I.A. Saqr¹, A.K. Ali2 and S.B. Ghalia¹*
(1) Department of Plant Protection, Faculty of Agriculture, Latakia University, Latakia, Syria; (2) Higher Institute for Marine Research, Latakia University, Latakia, Syria.
*Email address of the corresponding author: [email protected]
The two-spotted spider mite, Tetranychus urticae Koch, is one of the most destructive agricultural pests worldwide due to its wide geographical distribution, broad host range, and rapid development of resistance to chemical pesticides. These challenges have increased the need for safer and more effective alternative control strategies, particularly plant-derived biocides. The aim of this study was to evaluate the efficacy of Melia azedarach oil and its nano-formulations prepared using silica nanoparticles and polyethylene glycol (PEG) against different life stages of T. urticae, mainly adult females and the first nymphal instar. Experiments were conducted using the treated paper disc dipping method with different concentrations of the essential oil (0.5, 1, 2, and 4%) and nano-formulations (100, 250, 500, 1000, 2000, and 3000 ppm). Mortality rates varied according to treatment type, concentration, life stage, and exposure duration. The base oil at 4% achieved mortality rates ranging from 21.33% to 72.29% in adult females and from 25.33% to 77.08% in the first nymphal instar over the experimental period. At 2% concentration, mortality reached 56.67% in adult females and 72.68% in nymphs. The nano-silica formulation at 2000 ppm showed increasing efficacy over time, with mortality rising from 32.00% to 81.90% in adult females and from 33.32 to 88.58% in nymphs. In contrast, the PEG-based formulation at the same concentration showed comparatively lower efficacy, with mortality rate ranging from 18.58% to 76.90% in females and 24.67% to 78.67% in nymphs. At 3000 ppm, nano-silica formulations achieved the highest and most rapid mortality response, reaching 85.99% mortality in adult females and 89.22% in nymphs, compared with 77.43% and 81.33% for PEG formulations, respectively. These results indicated that M. azedarach oil and its nano-formulations are promising candidates for inclusion in integrated pest management programs, although further field validation is still required.
Two-spotted spider mite, Tetranychus urticae, Melia azedarach oil, nano-silica, polyethylene glycol, PEG, integrated pest management.
https://doi.org/10.22268/AJPP-001541