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Project Record

Objectives:

To reduce poverty by increasing cereal production through adoption of effective and appropriate IPM technologies for the control of armyworm outbreaks by resource poor farmers in East Africa.

Background:

Tanzania is one of the poorest countries in Africa, where rural poverty is pervasive and in which agriculture plays a dominant role in the economy. The African armyworm is a migratory pest of cereals, pasture and rangeland, is widely distributed in Africa south of the Sahara, and demonstrates great variability in the extent and severity of infestation. The areas from which infestations have been reported, and the frequency of attack, have increased since 1970. Tanzania has long suffered from the widespread depredations of armyworm outbreaks that appear to be increasing more regularly and more seriously as agricultural production continues to expand. Outbreaks normally occur during the early part of the main rainy season December-March, just after Maize, the main food crop, has been planted. Yield losses within an outbreak area are up to 50%, although 30% loss in recently planted maize has been estimated as an average loss. Currently, poor farmers have two strategies to deal with armyworm outbreaks. The first is to use chemical insecticides at a cost of at least 6,000 Tanzanian shillings (US$10) per ha, but these are beyond the financial means of most poor farmers. The MoA supplies some insecticide to the poorest farmers in each district, but currently, due to the need to import pesticide, and with hard currency restrictions, it is only able to supply between 10%-30% of their needs during outbreak years. Increasingly, farmers are encouraged to buy their own insecticides, with government support being provided only during emergencies. The poorest families are the group most vulnerable to armyworm, as they have least resources with which to cope through buying pesticides to prevent damage, or through having the resources to afford replanting after an attack. The resource poor farmers, again a high proportion of them women tending small plots, depend for armyworm control on insecticide supplied by the Tanzanian crop protection service, either free or at reduced cost. However, while the government tries to supply these poorer households, financial constraints to buying imported pesticide has meant that in the last outbreak only 10%-30% of those qualifying for insecticides actually got them, in most districts. The need to import chemical pesticide also makes it difficult to get it to the farmers in time to control outbreaks. This is a particular problem in Tanzania, where armyworm outbreaks start. In 1999, staff on the preceding project were able to warn the Kenyan authorities of the likelihood of an armyworm outbreak spreading from Tanzania, in time for them to procure chemicals. Developing local sources of effective armyworm control agent (NPV or neem) would significantly increase the availability of control agents, during the early phase of armyworm outbreaks. Armyworm can also have a damaging effect on livestock production, because armyworm feeding continuously on grasses such as Cynodon spp stimulates the production of high levels of cyanide (cyanogenesis), making such pastures unfit for cattle. Normally, cattle feed through light peripatetic grazing that does not stimulate cyanogenesis in pasture grasses. The indications are that this phenomenon is, again, mainly a feature of drought years, when pasture is already under stress, and the effects on already weakened livestock may be severe. The high cost and limited availability of insecticide has also prevented the implementation of strategic control of primary outbreaks. These often occur in small areas on low value rangeland, and are the focus for armyworm outbreaks that later spread to larger areas of cereal crops. This project, by developing new alternative biopesticide technologies, seeks to reduce dependence on environmentally damaging chemical insecticides and replace them with environmentally acceptable and locally produced alternatives.

Intended Outputs:

Project workplan validated.

Determination of efficacy of candidate neem and NPV formulations under laboratory conditions.

A review of the potential of neem against armyworm in Tanzania.

Report evaluating the efficacy of neem and NPV under field conditions.

Ecology of SeNPV in relation to armyworm population dynamics and the potential for strategic control determined.

A strategy for the local production of neem and NPV completed.

A socio-economic assessment of the viability of producing and using SeNPV and neem.

Dissemination of results through papers, publications and mass media.

A strategy to promote and implement novel controls developed and implemented.

The capacity of local counterparts enhanced.

Progress and Impact:

The initial workshop enabled assumptions to be validated and project activities planned in discussion with stakeholders. This generated a better understanding of the population who are at risk from armyworm outbreaks and of the adoptability of the proposed technologies.

Laboratory evaluations confirmed that both NPV and neem were active against armyworm at levels that could viably be used in the field. Initial field trials suggested SpexNPV could be effective at application rates between 5x1011 and 5x1012 occlusion bodies (OB) per ha.

Review of the neem literature indicated the potency of neem against armyworm, and discussions at the workshop confirmed that neem was available in armyworm outbreak areas, and could therefore be harvested and used where resources were not available to purchase pesticides.

Field trials conducted in 2001, 2002 and 2004 showed that SpexNPV can be used successfully to control armyworm outbreaks, and is therefore a viable substitute for chemical pesticides. These trials also showed that SpexNPV at rates as low as 1 x1012 OB per ha when applied using ground. based or aerial application can be as effective as chemical insecticides in controlling armyworm. The same trials have shown that extracts of neem leaves and seeds can be used to kill armyworm. While these are not as effective as either chemical insecticides or the NPV, use of neem would be useful to local communities who lack access to other resources.

Ecological studies have shown that SpexNPV is surprisingly widespread in Tanzania in adult armyworm moths. It is however found as a non symptomatic, or latent, infection, the first scientific confirmation of a latent NPV in an African insect. The role of the covert infections in relation to natural outbreaks of overt lethal NPV disease in the larvae is as yet unclear. Attempts to use known initiators of latent NPV to produce active SpexNPV infections have so far failed. It is felt though that SpexNPV disease is an important factor influencing the population dynamics of armyworm and understanding this relationship could be a key to better forecasting of the severity of outbreaks. The virus is present as a wide variety of genotypes and 60 genotypes have already been identified and collected by CEH Oxford. A number of these genotypes have been cloned and assayed but none has proved individually to be more pathogenic than the wild type mixture used in these field trials.

The project has shown that low technology field production of SpexNPV is viable in Tanzania and that the virus could replace some imported pesticides. The head of Pest Control Services Tanzania visited EMBRAPA in Brazil to be trained in low cost NPV production techniques that they had developed there, based on harvesting infected field populations. He judged these to be appropriate for use in Tanzania and that the techniques could produce armyworm NPV at a cost comparable to that in Brazil (1.50US$ per hectare). This is much lower than the cost of current imported synthetic insecticides (around 10US$ per hectare). Thus, adapting techniques developed by the collaborating institute (EMBRAPA) that are already used on 2 million hectares in Brazil, offers a cheap way to produce stable formulations of SpexNPV.

The project has confirmed that it is a viable strategy in Tanzania to produce SpexNPV for armyworm control by spraying naturally-occurring armyworm outbreaks with an inoculating dose of SpexNPV then harvesting the diseased larvae. With future work it is hoped to adapt the clay-based formulation techniques developed by EMBRAPA in Brazil, for use in Tanzania. The system for harvesting infected field populations also still needs some additional R & D work as the Brazilian larval collection system is not appropriate for African armyworm. The development of low cost NPV is crucial, as the cost of chemical insecticides is the major reason why 65% of poor farmers cannot control armyworm.

Project Conclusions:

Viable alternative control technologies for armyworm that are appropriate for Tanzania have been developed, evaluated and adopted. The use of SpexNPV, has been adopted as National Policy by Tanzania. The use of local neem is already being promoted in target districts by PCS. Fieldwork has confirmed that the candidate technologies work well in practice, and have been used successfully both in small plot trials and for large scale aerial application. Work has started on adapting the Brazilian model for field production of NPV so that the product is cheap enough for poorer farmers in Tanzania.

General Notes:

See also the TECA Record Biological control of armyworm (Spodoptera exempta) in Tanzania

Publications:

Mugo W. 2001. Armyworms invade Kenya, P 18. Short article in The Daily Nation, 1 February 2001



RANDERSON, J. (2003) Corpses of Dead Kill Living. New Scientist p12, 13 December 2003 (A)



DIXON, D. (2004) Biological weapons used against armyworm. Appropriate Technology, 31 (1) 60-61.



GRZYWACZ, D. and MUSHOBOZI, W. (2004) A local solution to African Armyworm. Biocontrol News and Information, 1: 7-8N.



GRZYWACZ, D., PARNELL, M., MUSHOBOZI, W. and WILSON, K. (2004) Development of Spodoptera exempta nucleopolyhedrovirus (SpexNPV) for the control of African armyworm in East Africa. Oral presentation at Annual Meeting Society of Invertebrate Pathology, Helsinki, Finland, 31 August-6 September 2004.

Paper File Reference:

ZA0460

Associated References:

R6746