Document Type : Research Article
Authors
1
Depatment of plant protection, Faculty of agriculture, Urmia university, Urmia, Iran
2
Department of Plant Protection, Faculty of Agriculture, Urmia University, Urmia, Iran
3
Natural resources research center, Agriculture research, Education and Extension organization (AREEO), Urmia, Iran
10.22067/jpp.2026.100786.1294
Abstract
The greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), is a globally significant pest of protected crops, infesting over 850 plant species. It causes direct damage through phloem sap feeding and indirect damage by excreting honeydew that promotes sooty mold growth, reducing both photosynthetic capacity and marketable yield. Furthermore, it vectors numerous plant viruses, exacerbating economic losses. Historically, chemical control has been the primary management strategy; however, the intensive and repeated application of synthetic insecticides have led to widespread resistance, environmental contamination, non-target effects on natural enemies, and human health concerns. These challenges necessitate the evaluation of newer, selective insecticides with novel modes of action and reduced ecological footprints. Emamectin benzoate, an avermectin derivative, acts as a chloride channel activator causing rapid neuromuscular paralysis, while acetamiprid, a neonicotinoid, disrupts synaptic transmission via nicotinic acetylcholine receptor antagonism. Their combined formulation offers potential synergistic effects and resistance-delaying benefits. In contrast, alpha-cypermethrin, a Type II pyrethroid, disrupts voltage-gated sodium channels, providing fast knockdown but raising concerns about non-target toxicity and resistance. Sublethal effects are critical for predicting long-term population dynamics, as pests in agricultural systems frequently encounter degrading pesticide residues. This study aimed to comprehensively evaluate the lethal (LC₅₀) and sublethal (LC₂₅) effects of emamectin benzoate- acetamiprid and alpha-cypermethrin on the age-stage, two-sex life table parameters and population projection of T. vaporariorum under controlled laboratory conditions.
Materials and Methods: A laboratory colony of T. vaporariorum was established from adults collected from an untreated greenhouse at Urmia University, Iran, and maintained on potted tomato plants (cv. 'Firmont') for three generations to ensure uniformity. All experiments were conducted at 25 ± 2°C, 65 ± 5% relative humidity, and a 16:8 h (L:D) photoperiod. Leaf-dipping bioassays were performed on third-instar nymphs using five logarithmic concentrations of each insecticide—emamectin benzoate 4.8% + acetamiprid 6.4% (EC 11.2%) and alpha-cypermethrin 10% SC—alongside a distilled water control. Treated leaves were air-dried and maintained in Petri dishes with moistened cotton. Mortality was recorded 24 hours post-treatment, and LC₅₀ and LC₂₅ values were estimated by Probit analysis using SPSS software, with four replicates per concentration (15 nymphs each treatment). For sublethal effect assessment, third-instar nymphs were exposed to the LC₂₅ concentrations of each insecticide. Surviving adults were transferred to clean plants for oviposition, and 50 synchronized eggs were selected as the initial cohort for life table studies. Each neonate was individually reared in plastic containers with insecticide-free tomato leaves, replaced every 3–4 days. Daily observations recorded developmental duration, stage-specific survival, adult longevity, pre-oviposition period (APOP), total pre-oviposition period (TPOP), oviposition period, and daily fecundity until the death of all individuals. Life table data were analyzed using the age-stage, two-sex life table theory with TWOSEX-MSChart software. Population parameters—net reproductive rate (R₀), intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T)—were calculated, with means and standard errors estimated via the bootstrap method (100,000 iterations) and compared using the paired bootstrap test. Population projections over 60 days were performed using TIMING-MSChart.
Results: Alpha-cypermethrin exhibited higher acute toxicity (LC₅₀ = 8.601 ppm) compared to emamectin benzoate + acetamiprid (LC₅₀ = 10.472 ppm). However, sublethal exposure to both insecticides significantly prolonged pre-adult developmental duration, reduced adult longevity, and decreased fecundity compared to the control. The lowest and highest fecundity rated was observed in emamectin benzoate + acetamiprid treatment (3.62 eggs/female) and control treatment (7.79 eggs/female), respectively. Key population parameters including the net reproductive rate (R₀), intrinsic rate of increase (r), and finite rate of increase (λ) were significantly reduced in both treatments, with the most pronounced decline recorded in the emamectin benzoate + acetamiprid treatment (R₀: 0.52 vs. 4.009 offspring/individual; r: -0.0184 vs. 0.0416 day⁻¹) compared to the control group . Mean generation time (T) was significantly extended in insecticide-treated groups. Population projection over 60 days confirmed slower population growth in both treatments, particularly with the combined formulation. Although alpha-cypermethrin showed greater acute toxicity, the emamectin benzoate + acetamiprid combination exerted deeper and more persistent sublethal effects, resulting in a substantial reduction in population growth potential compared to control. Its dual mode of action and lower resistance risk make it a more suitable candidate for integrated pest management (IPM) programs against greenhouse whitefly. However, further studies on its compatibility with natural enemies are recommended before field implementation.
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