Mohamed El Aalaoui ¹ Said Rammali ² Fatima Zahra Kamal ² Radu Lefter ³ Gabriela Calin (Mihalache) ^4* Vasile Burlui ⁴ Ciobica Alin ⁵ Petroaie Dacia antoneta ⁶ Otilia Novac ⁶ Bogdan Novac ⁶ Mohamed Sbaghi ¹

• ¹ National Institute for Agricultural Research (Morocco), Rabat, Morocco
• ² Hassan Premier University, Settat, Beni Mellal-Khenifra, Morocco
• ³ Romanian Academy, Bucharest, Romania
• ⁴ Apollonia University, Iași, Romania
• ⁵ Alexandru Ioan Cuza University, Iași, Romania
• ⁶ Grigore T. Popa University of Medicine and Pharmacy, Iași, Iasi, Romania

Phenacoccus solenopsis Tinsley, poses a significant threat to a range of crops worldwide. This study aimed to evaluate the efficacy of entomopathogenic fungi (Alternaria murispora and Alternaria destruens) and bacteria (Streptomyces bellus-E23-2) against adult females of P. solenopsis under laboratory (26±2 °C) and greenhouse conditions. Laboratory trials tested A. murispora, A. destruens (10⁴-10¹⁰ conidia mL⁻¹), and S. bellus E23-2 (10⁴-10¹⁰ cfu mL⁻¹), alone and in combination, recording mortality rates and LC50 values. Greenhouse trials tested the best lab treatments on infested potato plants, monitoring pest density and plant quality. In laboratory trials, A. murispora at 10 10 conidia mL⁻¹ was the most effective, achieved 79.7% mortality (LC50= 1.338×10 8 conidia mL⁻¹ after 14 days). Combination treatments significantly enhanced efficacy, with A. murispora + S. bellus E23-2 (10 10 conidia mL⁻¹ + 10 10 cfu mL⁻¹) reaching 85.3% mortality. In greenhouse trials, the combination treatments notably reduced P. solenopsis densities and increased the number of infected mealybugs, with A. murispora + S. bellus E23-2 being the most effective. These treatments did not harm plant quality, unlike imidacloprid, which reduced visual quality despite its high efficacy. Alternaria murispora and S. bellus E23-2 effectively control P. solenopsis, providing a sustainable, plant-safe alternative to chemical insecticides.