Evaluation of Quantitative and Qualitative Losses on Millet and White Rice in Storage Grains Caused by <i>Corcyra cephalonica</i>(Stainton) in Senegal

In Senegal, millet (Pennisetum glaucum (L.) R. Br.) and rice (Oryza sativa (L., 1753)) are the most widely consumed foods. This study is part of improving the conservation of these two cereals in Senegal by assessing the quantitative and qualitative losses caused by a lepidopteran, Corcyra cephalonica (Stainton) subservient to millet and rice stocks. For this purpose, samples of millet and rice from an area of the center of the groundnut basin (Diourbel) were collected, sterilized in the cold and infected with C. cephalonica eggs from the same locality. These infected samples were tracked during a development period of two successive generations. The samples were scrutinized before being infected and after a larval cycle of codling moth. The results showed that rice grains are richer in water (10.75% ± 0.4249%, on average) than millet (9.40% ± 0.3944%, on average) and the difference in rank is very significant (p-value = 0.0001 < 0.05). Moreover, the attack percentage on millet grains is three times higher (36.31% ± 25.18%) than rice (12.95% ± 6.69%) with a non-significant difference (p-value = 0.296 > 0.05). A similar trend is observed at the loss percentage, which is four times higher with millet grains (8.67% ± 5.07%) than rice (2.86% ± 2.75%) with a non-significant difference (p-value = 0.835 > 0.05). A multiple linear regression showed a generation effect on millet for the attack percentage and a generation and cereal effect for the percentage of weight loss on rice.

Diversity and Genetic Structuration of Populations of <i>Plutella xylostella</i>(Lepidoptera, Plutellidae), Cabbage Farming Destroyer in Senegal

Plutella xylostella, pointed out as the most dangerous destroyer of cabbage (Brassica olerarea), is a cosmopolitan species. In fact, owing to its large capacity of adaptation, P. xylestella colonizes any kind of area. This insect can bring about up to 90% of losses on cabbage farming. To control the insect, Senegalese farmers, very often, resort to high dose of chemical pesticides which are repetitively sprayed. The use of these chemical products gives rise to different varieties of resistant insects, which results in the emergence of different haplotypes between populations. It is in such a context that this study has been undertaken. Our objective is then to contribute to the knowledge of the genetic diversity of P. xylostella populations in Senegal. To hit the target, PCR- Sequencing method has been applied on samples from the five following localities: Diofior, Malika, Mboro, Santh Ndong, and Sebikotane. P. xylostella from Mboro is genetically different from the other populations. This fact could be due to a different way of using pesticides in this area vis-à-vis of the other localities. On the other hand, between populations of P. xylostella from Diofior, Malika, Santh Ndong, and Sebikotane, there is no significant genetic difference. In other respects, phylogenetic trees reveal the existence of two clades: one with individuals from Mboro and the other one with individuals from the other four localities. P. xylostella from Mboro distinguishes itself from other populations and then, can be regarded as a sub-population. Thus, the phylogenetic trees reveal the existence of two groups of P. xylostella in Senegal.