Armyworm forecasting and control
About

Swarms of armyworms, the caterpillars of a migratory moth (Spodoptera exempta), can have a devastating impact on crops and pasture. Large armies of black caterpillars suddenly appear, often catching farmers unaware: the migratory moths arrive en masse and lay billions of eggs in a few days. This results in devastation of crops in the grass family, which includes staples such as maize, sorghum, millet, rice and wheat, as well as pasture. Outbreaks tend to occur during growing seasons following periods of drought and can have a devastating impact on food production.

In May/June 2008 outbreaks of armyworm were reported in 24 districts in Kenya – damaging 10,324 ha of crops and 41,435 ha of pasture. Between 2006 and 2009 Tanzania has recorded outbreaks on crops covering 233,000 ha. A major outbreak of armyworm occurred in Tanzania in December 2009, and soon after outbreaks also occurred in Kenya.

Impacts are therefore felt by both crop and livestock farmers. Current forecasting systems and control are seen as the responsibility of government - they are useful for national planning, but often don't help individual poor farmers. Neither centralized forecasting systems nor control based on the use of imported pesticides provide sufficiently early warning or safe and effective control. This may be because the government has insufficient capacity to respond, or the pesticide may be too expensive. The pesticides purchased for armyworm control also contribute to the build-up of potentially dangerous chemical stockpiles.

This Best Bet is establishing a system for the production, supply, distribution and marketing of Safe and Affordable Army Worm Control Tools (SAACO-Tools), including:

• a tool for local forecasting of outbreaks
• a cheap, safe, locally produced biological pesticide for controlling them

Research and development of these tools was funded by DFID and others as part of the RNRRS legacy. They have recently been validated and are now ready for commercialisation and widespread use.

Together the tools will reduce the devastating effect of armyworm outbreaks on food production. The system will supplement the centralised forecasting systems which currently do not meet the needs of the rural poor. It will also replace the use of imported chemical pesticides which, due to the high costs and environmental unacceptability, currently only meet the needs of around 30% of poor farmers. About 30% of districts in Kenya and Tanzania are susceptible to armyworm – estimated to total around 2.1 million households.

"Forecasting and monitoring of armyworm outbreaks is an integral part of the mandate of the government in an effort to control the pest and enhance food security" Joseph Ngetich Deputy director of agriculture, Plant protection services division, Ministry of Agriculture, Kenya

The community based armyworm forecasting enables farmers to make forecasts for their own village with over 80% accuracy. The trap costs and chemical attractants are expected to cost $14 a year. Community-based armyworm forecasting is a novel approach using technology already developed and validated in the field. Adult armyworm populations are monitored using a trap baited with a synthetic version of female sex pheromone. Because the monitoring is done locally farmers have more time to prepare for control or to seek help. One forecasting tool can cover around 200 ha.

The Best Bet control tool is SpexNPV, a non-toxic low-cost locally produced bio-pesticide. It is in fact a naturally occurring, highly infectious virus of armyworm that can rapidly wipe out outbreaks of the pest. Whilst the SpexNPV is naturally occurring it cannot be relied upon to arrive unaided/naturally, as it usually appears towards the end of an outbreak. The SpexNPV is harvested and sold to farmers in affordable 50-100 g bottles. This treatment is effective and is half the cost of chemical pesticides. It is non-toxic and requires no specialist safety gear and represents no danger from stockpiles, unlike with chemical pesticides. It is anticipated that it will cost around $5-6 per ha.

"Since forecasting at community level is so beneficial I would like to request that the government makes an effort to ensure that every village in Tanzania, that is prone to attack by armyworm, is given this facility so that they can predict outbreaks."

Rasul Abdulrahman - Armyworm community forecaster

'We are putting the necessary emphasis in terms of community based forecasting systems. We have seen it. It works and we are convinced it is the right way to go...'

Mohamed Muya - Permanent Secretary Agriculture, Tanzania