Citation: Issa, K.A.; Wosula, E.N.; Stephano, F.; Legg, J.P. Evaluation of the Efficacy of Flupyradifurone against Bemisia tabaci on Cassava in Tanzania. Insects 2022, 13, 920. https://doi.org/10.3390/ insects13100920 Received: 13 September 2022 Accepted: 7 October 2022 Published: 12 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). insects Article Evaluation of the Efficacy of Flupyradifurone against Bemisia tabaci on Cassava in Tanzania Khamis A. Issa 1 , Everlyne N. Wosula 1 , Flora Stephano 2 and James P. Legg 1, * 1 International Institute of Tropical Agriculture, Dar es Salaam P.O. Box 34441, Tanzania 2 Department of Zoology and Wildlife Conservation, University of Dar es Salaam, Dar es Salaam P.O. Box 35064, Tanzania * Correspondence: j.legg@cgiar.org; Tel.: +255-22700092 Simple Summary: Cassava-colonizing Bemisia tabaci whitefly negatively impact cassava production in sub-Saharan Africa through transmission of viruses that cause cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). This study evaluated the efficacy of a novel insecticide flupyradifurone against this whitefly pest through standard spraying and cutting dip methods. The results from the laboratory, screenhouse and field experiments consistently showed flupyradifurone is effective at reducing whiteflies compared to control treatments. A single cutting dip using this insecticide was highly effective at reducing whiteflies under field conditions and, therefore, should be considered as an alternative to insecticide spraying in cassava systems. Additionally, whiteflies were least abundant during the long rainy season (Masika) and on cassava variety Mkuranga1. Abstract: A novel butenolide insecticide—flupyradifurone (Sivanto SL 200)—was evaluated for efficacy against cassava-colonizing Bemisia tabaci whitefly under laboratory, screenhouse and field conditions. LC50 values from leaf disc spray assays were comparable for both flupyradifurone (12.7 g a.i/100 L) and imidacloprid (12.6 g a.i/100 L). Both insecticides caused high levels of adult whitefly mortality in leaf disc and leaf dip assays when compared to untreated controls. In screenhouse-based trials, longer soaking (60 min) with flupyradifurone or imidacloprid was more effective than shorter soaking durations (15 or 30 min). In field spraying experiments, flupyradi- furone significantly reduced whiteflies, and both insecticides demonstrated powerful knockdown effects on whitefly adult abundances over a period up to 24 h. Single cutting dip application of flupyradifurone reduced whitefly adult abundance by 2 to 6 times, and nymphs by 2 to 13 times. Lower whitefly abundances resulting from insecticide application reduced the incidence of CMD or CBSD. In addition, in field experiments, whiteflies were fewer during the long rainy season (Masika) and on cassava variety Mkuranga1. The findings from this study demonstrate that cutting dips with flupyradifurone could be incorporated as a management tactic against cassava whiteflies. This would ideally be combined in an IPM strategy with other cassava virus and virus vector management tactics including host-plant resistance, phytosanitation and the use of clean seed. Keywords: flupyradifurone; Bemisia tabaci; cutting dip; CMD; CBSD; IPM 1. Introduction The whitefly Bemisia tabaci (Gennadius) (Hemiptera, Aleyrodidae), is one of the most economically damaging pest species of crop plants in Africa. It causes physical damage as well as transmitting many plant viruses [1,2]. Besides its importance with regard to cassava, the species complex is well known across the world as one of the most important global pests and has been reported on more than 1000 species belonging to over 100 plant families [3]. Cassava (Manihot esculenta Crantz) is an important subsistence crop throughout much of sub-Saharan African and is perceived as Africa’s future food security hope, due to its Insects 2022, 13, 920. https://doi.org/10.3390/insects13100920 https://www.mdpi.com/journal/insects