The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an insect native to the tropical and subtropical Americas that has recently spread to Africa, where it predominately attacks maize, sorghum and other plant species. Biological control is an environmentally friendly way of combatting the pest and contributes to an integrated pest management approach. In Africa, several trichogrammatid parasitoids and Telenomus remus Nixon (Hymenoptera: Platygastridae) have been found parasitizing eggs of the FAW. In Niger, the egg parasitoids encountered include Trichogrammatoidea sp. (Hymenoptera: Trichogrammatidae) and Telenomus remus Nixon. Parasitism of the FAW eggs by the two egg parasitoids was assessed in the laboratory, followed by field testing on sentinel eggs. In the laboratory, T. remus parasitized on average 78% of FAW eggs, compared to 25% for Trichogrammatoidea sp. Telenomus remus was able to parasitize egg masses that were fully covered with scales, while Trichogrammatoidea sp. parasitized only uncovered egg masses. On-farm releases of T. remus in sorghum fields caused up to 64% of FAW egg parasitism. Parasitized eggs yielded viable progeny, which can contribute to FAW egg parasitism build-up during the cropping season. Our findings lay the groundwork for the use of T. remus in augmentative releases against FAW in Africa.

In the absence of commercialized vaccines for most arboviruses, including dengue, chikungunya, and Zika, which are transmitted by Aedes aegypti, the management of vector populations to prevent disease transmission remains the cornerstone of arbovirus control strategies. Larviciding targets the early stages of the mosquito life cycle and subsequently reduces the capacity of adult population to transmit pathogens. Here, we report the susceptibility profile of Ae. aegypti larval populations from two West Africa cities, namely Niamey and Ouagadougou, to organophosphates larvicides. In Niamey, sampling was carried out using ovitraps at two sites, whereas in Ouagadougou, larvae were collected from three different types of larval containers at a single site. Temephos and fenitrothion were tested at six different concentrations each. Mosquito populations from Niamey and Ouagadougou were found susceptible to temephos and fenitrothion, with LD₅₀ < 0.015 mg/L and RR₅₀ < 5. However, Ae. aegypti populations from Ouagadougou showed reduced susceptibility to temephos compared to baseline data from 2016, as indicated by RR₅₀ values. This observation highlights the need for regular surveillance of larval susceptibility, as it may signal the emergence of temephos resistance in Ouagadougou. The acetylcholinesterase (AChE) mutation and the expression levels of metabolic genes Carboxy-/Cholinesterase (CCE) should be characterized to understand the molecular mechanisms underlying the observed phenotype response. Our results provide up-to-date data that could inform the potential deployment of these larvicides for the prevention and control of dengue and chikungunya outbreaks in Ouagadougou and Niamey.