UN Division for Sustainable Development

Case Study Detail Record

Organization type:	Government

Name of Ministry/Agency:	German Federal Ministry for Economic Cooperation and Development (BMZ), International Centre of Insect Physiology and Ecology (ICIPE)

Country:	Germany

Name of Focal Point:	Dr. B. Löhr, International Centre of Insect Physiology and Ecology (ICIPE) P.

Initiative Title:	Biocontrol-based IPM for the Diamondback moth (Plutella xylostella), Eastern and Southern Africa

Internet links:	http://\\faoext06\FTP_Waicent\SD\SDA\SDAR\sard\English GP\EN GP Africa\Biocontrol_diamondbackmoth_Africa.pdf International Centre of Insect Physiology and Ecology http://www.icipe.org

Scope:	Regional: - Africa

Status:	Completed

Timeframe:	Start: 2004 End: 2007

Lead Institution:	International Centre of Insect Physiology and Ecology (ICIPE)

Stakeholders/Partners:	German Federal Ministry for Economic Cooperation and Development (BMZ)

Relevent issues:	- Environmentally sound pest control

Objectives/Challenges:

Cabbage is one of the most important vegetables grown in East Africa. It provides necessary dietary vitamins and minerals in a maize-based diet and generates substantial income for the producers and other agents involved in the marketing system, thus alleviating poverty and creating employment.
However, it is increasingly more prone to serious damage by the Plutella xylostella L., diamond back moth (DBM) often causing a complete loss of the crop. DBM also reduces marketabillity by contamination of the heads with larvae or frass. Synthetic pesticides are the major control method. The use of synthetic pesticides often leads to serious environmental problems besides
affecting the health of users and consumers. They also eliminate the natural enemies of DBM, creating the need for more pesticides, increasing production costs, and the development of insecticide resistance. An important alternative to synthetic pesticides is biological control, which avoids the environmental and human health costs.

Lessons Learned:

In spite of long-lasting efforts to improve DBM management through
biological means, long-term studies of the impact of its parasitoids are scarce. In many biological control projects, very little or no information is available about the existence and role of indigenous natural enemies or, more important in the times of discussions about the importance of biodiversity, the fate of indigenous natural enemies after introduction and
release of a supposedly superior competitor. In this project, observations on DBM and the local natural enemy population were made fifteen months prior to and three years after release. While the displacement of indigenous parasitoids was almost complete in cultivated cabbage, they persisted on wild crucifers which grow in abundance in the surroundings of cultivated fields. This is an important aspect as other pests may require pesticide use and
could thus eliminate the parasitoids locally. Rapid recolonization by parasitoids is made easy from the wild crucifers and this stabilizes the system considerably.
Most farmers in the pilot release areas and many others in other
growing areas have abandoned pesticide application against DBM.
Preliminary data indicate that the cost of pesticides used in cabbage production was reduced by about 60%. A large-scale study to confirm this is under way.
There was a considerable reduction in DBM numbers at the pilot
sites, starting from already three months after release. Numbers continued to decline steadily for the three after-release years. Similarly, the percentage of attacked plants declined in the three years after release, resulting in an abatement of crop losses and an increase in economic returns. This has been observed everywhere after the release of both D. semiclausum and C. plutellae. The parasitoids have reduced production costs by 10-15%, losses by 15 (rainy season) to up to 80% (dry season) and allows farmers to take advantage of higher prices during dry seasons.

Policy Options:

The technology is suitable for many more African countries and can be implemented at relatively little additional costs in case new funding can be mobilized.

Summary:

Observations on DBM and indigenous natural enemy population dynamics and pest damage were conducted, including taxonomic studies through molecular techniques. A complete inventory of these indigenous natural enemies was made, followed by an assessment of their effectiveness against DBM. This evaluation, however, failed to identify a specific and effective DBM parasitoid, and a decision was made to introduce Diadegma semiclausum, a solitary internal parasitoid with a long and successful history in the control of the pest in the highlands of Asia. Prior to the pilot release of the parasitoid, NARES extension staff were trained in data collection and the participation of farmers in release activities was ensured. The releases were conducted at two different sites in the highlands of Kenya and sampling was conducted regularly on the control
fields (fifteen farmer-managed farms).
Following the pilot release and studies of the impact of D. semiclausum, large scale releases were conducted in Kenya, Uganda and Tanzania. A second biocontrol agent for hot and dry areas, Cotesia plutellae, also a solitary internal parasitoid, was studied for three years in South Africa and then introduced. This species was released in Uganda and Kenya.