Storage trials in Zimbabwe found diatomaceous
earths (DE) offered an alternative to organophosphate insecticides
and are effective in controlling post-harvest insect pests in maize,
sorghum and cowpeas stored for >8 months, enabling households
to increase their food security and control over grain sales.
This project will verify these findings under semi-arid conditions
in Tanzania where producers have constantly prioritised storage
losses, and where the devastating larger grain borer (Prostephanus
truncatus) is endemic.
Local sources of DEs are being evaluated for their potential as
sustainable low cost sources of DE.
New knowledge will be promoted amongst intermediary and end-users
in forms they can utilise and adapt, building on the multiple information
networks used by the respective user groups.
The project flyer [PDF, 321kb]
provides an overview of the project.
Background to the current project
The study of diatomaceous earths (DE) as grain protectants for
small-scale producers began in Zimbabwe in 1998. Producers were
expressing a need for a relatively cheap and safe method of storage
insect control. DEs offer safer alternatives to synthetic chemicals,
but information on their efficacy under tropical small-scale farming
conditions was lacking. The initial storage trials in Zimbabwe (from
1998 -2000) used two commercially available DE products Protect-It®
and Dryacide®. Both of these DEs gave significant protection
against insect damage when admixed with farm stored maize, sorghum
and cowpeas for periods of 40 weeks and were as effective as Actellic
Super dust. However, efficacy of these DEs is closely linked to
the application rates and differs between commodities, locations
and insect pests. Details of these trials can be found in two
publications.
In 1999 the Crop Post Harvest
Programme (CPHP) funded a regional East African workshop in
Dar Es Salaam to assess farmers strategies for coping with the Larger
Grain Borer. The main message to come out of this workshop was that
farmers wanted alternatives to organophosphates for grain protection
so that they had options to choose from. Conventional insecticides
are often unavailable when needed, adulterated, of poor quality,
expensive and many farmers are afraid to use synthetic chemicals
on their stored food because they are inherently poisonous.
Following the workshop, Mr Riwa of the Ministry
of Agriculture and Food Security contacted NRI
to discuss the potential for the use of diatomaceous earths (DEs)
as grain protectants and the trials that we were conducting in Zimbabwe
in collaboration with the University
of Zimbabwe and the Institute of Agricultural Engineering. These
trials had found that DEs were effective in controlling post-harvest
insect pests in maize, sorghum and cowpeas stored for >8 months
under small-scale farmer conditions in Zimbabwe and offered an acceptable
alternative to the locally recommended insecticide, Actellic Super
Dust (ASD).
The existing evidence suggested that was potential for DEs to be
used in Tanzania to provide an alternative option for farmers in
the battle against LGB. We submitted an outline proposal to the
DFID Crop Post Harvest
Programme (CPHP) in April 2000. The CPHP Project Advisory Committee
were keen to fund the work, but were short of funds, so decided
to release limited funds to enable the full project proposal to
be collaboratively developed during a workshop in Shinyanga in August
2001.
At this workshop, participants related how farmers constantly mentioned
the threat posed by storage pest damage, to NGO staff and other
field workers and that the adulteration of Actellic Super dust had
reached such a serious scale in Tanzania (one farmer in Shinyanga
region actually managed to breed storage insects in what had been
sold to him as pesticide). The scale of damage caused by LGB and
the widespread adulteration of pesticides had made stored product
pest damage a political issue and parliamentary members had been
asking the Ministry of Agriculture what they were doing about this
problem. In June 2002, the project was funded and storage
trials were set up in three regions of Tanzania, Dodoma, Manyara
(formerly in Arusha) and Shinyanga.
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