Background: In greenhouse tomato systems, Bemisia tabaci is a major pest. Understanding its bioecology is crucial to improve biological control, especially using parasitoids. This study focused on optimizing such strategies under protected cultivation. The research was conducted in the northeastern Algerian Sahara during the 2023-2024 growing season. 
 
Methods: This study investigated whitefly bioecology and the effectiveness of the parasitoid Encarsia formosa in greenhouse tomato (var. &lsquo;Tofan&rsquo;). Integrated control strategies, including insect-proof nets, were evaluated. Five parasitoid releases were conducted based on pest developmental stages. The response of four tomato varieties (Tofan, Tavira, Sahra and Zahra) to whitefly infestation was also assessed. 
 
Result: Parasitism rate peaked during the third and fourth developmental stages of B. tabaci. Pest populations declined significantly, reaching a parasitism rate of 76.6%. Considering the mean larval infestation level of the whitefly, which is evaluated of 15.01 larvae.plant-1, the corresponding average parasitism rate reached 11.50 parasitoids.plant-1. Parasitism rate showed a significant positive correlation with temperature. No significant relationship was found between parasitism and ambient humidity. However, adult whitefly abundance was positively correlated with relative humidity. Among the four tomato varieties, &lsquo;Tofan&rsquo; had the lowest infestation (5.42&plusmn;0.21 insects.plant-1), while &lsquo;Zahra&rsquo; showed the highest adult density (11.00&plusmn;0.42 insects.plant-1). 
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Population Dynamics and Biological Control of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) on Greenhouse Tomatoes in the Northern Algerian Sahara