The South American tomato pinworm, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) is a leafminer species currently considered as one of the major pests of fresh tomatoes around the world. The species settled in north Africa in 2007, before being observed in the entire continent. Widespread insecticide use has led to the emergence of resistant populations in South America and Europe, but no large-scale insecticide resistance assessment has been performed in Sub-Saharan Africa so far. In this study, we collected T. absoluta larvae from locations widely distributed in Burkina Faso, where the pest was first detected in 2016. Acute toxicity of the all available molecules in Burkina Faso was evaluated in the laboratory on F1 individuals, including acetamiprid, abamectin, spinosad, cypermethrin, chlorpyrifos, λ-cyhalothrin, deltamethrin, and Bacillus thuringiensis. No LC50 differences among T. absoluta populations were highlighted, except for Bacillus thuringiensis. Insects were still highly susceptible to abamectin [LC50 < 0.4 mg/L; Control failure likelihood (CFL) = −25%], spinosad (LC50 < 0.6 mg/L; CFL = 25%) and chlorpyrifos-ethyl (LC50 between 254 and 458 mg/L; CFL = −15%), but were less susceptible to acetamiprid (CFL ranging from 72% to 91%), cypermethrin (CFL = 80%), λ-cyhalothrin (CFL =79%), and deltamethrin (CFL ranging from 51% to 66%), with LC50 values for these insecticides ranging between 100 and 525 mg/L. Pending a proper communication strategy, we hope this work could help producers avoiding the most inefficient active substances.

Introduction. The fall armyworm Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) is a voracious and generalist insect pest native to America. It was first detected in West Africa in 2016 and rapidly spread across the continent. The indiscriminate use of chemical insecticides poses risks to human health and threatens the few natural enemies present in these environments. Despite the existence of alternative control measures in America (e.g. genetically modified maize), efforts are needed to develop environmentally friendly approaches that are affordable for smallholder farmers and compatible with the African context. Literature. In this literature review, we describe the potential of the available alternative controls methods which include cultural, physical, biological and semiochemical strategies. The potential of their association is discussed considering their cost-benefice balance and local economic and agricultural context. Conclusions. Several affordable mitigation options could be implemented rapidly, pending proper communication efforts, including (i) the promotion of indigenous natural enemies by promoting refuges and training smallholder farmers on their identification; (ii) cultural methods, mainly by planting directly after the main rainfalls, as well as performing intercropping and crop rotation; and (iii) the use of microbial biopesticides, and avoiding some of the already identified ineffective chemical insecticides.

La chenille légionnaire d'automne Spodoptera frugiperda (Lepidoptera: Noctuidae) est un ravageur vorace qui se nourrit principalement de céréales et autres cultures d'importance économique. Originaire d'Amérique, elle a récemment envahi les pays d'Afrique sub-saharienne où elle menace actuellement la sécurité alimentaire. Les connaissances sur ses ennemis naturels en Afrique sont limitées. Dans cette étude, nous avons cherché à identifier les arthropodes, les champignons et les nématodes entomopathogènes qui contrôlent naturellement ce ravageur au Burkina Faso. Des échantillonnages d'insectes, y compris des larves et des masses d'œufs, ont été réalisés dans 47 champs de maïs d'octobre 2019 à novembre 2020. Une vingtaine d'espèces de parasitoïdes, de prédateurs et de champignons entomopathogènes associés à la chenille légionnaire d'automne ont été identifiées. Le taux de parasitisme global était de 10,5 %. Les nématodes (Mermithidae) étaient les parasites les plus fréquents (73,2% des larves parasitées). Les parasitoïdes identifiés comprenaient des Hyménoptères [Coccygidium luteum (Brullé), Chelonus bifoveolatus (Szépligeti)] et des Diptères (Drino sp.). Les prédateurs comprenaient des Areneae et des insectes appartenant aux familles suivantes : Carabidae (Calleida sp.), Coccinellidae [Cheilomenes sulphurea (Olivier)], Forficulidae [Diaperasticus erythrocephalus (Olivier), Forficula senegalensis (Serville)], Formicidae [Pheidole megacephala (Fabricius) et autres], Mantidae, Pentatomidae et Reduviidae (Rhynocoris sp.). Les prédateurs les plus abondants étaient les Forficulidae (51%), Formicidae (15%) et Coccinellidae (13%). Nous préconisons le développement de la lutte biologique de conservation, car cette approche peut être simple et rentable pour contrôler ce ravageur.

Tuta absoluta est un micro-lépidoptère originaire d’Amérique du Sud et recensé au Burkina Faso depuis 2016. Ses larves creusent des galeries dans les feuilles et les fruits de la tomate. Grâce à des enquêtes détaillées réalisées auprès de 180 producteurs, nous avons évalué l’impact de ce ravageur sur la culture de tomates. Les cultivateurs produisent la tomate sur des superficies inférieures à ½ hectare. Tous ont démontré leur connaissance de T. absoluta et peuvent en décrire les symptômes. En moyenne, les producteurs estiment que cette mineuse leur fait subir des pertes de rendement comprises entre 45 et 70%, résultant en des pertes financières de 1 à 2 millions de Francs CFA par hectare. Près de 80% des producteurs n’ont recourt qu’aux produits phytopharmaceutiques, dont seulement 42% sont homologués pour la tomate. Quinze substances actives sont utilisées, dont l’emamectine benzoate, l’acétamipride et la cyperméthrine. La résistance des populations est telle que de nombreux producteurs abandonnent des parcelles à cause d’infestations incontrolables. Des méthodes alternatives sont parfois employées : destruction des plantes infestées, rotation de cultures, désherbage et biopesticides. Plusieurs producteurs pensent que l’invasion de cet insecte est indirectement la cause de conflits familiaux et de la baisse de leur niveau de vie.

The fall armyworm (Spodoptera frugiperda) is a worldwide maize pest originating from the American continent. It invaded Africa during 2016, causing important economic damages, forcing African countries to take urgent actions to tackle this new invasive pest. In Burkina Faso, several chemical insecticides were promoted, but farmers have quickly and repeatedly reported control failures. In this work, we collected seven fall armyworm populations in as many maize producing areas of Burkina Faso. Following the approved IRAC leaf bioassay protocole, we evaluated the susceptibility of third instar larvae to seven commercially available insecticide formulations, including various modes of action: methomyl and chlorpyriphos-ethyl (acetylcholinesterase inhibitors), deltamethrin and lambda-cyhalothrin (sodium channel modulators), emamectin benzoate and abamectin (chloride channel activators) and Bacillus thuringiensis (a microbial disruptor of insect midgut membranes). Lethal concentrations (LC50), resistance ratios (RR50) and relative toxicity were calculated for each population and active ingredient. LC50 values for all S. frugiperda populations were, in order of importance: emamectin benzoate (0.33-0.38 µg/l), methomyl (18-73 mg/l), abamectin (58-430 mg/l), chlorpyrifos-ethyl (199-377 mg/l), deltamethrin (70-541 mg/l) and lambda-cyhalothrin (268-895 mg/l). LC50 of the B. thuringiensis formulation ranged from 430 to 614 MIU/l. Lambdacyhalothrin was the least efficient of the tested chemical pesticides, and emamectin benzoate the most efficient (relative toxicity × 2,712,969). Methomyl (× 49), abamectin (× 5), deltamethrin (× 13), chlorpyriphos-ethyl (× 4) were also more toxic than lambda-cyhalothrin.Based on these results, we conclude that emamectin benzoate, methomyl and chlorpyriphosethyl insecticides are the most efficient for the control of the fall armyworm in Burkina Faso.We discuss the importance to implement a national-level resistance survey for this major pest, which would allow rapid and efficient adaptation of the control strategy.

The South American tomato pinworm, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is an economically important insect pest of tomatoes. Since its discovery in Burkina Faso in 2016, the use of synthetic insecticides was favored, with many cases of treatment failure. To explore alternative control methods, we conducted a screening of the 12 main tomato varieties produced in the country to test two hypotheses: (i) Some tomato varieties are less likely to attract gravid females and be used as oviposition site; (ii) Some varieties are unsuitable host plants as they allow slower development and lead to higher mortality. The varieties tested include RomaVF, KanonF1, Cobra 26 F1, FBT1, FBT2, FBT3, RaissaF1, JampacktF1, Mongal, Rio Grande, Tropimech, and Petomech. T. absoluta fitness was largely impacted by the tomato variety, especially egg incubation time and larval and pupal stage durations. As a result, the total T. absoluta life cycle was slower on Cobra 26 F1 and Kanon F1 (24.6 ± 1.8 and 25.8 ± 3.3 days, respectively) and faster on FBT1 and Rio grande (22.6 ± 3.0 and 22.8 ± 2.6 days, respectively). None of the varieties impacted the adult lifespan. All varieties were accepted as hosts by gravid females during multiple‐choice oviposition assays. The number of eggs laid per female was statistically similar among the varieties. We conclude that two varieties, Kanon F1 and Cobra 26 F1, have better abilities to slow T. absoluta development, limiting the number of generations while increasing the probability that natural enemies find and kill their prey.

Description of the subject. The fall armyworm Spodoptera frugiperda Smith has recently invaded sub-Saharan African countries where it causes significant losses to maize since 2016. Objectives. In this study, we examined farmers' knowledge of the fall armyworm, changes in pest management practices, and the safety of insecticide use by farmers since the recent invasion of the pest in Burkina Faso. Method. Data were collected through a survey of 197 maize farmers. Results. The majority of the farmers (96%) had experienced the fall armyworm invasion, mainly on maize, but also on sorghum and rice. Almost none of them (7%) used chemical insecticides to control maize pests before the arrival of the pest. Since then, 84% have used chemical insecticides, but various measures have also been implemented: cultural practices (48%) such as early planting, crop associations and fertilization; physical control (29%, i.e, handpicking, application of sand and ash) and applications of aqueous extracts of Azadirachta indica and Khaya senegalensis (12%). Most farmers do not use protective equipment when handling insecticides. Although they can name several natural enemies of the fall armyworm based on the photographs presented to them, they are generally unable to describe their beneficial role. Conclusions. We recommend evaluating the effectiveness of alternatives to chemical insecticides, publishing information on locally available insecticides that effectively control fall armyworm, and training farmers on proper pesticide application methods and natural enemy recognition.

Tuta absoluta (Lepidoptera: Gelechiidae) is a worldwide invasive insect species, considered a major pest of tomato. It has recently established in Burkina Faso, where chemical control remains the only affordable option to limit damages. Nesidiocoris tenuis (Hemiptera: Miridae) is commercialized as a biological agent to control this pest in other parts of the world. But very limited information exists on this predator in Burkina Faso. In this study, we first performed an insect survey in all agricultural regions areas of the country, and we found N. tenuis to be widely observed in all of them. Then, we performed two laboratory bioassays and demonstrated that all instars preyed on T. absoluta eggs, whether they were fed ad libitum or they had to actively forage for their prey. Because insecticide tolerant populations of T. absoluta were recently identified, we finally aimed at identifying agrochemicals that do not harm N. tenuis. We evaluated the toxicity of two synthetic insecticides, three bio‐bacterial insecticides and eight plant extracts, all being active ingredients available on the local market. Most of them (i.e., abamectin, emamectin benzoate, spinosad, spinetoram) were highly toxic for both T. absoluta and N. tenuis. In contrast, Bacillus thuringiensis var. Kurstaki, neem oil, Cleome viscosa (Asian spiderflower), Ocimum basilicum (Basil) and Cassia occidentalis (Coffee senna) were compatible with N. tenuis while still controlling T. absoluta. Based on our results, we recommend the application of Bacillus thuringiensis to both control T. absoluta and which does not compromise the maintenance of N. tenuis populations.