Laboratory and Greenhouse Evaluation of Melia volkensii Extracts for Potency against African Sweet Potato Weevil, Cylas puncticollis, and Fall Armyworm, Spodoptera frugiperda

Victor Jaoko,Pierfrancesco Motti,Sven Mangelinckx,Simon Backx,Titus Magomere,Guy Smagghe,Jackson Mulatya,Jan Vandenabeele,Stefaan P O Werbrouck,Florence Olubayo,Clauvis Nji Tizi Taning

doi:10.3390/agronomy11101994

Victor Jaoko, Pierfrancesco Motti + Show 9 more

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https://doi.org/10.3390/agronomy11101994

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The African sweet potato weevil, Cylas puncticollis, and fall armyworm, Spodoptera frugiperda, are insect pests of economic importance that have a negative impact on sweet potato and maize production, respectively. In this study, we aimed to evaluate the potential of Melia volkensii extracts to protect sweet potato and maize plants against damage by both insect pests. We evaluated extracts from the bark, leaves, pulp and nuts of Melia volkensii for antifeedant activity against C. puncticollis and S. exigua (used as a substitute for S. frugiperda), under laboratory conditions. Interestingly, extracts of all plant parts showed antifeedant activity. These results led us to investigate the effectiveness of nut and pulp extracts to protect sweet potato and maize crops in greenhouse conditions. Against C. puncticollis, the sweet potato plants treated with nut extracts showed the lowest tuber damage (18%) when compared to pulp extracts (30%), positive control (33%) and negative control (76%). Nut extracts, pulp extracts and positive control reduced maize leaf and whorl damage by S. frugiperda compared to the negative control. Altogether, this study highlights the potential of M. volkensii extracts and their application in integrated insect pest management

Highlights

Insect control products of plant origin could offer more sustainable alternatives to synthetic insecticides because they have low mammalian toxicity and low persistence in the environment [1]
The focus of our study was on Melia volkensii, a drought-tolerant, fast-growing tropical tree species that grows in semi-arid areas of East Africa that is widely used in folk medicine for the treatment of various illnesses, such as diarrhea, pain and skin rashes [2,3,4]
Biopesticides such as azadirachtin and spinosad have been evaluated for their efficacy against the sweet potato weevils in the laboratory, but no studies have been reported on field trials [20]

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Insect control products of plant origin could offer more sustainable alternatives to synthetic insecticides because they have low mammalian toxicity and low persistence in the environment [1]. M. volkensii seed kernel extracts have shown antifeedant and growth inhibition activity against several insect pests [7,8,9,10]. Findings of previous studies and indigenous knowledge on M. volkensii makes this tree an interesting candidate for exploitation as a potential source of insect control products against insect pests of economic importance in Africa. Significant sweet potato damage and economic losses are caused by C. puncticollis which oviposit in the vines and tubers [10]. These weevils cause up to 100% yield loss [12,13,14], and the damage from weevils continues to increase during storage [15]. Biopesticides such as azadirachtin and spinosad have been evaluated for their efficacy against the sweet potato weevils in the laboratory, but no studies have been reported on field trials [20]

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