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.

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.