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Study of the effect of cultivation practices on the African rice gall midge : case of nitrogen fertilizers and rice plant spacing

Isaïe SIBOMANA student laureate

°1965 Rwanda
Agricultural engineer, Institut du développement rural, Université polytechnique de Bobo-Dioulasso, Burkina Faso, 1999

Etude de l'effet des pratiques culturales sur la cécidomyie africaine du riz : cas de la fumure azotée et des écartements entre les plants de riz

Isaïe Sibomana's study has quite a high relevance for sustainable development because it emphasizes the biological and cultivation aspects of integrated pest management in Burkinabe rice cultivation. The work is scientifically sound and well presented. The discussion is clear and convincing.
Rice is an extremely important crop in Burkina Faso, and the needs are only partly covered by local production. Insects, in particular the african rice gall midge, constitute an important element influencing local yield losses.
Isaïe Sibomana studied the role some aspects of cultivation play in the control over the midges by assessing the impact of nitrogen fertilization on the one hand, and plant spacing on the other hand. In a rigorous experimental setup, he analysed the plants' response to variations of these two factors (plant growth, numbers of grains per plant, weight of 1000 grains). He also studied the insects' reponse (number of galls, larvae, pupae per tuft; number of parasites of the fly).
The results of this work suggest a moderate effect of the nitrogen treatment and a very strong impact of the density of cultivation on plant growth. Plant growth is proportionate to plant spacing. The highest populations of the gall midge are found at the highest nitrogen level and at the highest plant density. Parasitism of the gall midges by two species of wasps, which reached 60% for one parasite species and 16% for the other, did not depend on the nitrogen level but increased with plant density. Finally, the yield (in terms of grains per panicle) increased with the nitrogen level as well as with the plant spacing. The average weight of the grains was not affected by the treatments.

report by Prof. Dr. Jean-Claude Grégoire, Laboratory for animal and cellular biology, Université Libre de Bruxelles, Belgium