نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه گیاهپزشکی، دانشکده کشاورزی، دانشگاه ارومیه، ارومیه، ایران
2 مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان آذربایجان غربی، سازمان تحقیقات آموزش و ترویج کشاورزی، ارومیه، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Greenhouse whitefly, Trialeurodes vaporariorum, Westwood (Hemiptera: Aleyrodidae) is one of the most serious pests of many horticultural and greenhouse crops that causes quantitative and qualitative damages in the yield of greenhouse products. However, various controlling methods (e.g., agronomic, mechanical, behavioral, and biological) are used for management of greenhouse whitefly pest, but usage of synthetic insecticides is the only easy and cost-effective strategy for dealing with arthropod pests in many crop production systems, which is more common controlling method in Iran. Due to the extensive usage of non-selective insecticides against T. vaporariorum, and their side effects on natural enemies, we used in the present study, selective, harmless, and eco-friendly insecticides. In this research, we evaluated the lethal and sublethal efficiency of two insecticides, thiocyclam hydrogen oxalate and spiromsifen. Thiocyclam hydrogen oxalate is a broad-spectrum systemic as well as a contact insecticide. It is highly effective against a wide range of insect pests, particularly sucking mouth parts (e. g., aphids, leafhoppers, and whiteflies). Spiromesifen, is known as a non-systemic insecticide which belongs to the spirocyclic pheny substituted tetronic acid class. It is effective against a broad spectrum of pests and it disrupts the biosynthesis of lipids including triglycerides and free fatty acids. Sublethal effects of thiocyclam hydrogen oxalate and spiromsifen were studied by considering the biological properties and life table parameters of T. vaporariorum. Our results may improve T. vaporariorum control efficiency in greenhouses meanwhile using reduced concentrations of these insecticides, which may be resulted in hindered host resistance to aforementioned insecticides and reduced their residuals on greenhouse crops.
Materials and Methods
The colony of greenhouse whitefly was collected on ornamental crops (vervain and hollyhocks) at the greenhouse in Department of Horticulture at Urmia University during September 2023. The gathered whitefly population was reared on bean (var. MINA) in plastic pots (15 × 19 cm) under controlled greenhouse conditions (27 ± 2°C, 65% ± 5% RH, and a photoperiod of 16: 8 L: D h).
The dipping method was used for bioassay and life table studies against third instar nymphs of T. vaporariorum. The LC50 value of thiocyclam hydrogen oxalate and spiromsifen insecticides for third instar nymphs of the whitefly were obyained 392.627 and 854.871 ppm, respectively after 24 hours. The obtained LC25 concentrations (117.520 and 731.548 ppm), were used to estimate the sub-lethal effects of thiocyclam hydrogen oxalate and spiromsifen on the biological parameters of third instar nymphs of the greenhouse whitefly, respectively. To study the sublethal effects of both used insecticides, 50 same-aged of the third instar nymphs of the greenhouse whitefly were selected from the insect colony and then dipped in above mentioned sublethal concentrations of insecticides. The treated nymphs were transferred into petri dishes until the adults were appear. After adult emergence, their eggs were used to life table studies. The age stage, two-sex life table method was used to analyze the collected data. We used the bootstrap technique with 100,000 iterations to estimate the variance and standard errors of the biological and population parameters and Sigma Plot software used to draw graphs. The growth of the pest population over 60 days was done with Timing-MsChart software.
Results
The present study demonstrated that thiocyclam hydrogen oxalate insecticide showed more acute toxicity on third instar nymphs of the greenhouse whitefly. Moreover, exposure of third instar nymphs to sublethal concentrations (LC25) negatively affected the development, survival, and reproductive characteristics and demographic factors. According to our findings, sublethal concentration of examined insecticides showed a significant increase in pre-adult duration of the pest on thiocyclam hydrogen oxalate treatment compared to spiromesifen and control treatments. The female adult’s lifespan/longevity was affected due to the usage of sublethal concentration of mentioned insecticides. The lowest duration of adult pre-reproductive period (APRP) in control treatment was recorded as 1.33 days, while this parameter increased in treatments. Fecundity was reduced significantly in sublethal concentration of the insecticides compared to the control. The highest value of fecundity in control treatment was recorded 11.85 eggs per female and the lowest value in thiocyclam hydrogen oxalate was obtained (1.7 eggs per female). The mean oviposition period of greenhouse whitefly decreased from 4.44 days in control to 1.4 and 1.38 days in thiocyclam hydrogen oxalate and spiromsifen, respectively. All population gowth parameters (R0, r and λ) of T. vaporariorum treated with sublethal concentration of the used insecticides were significantly affected compared to the control. The sublethal concentration of thiocyclam hydrogen oxalate and spiromsifen reduced the net reproductive rate (R0) from 4.21 eggs per female in each generation in the control treatment to 0.29 and 0.54 egg in thiocyclam hydrogen oxalate and spiromsifen, respectively. The intrinsic rate of increase (r) in thiocyclam hydrogen oxalate, spiromsifen and control were recorded 0.0176, 0.0271, .0525 day-1, respectively. Other parameters, such as finite rate of increase (λ) and gross reproductive rate (GRR), in spiromesifen and thiocyclam hydrogen oxalate treatments were also significantly lower than the control treatment. The mean generation time (T) of the greenhouse whitefly affected by the LC25 concentration of spiromesifen compared to the control treatment.
Conclusions
The overall results demonstrated that both of the used insecticides could be considered as effective insecticides in management of T. vaporariorum.
کلیدواژه‌ها [English]
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