
- SADC Food Security Early Warning System (April 1st): "Agromet Update Issue 04" - SOUTHERN AFRICA: Armyworm outbreaks that were reported earlier in the season in several countries in the region have largely been contained. These countries include Botswana, Malawi, Tanzania, Zambia and Zimbabwe. However, recent reports indicate outbreaks occurring in South Africa and Lesotho. Efforts are currently underway to contain the outbreak in Lesotho.
- Reliefweb (UN) (March 30th): "FEWS NET: LESOTHO Remote Monitoring Update - March 2013" - LESOTHO: Severe armyworm infestations likely to impact 2012/2013 production.
- FAO LESOTHO (March 28th): "Armyworm Outbreak in Lesotho - March 2013" - LESOTHO: Since late January 2013 an African armwyorm outbreak has been reported in Lesotho. So far 8 districts of a total of 10 have reported infestation of African Armyworm, a deleterious pest of crops and rangeland herbage.
- Farmbizafrica.com (March 27th): "Army worm sex trap help farmers fight voracious moth" - KENYA: subscription required
- IRIN news (March 25th): "Mixed picture for Lesotho's food security" - LESOTHO: It's a chilly autumn morning and Ntja Mphale, 62, and his wife, Malehlohonolo, are hoeing a dew-covered field just outside their village of Machache, 43 km from Lesotho's capital, Maseru.
- Farmer's Weekly (March 17th): "African Army Worm Outbreak May Be Over" - SOUTH AFRICA: Dr Gerhard Verdoorn, head of the Griffon Poison Information Centre, said that the recent outbreak of African army worm was the worst experienced in 20 years.
- Lesotho Times (Feb 27th): "Armyworm Wreaks Havoc" - LESOTHO: Agriculture Minister Litšoane Litšoane last week said the invasion by armyworms in the past month has the potential to further render Lesotho severely food insecure.
- Lesotho Times (Feb 21st): "Army Worm Threatens Good Harvest" - LESOTHO: An army worm outbreak threatens to dash Basotho farmers’ hopes of a good maize harvest this year.
- The New Age (Feb 7th): "Armyworms Marching" - SOUTH AFRICA: Farmers in the Ngaka Modiri Molema and Dr Ruth Segomotsi Momphati districts have been warned to be on the lookout for a possible outbreak of African armyworms after indications that infestations of the worm had been seen in the region.
- News 24 (Feb 5th): "Farmers Warned of Armyworm Outbreak" - SOUTH AFRICA: Farmers were warned to be on the lookout for infestations of African armyworm after an outbreak of the pest in the North West, an official said on Tuesday. see also SA Government Information Service
- allAfrica.com (Jan 31st): "Zimbabwe: Armyworm Outbreak Destros Crops'" - ZIMBABWE: Masvingo Bureau — An armyworm outbreak and flooding have destroyed over 10 000 hectares of crops in Masvingo. The armyworm has destroyed vast tracts of grazing pastures across the province especially in the Masvingo and Zaka districts.
- Manica Post (Jan 26th): "Zimbabwe: Armyworms wreak havoc'" - ZIMBABWE: The staple maize crop and green pastures in Manicaland have come under severe attack from armyworms.
- The Southern Times (Jan 25th): "Armyworms threaten food security in SADC'" - SOUTHERN AFRICA: A plague of armyworms is threatening food security in southern Africa following invasion of crop fields in countries like Botswana, Namibia, Zambia and Zimbabwe.
- Allgemeine Zeitung (Jan 25th): "GroBe Schaden durch Kommandoraupe'" - NAMIBIA: Zahlreiche Regionen betroffen - Wenig Regen tragt zur Misere bei.
- Reliefweb (UN) (Jan 25th): "Current Situation & Update: Armyworm Outbreak in Southern Africa" -SOUTHERN AFRICA: Several countries in the Southern Africa region have suffered outbreaks of the African armyworm, a deleterious pest of crops and rangeland herbage.
- NewsDay (Jan 23rd): "EU avails $ 75 000 for Armyworm Fight" - ZIMBABWE: The European Union (EU) has released $75 000 towards curbing the spread of the armyworm which has destroyed cereal crops in most parts of the country.
- allAfrica.com (Jan 21st): "Zimbabwe: 'Prepare for Another Army Worm Attack'" - ZIMBABWE: Farmers should prepare for another army worm outbreak in February, as some of the worms that recently hit the country are suspected to have pupated in pastures and gone into the ground to lay eggs to raise another generation, the Department of Research and Specialist Services has warned.
- allAfrica.com (Jan 16th): "Namibia: North Battles Invasion By Army Worms" - NAMIBIA: Several villages in the Omusati, Oshana and Oshikoto regions face a devasting threat from an outbreak of ravenous army worms.
- NBC (Jan 15th): "Army Worms Spread to Omusati" - NAMIBIA: The outbreak of armyworms that was first reported in the Omusati region has now spread to the Oshana region.
- NewsDay (Jan 15th): "Heavy Rains Dampen Spirits" - ZIMBABWE: After years of consecutive droughts, Tsholotsho farmers in Matabeleland North province were hoping for a better farming season, but torrential rains and an armyworm outbreak have dampened their hopes of a successful faming season.
- Mmegionline (Jan 15th): "African Armyworm Spreads Across Country" - BOTSWANA: According to the Ministry of Agriculture, the African armyworm has now covered most of the country, except for Kgalagadi District.
- IRIN news (Jan 14th): "Zimbabwe: Army Worm Outbreak Threatens Zimbabwe's Food Security" - ZIMBABWE: An army worm outbreak threatens to worsen food security in Zimbabwe, where close to 1.6 million people already face food shortages ahead of the March harvest.
- University of Greenwich (Jan 11th): "New Biological Control will Combat Armyworm Causing Food Crisis in Africa" - UK: A large number of extensive outbreaks of African armyworm ravaged Zambia throughout December 2012, affecting 59 000 farmers and causing a national emergency. Hundreds of resource-poor farmers lost their entire crops.
- The Herald via allAfrica (Jan 11th): "Zimbabwe: Rains Set to Intensify Armyworm Outbreak" - ZIMBABWE: Moist winds coming into Zimbabwe from the north may bring more moths that will develop into armyworm and trigger fresh outbreaks of the pest, the Department of Research and Specialist Services has warned.
- The Zimbabwean (Jan 10th): "Armyworm Hits Matland" - ZIMBABWE: The leaf–ravaging worms were first discovered in Richmond on New Year’s day and have since spread to most plots in the area. Farmers who spoke to The Zimbabwean said the situation was serious.
- Mmegionline (Jan 10th): "African Armyworm Outbreak Reaches Botswana" - BOTSWANA: The Ministry of Agriculture has announced the outbreak of an African Armyworm, notorious for destroying a range of grass and crops. The worm has been found in Mmopane, Gakgatla, Gweta, Makalamabedi, Shorobe, Shashe, Maun, Matlapana, Chanoga and Gumare.
- BusinessDay live (Jan 9th): "Army Worm 'May Threaten Food Security' in Zambia, Zimbabwe" -ZAMBIA/ZIMBABWE: Authorities in Zimbabwe and Zambia must closely monitor the recent army worm outbreak in the two countries to determine the impact it may have on food security, the United Nations World Food Programme (WFP) says.
- Reliefweb (UN) (Jan 9th): "Ministry Reports African Armyworm Outbreak" -BOTSWANA: The Ministry of Agriculture has informed the public that there is an outbreak of the African army worm which destroys both crops and range grasses.
- AfriqueJet.com (Jan 9th): "African Army Worm Detected in Botswana" - BOTSWANA: An outbreak of African army worm, which destroys crops, has been announced in Botswana. The country’s Ministry of Agriculture Tuesday announced the outbreak of the pests in some parts of the country south of the capital and the North-West District.
- Zimbabwe Post (Jan 8th): "Maize Crops Hit by Armyworms" - ZIMBABWE: re-run of post below.
- BloombergBusinessweek (Jan 7th): "Zimbabwe's Corn production Threatened by Armyworm Infestations" - ZIMBABWE: Half of Zimbabwe’s 10 provinces are infested with armyworms that are threatening corn production because the country has a limited supply of the pesticide required to eradicate them.
- Zambia Daily Mail (Jan 8th): "State Intensifies Spraying Against Army Worms in L/stone" - ZAMBIA: Minister of Agriculture and Livestock Emmanuel Chenda says officers from his ministry have intensified spraying of chemicals in Livingstone where army worms have been detected.
- Zambia Daily Mail (Jan 8th 2012): "Zambia Emerges from Threat of Army Worms" - ZAMBIA: Zambia has just emerged from a ‘war’ which threatened her national and household food security; the enemies that almost crippled Zambia’s food security were the army worms.
- Zimbabwe Broadcasting Corporation (Jan 5th): "Armyworm Outbreak Hits Nation" - ZIMBABWE: An armyworm outbreak has hit some parts of the country affecting hundreds of hectares of maize and pastures in Mashonaland West, Mashonaland Central, Matabeleland North, Manicaland and Midlands provinces.
- Sunday Mail (Dec 30th): "Severe armyworm outbreak looms" - ZIMBABWE: Zimbabwe should brace for an extensive armyworm outbreak this farming season following the significant rainfall the country has received, an official has said.
- The Maravi Post / Malawi News Agency (Dec 28th): "Army Worms Warning Issued to Malawi Farmers in Mchinji" - MALAWI: Mchinji - Farmers in Malawi's central district of Mchinji have been warned of a looming armyworm outbreak which has affected neighbouring Zambia.
Armyworm in Kwesha, Masaiti District, Zambia - December 2012: photos (c) Emmanuel Mutamba
Armyworm summit in Zambia, 23rd December 2012: left to right - Patrick Kangwa, Prof Ken Wilson, Dr Guy Scott (Vice-President), Dr Mukanga Mweshi, Mr Mtwawa, Borther Paul, Donald Zulu. photo (c) Ken Wilson
- Zambia Daily Mail (Dec 21st): "Army worms: It's time to replant" - ZAMBIA: The government's swift action on the crop-eating army worms is highly commendable and clearly demonstrates its intent to make agriculture the mainstay of the economy.
- Zambia Daily Mail (Dec 20th): "Replant with certified seed, Scott urges army worm affected farmers" - ZAMBIA: Vice-President Guy Scott has urged farmers whose fields were invaded by army worms to ensure that they replant certified seed.
- DailyNews (Dec 19th): "Armyworms destroy 280ha of maize farms in Sumbawanga" - TANZANIA: An armyworm outbreak in Muze Ward, Sumbawanga District, has resulted in the destruction of more than 280 hectares of maize crop. The armyworms are reported to have, for the past two weeks, adversely destroyed farms along the Lake Rukwa Basin, something that is inflicting fear in farmers in the surrounding areas that more fields will be attacked.
- ShanghaiDaily.com (Dec 12th): "Zambia describes army worm invasion a disaster" - ZAMBIA: The Zambian government has described the outbreak of army worms which have destroyed large swathes of planted crops in some parts of the southern African nation as a disaster.
- Lusaka Times (Dec 12th): "Army worms threaten food security " - ZAMBIA: Former Agriculture Minister Eustarkio Kazonga says army worms which have invaded fields in some parts of the country pose a threat to food security in the country.
- Times of Zambia (Dec 12th): "Army worm invasion: Govt, farmers spray ravaged fields" - ZAMBIA: The Government is working with farmers to spray fields affected by army worms and will continue with the exercise in the next 10 days in various parts of the country.
- Zambia Daily Mail (Dec 12th): "ZNFU worried about army worms" - ZAMBIA: The Zambia National Farmers’ Union (ZNFU) has expressed worry at the rate at which army worms are spreading and fears that the infestation will cause a huge economic lose if it is not curbed quickly.
- Zambia Reports (Dec 12th): "Now Army Worms Spread to Five Provinces Prising Fears of Poor Maize Harvest" - ZAMBIA: Army worms which are wrecking havoc on agricultural fields have now affected five of the ten provinces in the country, Zambian Vice President Guy Scott told parliament on Wednesday.
- NZweek (Dec 12th): "Zambia describes army worm invasion a disaster" - ZAMBIA: The Zambian government has described the outbreak of army worms which have destroyed large swathes of planted crops in some parts of the southern African nation as a disaster.
- Zambia Daily Mail (Dec 12th 2012): "Army worm invasion in Kabwe worsening" - ZAMBIA: Kabwe district commissioner Patrick Chishala says 70 percent of maize fields in Kabwe have been invaded by army worms.
susceptibility to viral disease rather than protects (see Publications).
Click on the logos below to see press stories related to this paper:
photo (c) Wilfred Mushobozi
photos (c) Wilfred Mushobozi
photos (c) Ken Wilson
The Zimbabwean (12th Jan 2011): "Armyworm destroys maize" - outbreaks reported in Bulawayo, Zimbabwe
ZBC (11th Jan 2011): "Armyworm outbreak reported countrywide" - outbreaks in greater Harare and Bulawayo, Zimbabwe
Panapress (10th Jan 2011): "Armyworm devastates crops in Zimbabwe" - outbreaks in northern Zimbabwe
The Citizen (6th Jan 2011): "DC sounds alert as rats, worms overrun villages" - outbreaks in Morogoro and Mtwara, Tanzania
Afrique Avenir (4th Jan 2011): "Armyworm outbreak devastes Zimbabwean province" - outbreaks in Zimbabwe
photo (c) Wilfred Mushobozi
IRINnews (20th Jan 2010): "Kenya: worm outbreaks threaten food security" - outbreaks in central & eastern Kenya
Reuters Africa (18th Jan 2010): "Dry spell, army worms damage Malawi crops" - outbreaks in Malawi
Daily Nation (10th Jan 2010): "The army worm must be stopped " - outbreaks in Ukambani, Kenya
The Citizen (31st Dec 2009): "Armyworm scourge spreads to ten regions" - outbreak risk in Tanzania
The Citizen (30th Dec 2009): "Red alert as armyworms invade two districts" - outbreaks in Tanzania
Nature News (24th Dec 2009): "Whatever happened to ... Liberia's caterpillar plague" - click here for January 2009
Map showing the distribution of African armyworm outbreaks in Africa
(data from Figure 3 in Rose et al. 2000, and Haggis 1984).
Like the infamous desert locust, the African armyworm has such a major impact because the adult stage (a moth) is highly migratory and the location, timing and magnitude of its outbreaks are difficult to predict.
During the long dry season (c. May to September), armyworms occur at very low densities in coastal regions, and other areas where green vegetation is available all year round.
The first outbreaks of the season occur when moths from these low-density populations are concentrated by the convective winds associated with the first rainstorm of the short rains in October-December. These first outbreaks generally occur in identified primary (10) outbreak areas in Tanzania and Kenya. They then spread sequentially across the continent at roughly monthly intervals over a period of 5-8 months, as successive generations of adult moths migrate on the prevailing winds and initiate new high-density larval outbreak cycles (Figure 1).
The number of outbreaks varies considerably between countries and from year to year, but there are some clear patterns. For example, when the number of outbreaks in Tanzania is high, they also tend to be high in neighbouring Kenya (Figure 2), which is due in part to moths migrating between the two countries.
The most reliable predictor of the annual magnitude of armyworm outbreaks in East Africa is the amount of early-season rainfall: when the rains in November-December are heavy and frequent, relatively few armyworm outbreaks occur throughout the region, whereas when the early-season rains are poor, outbreaks are much more common and widespread (Harvey & Mallya 1995). The exact cause of this relationship has yet to be established.
African armyworms play host to a highly specific baculovirus: Spodoptera exempta nucleopolyhedrovirus (SpexNPV).
Larvae become infected when they ingest vegetation contaminated with virus occlusion bodies (OBs). The OBs break down in the alkaline conditions of the insect’s mid-gut and the virus replicates within host cells, generating millions of new OBs. Within 3-5 days the larvae die and they exhibit a characteristic inverted-V shape as they hang from vegetation (see photo). Soon, their cuticle (skin) ruptures, liberating the OBs on the vegetation where they can infect conspecifics.
Although extensive epidemics of SpexNPV often cause armyworm populations to crash (causing up to 98% mortality; Rose et al. 2000), these natural disease outbreaks are usually far too late in the armyworm seasonal cycle to prevent major crop damage (see below). Ongoing research on the biology, ecology and genetics of SpexNPV is trying to assess its potential use as a microbial pesticide.
SpexNPV-infected armyworm larvae on pasture. photo (c) Bill Page
Summary of previous research
Previous research has shown the following:
Application of chemical pesticide against armyworms on pasture. photo (c) Ken Wilson
Most viruses are transmitted in a density-dependent fashion and so rely on interactions between hosts for transmission and persistence. This becomes a problem in low-density populations due to a shortage of new hosts to infect. Consequently, viruses have evolved a number of mechanisms to ensure persistence in the face of low or variable host densities. For the insect viruses, these include long-term survival in the environment, alternative hosts and vertical transmission.
While it has long been thought that horizontal transmission and persistence in the environment (outside of the host) are the main means of baculovirus survival, it is becoming increasingly evident that many species harbour ‘covert’ infections that are passed from adults to their offspring. Our understanding of this process, even in a group as widely employed as insecticides as the baculoviruses, is poor and we have little idea of how covert infections contribute to the maintenance of virus populations in the field.
There are two types of covert virus infection; ‘persistent’ infections and ‘latent’ infections. They are distinguished by the degree to which virus-encoded gene products are expressed and whether or not infectious virus particles are present.
Persistent virus infections are characterised by a constant low-level production of virus particles within an infected cell. These infections represent a balance between the host and the virus, which may be maintained through the interaction of the cells and the virus alone, interaction with the host immune system, the production of defective interfering virus, or a combination of all three. Persistent virus infections still express the full range of viral genes, although this expression may be down-regulated.
In a latent virus infection, the viral genome, and possibly some virus-encoded products, are present, but infectious virus particles are not formed. Latent virus infections involve a shut-down in viral gene transcription with only those genes involved in maintaining the latent state being expressed. Latent infections do not represent a dead-end for the virus as, with an appropriate triggering stimulus, the infection can revert to a fully reproductive overt infection.
For the majority of these ‘covert’ infections in insects, it has yet to be determined whether they represent persistent or latent infections, but clearly their prevalence indicates that they may play an important role in the survival and persistence of the virus in host populations.
Indeed, if our understanding of the S. exempta-SpexNPV interaction is correct, it is the vertically-transmitted virus, and not virus in environmental reservoirs, that is important in initiating epizootics.
Armyworm Baculovirus Project
The African Armyworm Baculovirus Project is a consortial project with partners in the UK and Tanzania. The main partner organisations are Lancaster University, UK; University of Greenwich, UK; EcoAgriConsult Ltd, Tanzania; and the Tanzanian Government's Ministry of Agriculture and Food Security.
The ultimate goal of the African Armyworm Baculovirus Project is to further our understanding of the natural interaction between an insect host, the African armyworm (Spodoptera exempta), and its virus (SpexNPV), with a view to determining the impact of the virus on its host’s outbreak dynamics and how this might ultimately be manipulated in a novel, Africa-wide strategic control system (Box 2).
The funding for this research comes from a range of sources including The UK's Department for International Development (DfID), the Biotechnology and Biological Sciences Research Council (BBSRC), the Natural Environment Research Council (NERC) and the United States Agency for International Development (USAID). Current research is funded by the BBSRC-DFID's Sustainable Agriculture Research for International Development (SARID) programme and DFID's Research Into Use programme.
The SARID project is examining the spatio-temporal pattern of armyworm outbreaks, as well as variation in natural levels of SpexNPV in the wild (prevalence appears to vary from zero to nearly 90%) and molecular genetic variation in the vuirus. The RIU project is funding the building of a baculovirus processing plant (see below), which will take the crude SpexNPV-infected caterpillars and turn it into a dry powder formulation with a shelf-life of years. This project is also providing farmers in areas at high risk from armyworm attack with pheromone traps to monitor local moth activity (see photo below - the pheromone trap is hanging from the tree). The trap attracts moths that have migrated into the area and warns the farmers that armyworm infestations are likely in the coming few days. With this information they have time to acquire pesticide to control the armyworm and protect their crops. This 'community-based forecasting' approach has proved to be very successful. The RIU project in Tanzania plans to extend this network of local forecasters and ultimately to provide these communities with SpexNPV so that they can control the pest with a cheap and environmentally-friendly biopesticide.
For enquiries about the African Armyworm Baculovirus Project, email Professor Ken Wilson (firstname.lastname@example.org) or one of the other project partners.
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Armyworm caterpillars (large late-instar larvae):
Armyworm infected with SpexNPV baculovirus: