Effect of Transplanting Zones and Dates on Pre-imaginal Populations, Parasitism and Attacks of Major Insect Pests of Rice on the Rice-Growing Area of la Vallée du Kou (Bobo-Dioulasso)

Abstract

Lepidopterous stem borers cause extensive damage in irrigated rice in Burkina Faso and regularly compromise the harvest of the dry season rice in the rice-growing area of la Vallée du Kou in western Burkina Faso. Yield of losses of 40% were observe during the dry season. The study conducted during the wet season in 2015 examined the effects of areas and of transplanting dates on the evolution of population of stem borer's damage and of parasitism. Rice irrigation area of la Vallée du Kou was divided into three areas within which 12 farmers were selected on the basis of three dates of transplanting rice; they were total 36 for the days three transplanting dates. According to agronomic evaluation, the transplantation dates are influence by the number of tillers and by the number of panicles. The maximum average number of tillers was observed in the second area within the first date of transplantation. Otherwise the second area and the second date recorded the highest number of panicles. Entomological observations were carried on every 7 days from the 21 th day to 91 th day after rice transplanting in each of the 36 fields. Late transplanting (August) are the most exposed to Orseolia oryzivora attacks. The genus Chilo spp, Maliarpha and Diopsis spp were the most important pests in rice plants on the perimeter of la Vallée du Kou. Periods of greatest damage were observed in tillering. They were responsible for the deadhearts damage, for white panicles and for the highest rates. These damages were recorded during the first date of rice transplanting. Parasitism associated with the genus Chilo was observed in the first transplanting date. The hectare average yields were most important in the second transplanting date of within the third area. These results on the pre-imaginal populations are important data. These data can be taken into account to improve the development of a strategy to fight against the major insect pests of rice plants. All these elements are linked to the climatic variations.