Indoor residual spraying of experimental huts in Cameroon highlights the potential of Fludora® Fusion to control wild pyrethroid-resistant malaria vectors.

Elevated resistance to pyrethroids in major malaria vectors has led to the introduction of novel insecticides including neonicotinoids. There is a fear that efficacy of these new insecticides could be impacted by cross-resistance mechanisms from metabolic resistance to pyrethroids. In this study, after evaluating the resistance to deltamethrin, clothianidin and mixture of clothianidin + deltamethrin in the lab using CDC bottle assays, the efficacy of the new IRS formulation Fludora® Fusion was tested in comparison to clothianidin and deltamethrin applied alone using experimental hut trials against wild free-flying pyrethroid-resistant Anopheles funestus from Elende and field An. gambiae collected from Nkolondom reared in the lab and released in the huts. Additionally, cone tests on the treated walls were performed each month for a period of twelve months to evaluate the residual efficacy of the sprayed products. Furthermore, the L1014F-kdr target-site mutation and the L119F-GSTe2 mediated metabolic resistance to pyrethroids were genotyped on a subset of mosquitoes from the EHT to assess the potential cross-resistance. All Anopheles species tested were fully susceptible to clothianidin and clothianidin + deltamethrin mixture in CDC bottle assay while resistance was noted to deltamethrin. Accordingly, Fludora® Fusion (62.83% vs 42.42%) and clothianidin (64.42% vs 42.42%) induced significantly higher mortality rates in EHT than deltamethrin (42.42%) against free flying An. funestus from Elende in month 1 (M1) and no significant difference in mortality was observed between the first (M1) and sixth (M6) months of the evaluation (P > 0.05). However, lower mortality rates were recorded against An. gambiae s.s from Nkolondom (mortality rates 50%, 45.56% and 26.68%). In-situ cone test on the wall showed a high residual efficacy of Fludora® Fusion and clothianidin on the susceptible strain KISUMU (> 12 months) and moderately on the highly pyrethroid-resistant An. gambiae strain from Nkolondom (6 months). Interestingly, no association was observed between the L119F-GSTe2 mutation and the ability of mosquitoes to survive exposure to Fludora® Fusion, whereas a trend was observed with the L1014F-kdr mutation. This study highlights that Fludora® Fusion, through its clothianidin component, has good potential of controlling pyrethroid-resistant mosquitoes with prolonged residual efficacy. This could be therefore an appropriate tool for vector control in several malaria endemic regions.

Pheromone traps and climate variations influence populations of Sahlbergella singularis (Hemiptera: Miridae) and associated damage of cocoa in Cameroon.

Knowledge of insect pest ecology and biology is important for maximizing crop protection and reducing crop losses. Currently, we lack an efficient control program for the cocoa mirid Sahlbergella singularis Haglund (Hemiptera: Miridae), the principal insect pest of cocoa in West and Central Africa. A 2-yr study was conducted in 11 plantations across Ayos and Konye, two of the largest cocoa growing areas of Cameroon. We evaluated the effects of mirid sex pheromone and climatic variations on mirid population dynamics and their associated cocoa damage. Sex pheromone traps caught 1.5-fold higher mirids in Ayos than in Konye, with more overall counts in 2015 than in 2016. Cocoa pod counts were also significantly higher in 2015 than in 2016 and were negatively correlated with temperature and relative humidity. In both localities, mirid populations and associated cocoa pod damage were suppressed in plantations where sex pheromone traps were used. Damage incidence was positively correlated with mirid counts, confirming that the cocoa pod is the preferential site for mirid feeding and reproduction. As such, damage incidence could be used as proxy for comparative mirid population level due to the mirid's cryptic habit. Of the recorded weather variables, only relative humidity was correlated (negatively) with damage severity. Our data on the relationships between damage caused by mirids and their population dynamics and sex pheromone trap catches suggest that an effective control strategy using mass trapping could be developed for mirid management in cocoa plantations.

Field evaluation of synthetic sex pheromone traps for the cocoa mirid Sahlbergella singularis (Hemiptera: Miridae).

BACKGROUND: Field trapping experiments were conducted to evaluate the attractiveness of five different pheromone blends as well as the impact of trap design on attractiveness towards cocoa mirids, Sahlbergella singularis Hagl. and Distantiella theobroma (Dist.), in Cameroon. RESULTS: A total of 361 adults of S. singularis (359 males and two females) were caught. The highest numbers of mirids were found in traps with pheromone blends that combined a monoester and a diester, compared with traps with the diester or the monoester individually and control traps with no pheromone. Rectangular traps caught significantly more mirids compared with delta traps. The mean number of 5.1 mirids trap⁻¹ year⁻¹ caught in rectangular traps was significantly higher compared with the 1.8 mirids trap⁻¹ year⁻¹ for the delta traps. CONCLUSION: The data revealed that rectangular traps containing pheromone blends combining both the monoester and the diester have a good potential to lure and trap adult males of S. singularis on cocoa farms. The pheromone blends used were specific for S. singularis, and the use of pheromone traps appears to be a promising strategy for incorporation into integrated pest management strategies for the monitoring or even the control of S. singularis in cocoa plantations.