Document Type : Research Article
Authors
1
Department of Plant Protection, Faculty of Agriculture, Urmia University, Urmia, Iran.
2
Department of Plant Protection, Faculty of Agriculture, Urmia University, Urmia, Iran
3
Plant Protection Research Department, West Azarbaijan Agricultural and Natural Resources Research Center, Agricultural Research, Education and Extension Organization (AREEO), Urmia, Iran
Abstract
Introduction[1]
The tomato leafminer moth, Tuta absoluta, (Meyrick), is one of the most important pests in green houses and tomato-growing regions in Iran and the world, which resulting in up to 100% yield losses during serious outbreaks. The tomato leafminer moth is known as an oligophagous pest damaging solanaceous crops, including eggplant, pepper, potato, and sweet pepper, tobacco, as well as solanaceous weeds. It causes quantitative and qualitative damages in the yield of greenhouse products. In direct damage, all parts of host plants are damaged by larvae, and indirect damage occure through wounds that prepare the entrance of pathogens. In the other hands, some biological properties (leaf mining habit, short life span and high reproductive rates) of the tomato leafminer moth resulted in development to insecticide resistance. In the present study, we used selective, harmless, and eco-friendly insecticides to study the lethal and sublethal (LC25) effects of two insecticides, Indomect®and Imunit® through the life table parameters and population projection of T. absoluta under laboratory conditions. Indomect is known as a non-systemic insecticide that is a combination of two insecticides, indoxacarb and emamectin benzoate. This disrupts the nervous system and kills target insects by keeping the chlorine channel open. Additionally, its contact effect is short and causes the death of target pest through digestion and nerves. Imunit® is combination of Teflubenzuron and Alphacypermethrin (Teflubenzuron 75 G/L + Alphacypermethrin 75 G/L SC). Teflubenzuron is classified under IRAC - Group 15, which controls insects by inhibiting the formation and growth of the cuticle (exoskeleton). Alphacypermethrin is classified under IRAC - Group 3, which controls insects by contact and ingestion of applied residues. Our results may increase to T. absoluta control efficiency in greenhouses through using reduced concentration rates of the studied insecticides, which in turn may be led to delay in pest resistance and reduction of their residuals on greenhouse crops.
Materials and Methods
The colony of the tomato leafminer moth, was collected on tomato crops at the greenhouse in Department of Plant Protection at Urmia University. The gathered T. absoluta population was released into cages (90×60×50 cm on tomato (var. Vania) pots under controlled greenhouse conditions (25 ± 2°C, 70% ± 5% RH, and a photoperiod of 16: 8 L: D h). To obtain dose-mortality response for adult stage of greenhouse whitefly, we followed the bioassay methods described by Ebneabbasi et al. (2023). The leaf dipping method was used in bioassays. For this purpose, the tomato leaf containing three days old of T. absoluta (15 eggs) was dipped in five different concentrations (in the ranges of 83–750 ppm) for each insecticide for 20 s. The treated leaves were air-dried for 20 min at room temperature, then put into the ventilated plastic containers (4cm in height and 2 cm in diameter) containing the treated leaflet. Distilled water was used as a control. Four replicates were set up for each of the insecticides and controls. Percentage adult’s mortality was counted 24 h after treatment. To prevent the desiccation of the leaves, the basal ends of the tomato leaflets were wrapped in moistened cotton wicks. The lethal (LC50) and sublethal (LC25) concentrations, and 95% confidence limits
in each treatment were obtained using the Probit analysis (Finney, 1971), which conducted by SPSS software (Ver. 20, 2011). To study the sublethal effects (LC25) of both used insecticides, 53, 49, 59 same-aged of the eggs were selected from the insect colony and then dipped in above mentioned sublethal concentrations of insecticides. The treated eggs were transferred into plastic containers until the first instar larvae of T. absoluta were appear, then they 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 and Discussion
The results showed that, Imunit® (LC50: 239.412 ppm) was more toxic than Indomect® (LC50: 247.541 ppm) on the T. absoluta eggs. The sublethal concentration (LC25) of Imonit insecticides affected life table parameters of T. absoluta significantly compared with control, and it prolonged the incubation period of eggs (3.04±0.03 d), pupal (6.33±0.11 d) and total pre-adult developmental time (20.67±0.25 d) of the tomato leaf miner moth, significantly more than control treatment. Although, there was no significant difference in terms of population growth parameters (intrinsic rate of increase, finite population growth and net reproductive rate) between the used insecticides. The rate of these parameters was decreased in insects whose parents were treated with sublethal concentrations of aforementined insecticides compared to the control. The results also demonstrated that population growth of the leaf miner moth in different treatments was exactly in consistent with the estimated population growth parameters. For example, moths treated with the used insecticides, had slower growth rate and, thereby prolonged mean generation time (T).
Concusion
The overall results of this study showed that both of the insecticides can be used alternately as an integrated management program for tomato leaf miner moth.
Keywords
Subjects
