Part 1.4

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A SUMMARY OF THE MAJOR RESEARCH FINDINGS ON THE INTEGRATED CONTROL OF MAIZE STORAGE PESTS AT THE FACULTY OF AGRONOMY, BENIN

D.K. KOSSOU

National University of Benin, Faculty of Agronomy, Cotonou, Benin

Introduction

The integrated control of maize store pests on the one hand, and the diagnosis of the future development of post-harvest systems in Sub-Saharan Africa on the other hand, cannot be done without a knowledge, however little, of the current state of the activities implemented by the different agencies, public or private training and research institutions, Non-Governmental-Organisations and farmers, etc.

Summary of results

The objectives of the research on post-harvest systems initiated at the Faculty of Agronomical Sciences of the University of Benin in mid 1980 are as follows:

a greater knowledge of the ecosystem of cosmopolitan pests found in grains and their derivatives;

*	a greater understanding of how major pests adapt to the different states of grains being preserved (cobs and grains), especially since maize is more frequently stored in cobs in the South;
*	an analysis of the storage ecosystem with special reference to the basic structures (components) and their effect on pest infestation and the state of the stocked product; a more judicious application of insecticides through the development of indigenous methods especially local plants and their different effects (insecticides, insect repellents, ovicides, lavicides) in the protection of the environment, and,
*	the development of the approaches used in the integrated pest control system using different resistant methods, biological control, rational application of protective products, sanitation, and other good stock preservation methods.

The various studies were not carried out by lecturers in the Faculty of Agronomical Sciences alone; some particular aspects relating to genetics and improvement, and the analysis of components of plants could only be accomplished with the help of foreign Universities or international institutions such as UAW, GTZ, IITA etc. The contribution of the INRAB team through the Ina and Niaouli Centres must also be acknowledged.

At this point in time, a set of technical information is available and can be considered to adequately represent the major components in the implementation of the programmes on the integrated control of major maize stock pests. If the recommended procedure is systematically observed to reduce the problems, then the following points can be mentioned:

*	The choice of variety to plant is very important. Husk cover characteristics like the tightness of husks, the extension of the leaves of the husks, and the compression of the leaves of the husks are features of most of the local varieties that may be integrated into the improved varieties with high yield to ensure better products. It is only at this stage that the modifications in the area of eating qualities, moisture, etc. desired by the beneficiaries can be tackled (Kossou et al., 1993; Kling et al.,1995).
*	Traditionally, harvesting is done when the cob droops from the mother plant in the dry season. At this time, the farmers depend mainly on solar energy to reduce the humidity of the grains in the farm by between 18 and 20% (moisture content). This results in early infestation by insects, birds, rodents, and increased moisture. Different varieties, including local and improved varieties are evaluated for their adaptability to indigenous practices that are more popular in the southern part of Benin. The various before mentioned characteristics, coupled with the extreme curve of the leaves of the husks in the extension zone, helped reduce damage level, especially those resulting from the activities of insects and moisture (Omontecho, 1986; Kossou et al., 1993; Kossou et al., 1994).
*	The drying process, an indispensable part of the physiological and physico-chemical retardation system responsible for the alteration of the grain through the reduction of water retention level, cannot be ignored in the harvesting process of local communities in the south where severe bimodal climatic conditions occur each year. Nor can this reality be ignored in the design of the storage/preservation space. The research is mainly concerned with the relative variation of temperature and humidity and the rapid drying of the cobs. The difficulties arise mainly from the differences recorded in the same type of storage space and the different types that exist. Linked to that is the disappearance of the most popular materials which are sometimes best adapted to deal with the Bostichidae, currently a subject of major concern (Affognon, 1989; Djomamou, 1990; Kossou, 1992; Kossou et al., 1993). Ealeis guineensis Jacq.(Palmaceae) and Holarrhena floribunda (G Don) Dur and Schinz (Apocynaceae) which are least tolerated by Prostephanus truncatus (Horn), recorded a pronounced disparity in flora level. No doubt this is due to the fact that wood is used for other purposes as well, and a substantial quantity is required. However, a considerable amount of granary construction materials has recently been collected from the south in order to create alternative protection methods or substitute formulae. This falls within the Agricultural Sector Development Assistance Programme being realised with the support of INRAB.

In all the cases, the structural system in southern Benin is associated both with drying and stocking operations. The results are therefore expected to come up with models:

1.	that are acceptable to the beneficiaries;
2.	that are conform to the drying principle;
3.	that are adapted to the stock management system of the targeted group;
4.	whose cost/benefit analysis is profitable to the beneficiaries.

Stocking is done in the three states of storage practised: undehusked cobs, dehusked cobs and grains. However, the state in which the cobs are more frequently stored by the rural community and those recommended by Extension services received more attention in the research in order to provide explanations on maize storage in the dehusked state that will be relevant to almost all the farmers in the south. The results of the different studies show that the resistance of the unshelled maize to the Sitophilus zeamais Mots. seem to be dependent on three factors (Kossou et al., 1992):

^1.	the reduction of the oviposition, since the preferred zone is not displayed by the grain when it is fixed in the cob;
^2.	increase in the development period because of the new developments less nutritive zone of the 1^st stage larva;
^3.	further increase of the development period due to the fact that the first generation insects find it difficult to come out of the grain.

These factors that contribute to the reduction of the population density and infestation often noted in the traditional storage system whether the cobs are dehusked or not, deserve further study because this storage state will remain the reality of the rural community in the southern zone for a long time yet.

The origin of the problems of the different stock protection methods can be found here. Appropriate methods should be sought based on indigenous methods. Many research works have been carried out since 1985 in order to obtain more knowledge on the use of plants with biological insecticide qualities. Some of the plant extracts or the dry powdery state of these components were tested in order to preserve maize stocks against such major insects as Sitophilus sp. and P. truncatus. Out of the more than ten plants evaluated, Neem extract (Azadirachta indica A Juss) on Sitophilus sp. and Clausena anisata (Willd) on P. truncatus seem to display the highest level of toxicity for preventive control. But the short period of effectiveness makes treatment necessary after two months in storage. In the approach using Neem products to protect maize in farmers’ conditions, the results require co-operation between participating farmers, a development that augurs well as actions aimed at the development of oil production units may eventually assume great importance (KOSSOU and SANNI, unpublished).

The details of all these research activities were used in the First Colloquium of REARB, OAU/IAPSC on the integrated control approach which took place in Lomé, Togo between the 10th and the 14th of February 1997 (Kossou, 1997).

The other elements of the post-harvest system are being handled by other Departments of the Faculty, especially marketing, processing and consumption.

However, it is important to emphasise that P. truncatus was identified in Benin in 1984 in the dry tubers of yam collected from Dantokpa market (Kossou, 1987). In earlier research carried out on the susceptibility of bostrichids in the different states of cassava and yam tubers, variations were noted depending on the processing method applied. Soaking in hot water or brief boiling as in the yam-chips manufacturing process significantly reduced their susceptibility to bostrichids (Kossou, 1988).

Conclusion

In view of the developments in the post-harvest sector of Sub-Saharan Africa, the achievements so far must be evaluated, information must be compiled on the different problems of the sector, and these must be considered in their own environment, and the whole system analysed thoroughly by involving all the stakeholders. The identification and implementation of the activities must be based on the priorities of the beneficiaries.

References

Affognon, H., 1989.
	Susceptibilité des matériaux végétaux de construction des greniers traditionnels dans le Mono face aux attaques de Prostephanus truncatus Horn (Coleoptera: Bostrichidae). Mémoire d’Ingénieur Agronome, Université Nationale du Bénin.
Djomamou, B.N., 1990.
	Problèmes du stockage traditionnel du maïs dans la Province du Mono. Mémoire d’Ingénieur Agronome, Université Nationale du Bénin.
Kling, J.C., Yallou, C.G., Kossou, K.D., Okoruwa, A.E. and Akintunde, A.O., 1995.
	Development of a high yielding maize variety with good dry milling and storage properties in Benin. Paper presented at the Postharvest Technology and Commodity Marketing Conference, Accra, Ghana, 27-29 November 1995.
Kossou, K.D., 1987.
	Un nouveau déprédateur dans le système post-récolte de la République du Bénin: Prostephanus truncatus (Horn) (Coleoptera; Bostrichidae). Carrefour de la Recherche 2:1-11.
Kossou, K.D., 1988.
	Divers formes de cossettes de racine et tubercule et leur sensibilité aux Bostrichidae Carrefour de la Recherche 4: 1-19.
Kossou, K.D., 1992.
	Sensibilité des bois de construction des greniers traditionnels aux attaques de Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). Insect Science and its Application 13(3): 435-439.
Kossou, K.D., Bosque-Pérez, N.A., and Mareck, J.H., 1992.
	Effets of shelling maize cobs on the oviposition and development of Sitophilus zeamais Motschulsky. Journal of stored Product Research 29(4): 333-343.
Kossou, K.D., Mareck, J.H., and Bosque-Pérez, N.A., 1993.
	Comparison of improved and local maize varieties in the Republic of Benin with emphasis on susceptibility to Sitophilus zeamais Motschulsky. Journal of stored Product Research 29(4): 333-33.
Omontecho, C.A., 1986.
	Caractéristiques phénologiques et physiques et sensibilité de quelques variétés de maïs au Sitophilus zeamais Motsch. Mémoire d’Ingénieur Agronome, Université Nationale du Bénin.