<!-- *** Custom HTML *** --> The African mirid bug (Sahlbergella singularis) is the most economically important insect pest in cocoa farms. Pesticide management, although controversial due to the adverse effects of these substances on the environment and on human health, remains the main option used for controlling this pest. In the recent decades, the development of alternative approaches to synthetic pesticides is a requirement. Therefore, we used neem oil (NO) and ethanolic extracts (EE) from leaves at different concentrations to evaluate, in vitro, their insecticidal potentials against mirids. Mirid mortality increased significantly with increase in concentrations, values ranged from 32.5 to 92.5 % for EE and 52.5 to 97.5 % for NO. Apart from negative controls, Tween 80 and distilled water, that showed significant low mortality rates, both extracts revealed effectiveness comparable to the reference insecticide used in controlling mirids, except for EE by ingestion. Mirids treated by contact showed significantly high mortality rates (72.5 to 97.5 %) compared to those treated by ingestion (32.5 to 70.0 %). The greatest biological effectiveness values were obtained at a concentration of 8 % by contact exposure: 0.88 ml/ml (NO) and 0.73 g/ml (EE) for LC50 and ≈1 day to both extracts for LT₅₀. Given effectiveness comparable to that of the insecticide, both tested extracts should be considered as effective biopesticides for IPM against mirids, especially S. singularis.

The microbial biocontrol agents Beauveria bassiana (B. bassiana) and Metarhizium anisopliae (M. anisopliae) are highly effective in controlling various insect pests. However, their effectiveness often depends on biopesticide formulation, which could be affected by unfavourable environmental conditions. This study aimed to determine the compatibility of eight vegetable oils derived from raw palm, refined palm, sunflower, cotton, soybean, groundnut, neem, and canola in formulations of B. bassiana and M. anisopliae. This compatibility of oils with fungi was investigated by measuring fungal hyphal growth, conidial yield, fungal biomass, and conidial viability. The results showed a significant inhibition of B. bassiana growth in neem (2.08%) and raw palm oils (0.52%) and M. anisopliae in neem oil (0.28%). Conidia yield was high in the soybean (29.3 x 106 conidia/mL), groundnut (27.2 x 106 conidia/mL) and refined palm (23.83 x 106 conidia/mL) oils as well as vegetative growth for B. bassiana, while conidiogenesis of both fungal species was highest in soybean oil (29.3 x 106 conidia/mL and 44.4 x 106 conidia/mL for B. bassiana and M. anisopliae respectively). Fungal viability varied considerably, with the highest density of viable propagules obtained in Potato Dextrose Agar (PDA) culture media amended by sunflower oil for B. bassiana (43.2 x 104 viable propagules/ml) and in raw palm oil for M. anisopliae (97.4 x 104 viable propagules/ml). Taking these four parameters into account, it was concluded that the compatibility or toxicity of the oils to the two fungal species was mixed. The results of this study were relevant to the formulation of biopesticides based on effective strains of the two fungal species and constituted an essential component for this research program aimed at formulating biopesticides and testing their pathogenicity against insect pests under field conditions. Keywords: Vegetable oil, Cameroonian indigenous isolates, entomopathogens, compatibility, biopesticide.

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.