Since chemical insecticides favor the emergence of resistance and have disastrous consequences for the environment, we became interested in an alternative control method against Spodoptera frugiperda, more respectful for the environment. We therefore evaluated the effectiveness of the bio-insecticidal effects of plants extracts and oil of castor against the fall armyworm in the laboratory. The laboratory bioassays consisted of evaluating the toxicity of the castor plants extracts and oil by contact and ingestion on fourth instar larvae of Spodoptera frugiperda using a leaf dipping method. It emerges from this study that the mortality of the larvae treated with the bio-insecticide and the control solution varies significantly and that the mortality rate was 100% for dose 1; 85% for dose 2 and 70% for dose 3. The mortality rate for the control solution is 10%. These results testify to the good larvicidal activity of the organic insecticide based on oil, leaves and unripe seeds of castor bean on the fall armyworm.
The oriental fruit fly, Bactrocera dorsalis, is one of the most destructive pests of tropical and subtropical fruit crops. The aim of this study was to assess the effect of 8 fruit species on oviposition preference and the offspring performance of B. dorsalis.Total soluble solids and pH of fruits were determined by using respectively a refractometer and pH meter.The oviposition preference was evaluated in choice and nochoice tests respectively inside1 by 0.6 by 0.6 m and 30 by 30 by 30 cm cages at laboratory conditions.The offspring performance was assessed by infesting the fruits with freshly laid eggs and followed until the emergence of adults.The values of total soluble solids content werevaried from 4.18 ± 0.99 (tomato) to 14.11 ± 0.99 (mango) ° Brix. The highest pH value was obtained on the papaya (5.61 ± 0.08) while the lemon was the most acidic fruit with a pH of 2.47 ± 0.08. The oviposition preference results revealed that papaya and mango were the most preferred hosts by B. dorsalis among tested fruits in choice and no-choice tests. However lemon was the least preferred fruit in this study.Mango seems to be the most favorable fruit for the development of B. dorsalis with a shorter development time (18.68 ± 0.61 days) after the papaya (17.68 ± 0.61 days) and a higher percentage of eggs survival to puparia (67.83 ± 8.11%) as compared to other fruits. However lemon was the unfavorable fruit for offspring survival of B. dorsalis, with a longer development time (22.16 ± 0.61 days) and a lower percentage of eggs survival to puparia (19.09 ± 11%) as compared to other fruits.
In order to measure the impact of a number of plants on the development of Spodoptera frugiperda, we carried out a comparative study on the biology of the fall armyworm using various food sources (millet, maize, sorghum, peanut, cowpea and artificial diet). When fed with cowpea and peanuts leaves, larval development was longer (21.46 ± 0.42 and 18.93 ± 0.18 days respectively). In contrast, adult stage duration became shorter when the larvae were fed with maize leaves and peanut (2.86 ± 0.21 and 3.33 ± 0.21, respectively). Similarly, the pupal development was longer when the larvae fed on peanut leaves and artificial diet (9.26 ± 0.11 and 9.40 ± 0.16 days, respectively), compared to the pupae whose larvae fed on maize, millet, sorghum and cowpea (8.46 ± 0.13; 8.40 ± 0.13; 8.13 ± 0.9; 8.93 ± 0.20 days, respectively). As for the adult stage, the duration is shorter when the larvae are fed with cowpea leaves (2.86 ± 0.21 days) and Peanut (3.33 ± 0.21days).
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