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The toxicity of cypermethrin at 0.02 μg L^-1 concentration in relation to salinity (0 and 14 ppt) and temperature (16±1 and 25 ± 1°C) was studied on the liver tissue of zebra fish (Aphanius sophiae) exposed to cypermethrin for 14 days under labratory condition. The liver tissue changed significantly with changes in salinity and temperature. The major changes were overlapped hepatocytes, nucleous irregularity, cloudy swelling, atrophy, fat degeneration, pyknosis, focal necrosis, karyolysis, accumulation of kupffer cell, necrosis and bile stagnation. The results showed that sensitivity to cypermethrin increased with decrease in salinity and increase in temperature.This fish is, therefore, not a suitable indicator for cypermethrin assessment in aquatic ecosystems, and if considered as an indicator, the temperature and salinity should also be considered.

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Tomato leaf miner, Tuta absoluta (Meyrick), is a serious pest of the greenhouse in Iran. Chemical control is the main method in high infestation conditions to deal with this pest. In this study, the efficacy of five insecticides from different groups consisting of abamectin, spinosad, imidacloprid, indoxacarb and cypermethrin was examined on the egg, larvae and adult stages of T. absoluta in laboratory conditions. The LC50 values of the insecticides were estimated at the larval stage. The results showed that abamectin had the most and imidacloprid had the least ovicidal effect. None of the tested insecticides had a satisfactory effect on the adult stage. The maximum adulticide impact was 40% for spinosad. Abamectin with 0.45 mg ai.l-1 of LC50 value had the most toxicity and imidacloprid with 980 mg ai.l-1 of LC50 value had the least toxicity on the third instar larvae. According to the findings, abamectin and spinosad had the highest toxicity against three developmental stages (egg, larvae and adults) of the pest and can be used in infested tomato fields, when all life stages of T. absoluta are present at the same time. Meanwhile, it is recommended to use selective insecticides such as indoxacarb, when natural enemies are very active or the population of the tomato leaf miner is mostly at the larval stage.

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Several phytophagous insect pests are known to attack okra, Abelmoschus esculentus (L.) Moench in the field. However, information on the fruit-damaging species and the effective time for insecticide application(s) is still scanty. Field experiments were conducted in 2017 and 2018 to identify the categories of damage inflicted on okra fruits by associated insect herbivores and to ascertain the phenological growth stage in which insecticide applications will significantly reduce insect-induced fruit damage and improve crop yield. Treatments consisted of the application of Cypermethrin 20EC at two-week intervals on NHAe47-4 variety of okra during the vegetative stage (VGS), reproductive stage (RGS), VGS + RGS, and no spray (control). The setup was in randomized complete blocks with four replicates. Results showed that incisions, feeding lesions, localized discolorations, bumps, distortions, and larval exit holes are the major fruit damage symptoms caused by field insect pests of okra. Generally, fruit damage was significantly reduced, while fruit yield was higher in plots that received insecticide sprays at vegetative and reproductive stages than in the control. Fruit production increased significantly by 56.9–69.6% and 57.7–73.1% in 2017 and 2018 in treated plots compared to control, respectively. Fruit damage was reduced by 37.5-92.5% (2017) and 44.6–94.6% (2018), and fresh fruit yield of okra was increased by [58.8–75.0% (2017) and 63.1-76.1% (2018)]. We conclude that an effective field management strategy for insects associated with okra fruit damage should include potent control tactics at the crop's vegetative and reproductive growth stages.

 

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The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae) is one of the important ornamental plant pests in urban regions. In this study, the microemulsion system was developed using cypermethrin insecticide as the active ingredient, xylene as the solvent, and surfactants including Tensiofix 8427 + SDS, and Tensiofix 8427 + SLS, and 1-butanol (cosurfactant), as stabilizer. The optimal microemulsion formulation was determined using a pseudo-ternary phase diagram using the water titration method. The microemulsions mean droplet sizes were in the range 11.2–22.8 nm. The droplets of all three formulations were spherical and uniformly dispersed in water. The mortality percentage was 66.66, 56.66, and 55.00% 24 h after aphids exposure to C_1-250 (cypermethrin: Tensiofix 8427 + SDS + 1-butanol: water, at the ratio of 10:20:70), C_2-250 (cypermethrin: Tensiofix 8427 + SLS + 1-butanol: water, at the ratio of 10:20:70), and C_3-250 (cypermethrin: Tensiofix 8427 + SLS + 1-butanol: water, at the ratio of 15:30:55), which increased to 92.86, 89.29, and 83.94%, 48 h after exposure, respectively. The results revealed that the microemulsion formulation containing cypermethrin 250 g/L was more effective in controlling A. gossypii than cypermethrin technical material and 150 g/L cypermethrin-based microemulsion.