Small farmers in Africa in particular have always been faced with post-harvest losses, storage losses of maize making up a considerable percentage. Centuries of selection of tolerant varieties and development of appropriate store structures, storage methods and specific stored product protectants and procedures have contributed to keeping losses within tolerable limits. However, greater agricultural intensification in Africa has also lead to higher post-harvest losses. The changes have mainly been due to the "Green Revolution" with its high-yield varieties, which were not selected with regard to storability or tolerance to storage pests. Consequently, traditional post-harvest systems were no longer adequately efficient in many places, and measures were increasingly taken to adapt them to the new conditions.
The GTZ's post-harvest protection projects tackled post-harvest issues initially at the technical level.
Problem analysis
To establish a basis for further steps, situation analyses in the post-harvest sector were carried out in numerous countries, chiefly examining issues of grain storage at farm level. A variety of topics were tackled through laboratory tests, field trials and surveys carried out by the field offices of the supraregional GTZ projects in Costa Rica, Ghana, Malawi, Tanzania and Togo. The findings obtained were the basis for elaborating solutions and recommendations for extension work.
Development of post-harvest protection techniques
A considerable number of new post-harvest protection techniques have been developed, especially in the field offices and projects in the partner countries. These techniques address the improvement of existing stores and traditional storage methods, particularly in relation to storage hygiene and other preventive measures, but have also included novel methods that usefully complement the existing post-harvest systems. They are documented in numerous reports, doctoral theses, technical publications and extension materials
(Annex I). Where it is necessary to recommend the use of synthetic stored product protectants, which is unavoidable in cases of severe pest infestation, care has been taken to provide information on user and consumer safety in addition to information on the potential effects on target organisms.
Training and extension
The measures thus developed were implemented by means of intensive international training efforts, in which more than two thousand multipliers in the post-harvest sector received training in some hundred seminars, courses and workshops. These multipliers disseminated their knowledge at numerous events carried out at the national level. However, it is difficult to make precise statements on the contribution these multipliers have been able to make to improving the situation of farmers under the given framework conditions. In the period from 1994 to 1997, ca. 12,000 copies of the extension documents listed in Annex I were ordered by our partner experts.
In bilateral projects in particular, post-harvest protection is particularly linked directly to rural extension work. It is partly attributable to the intensive project work that post-harvest issues have received priority status in national development policies in a number of countries (e.g. Ghana and Tanzania).
Documentation
The results of the post-harvest work have been documented in several books, doctoral theses, technical publications and extension brochures and leaflets (Annex I).
Information related to post-harvest systems is also available on the internet from the web sites of the GTZ <https://www.gtz.de/post_harvest>
and of FAO <https://www.fao.org/inpho>.
The accidental introduction of the Larger Grain Borer (Prostephanus truncatus) (LGB) to Tanzania and Togo at the end of the 1970s created a new threat to farm-level storage. This wood borer from Central America is a facultative storage pest. It causes damage to stored maize and dried cassava chips on a scale that had not previously been experienced. The BMZ reacted in 1984 to the new situation by establishing a supraregional project for the integrated biological control of the Larger Grain Borer. The project developed to implementation maturity the use of the predatory beetle Teretriosoma nigrescens (Tn), a natural antagonist of the LGB from its Central American home.
Upon request by the partner authorities in Togo, and after appropriate preliminary studies and in consultation with FAO and other international agencies, the biological control technique was implemented in 1991 with the first releases of the antagonist. In the following years, Tn was released in other countries affected by the LGB (Annex II). A number of research institutes and services were involved in complementary research work and in the releases. These included the Kenya Agricultural Research Institute (KARI), the Natural Resources Institute (NRI), the International Institute of Biological Control (IIBC), the International Institute of Tropical Agriculture (IITA) and national plant protection services such as the Service de Protection des Végétaux in Togo and Benin.
The spread of Tn in the countries stated in Annex II was implemented in cooperation with the IITA and the national services.