چكيده انگليسي :
Tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most important pests of tomatoes. This pest attacks all plant growth stages and causes severe damage. Heat shock and experiencing high temperatures in a short period of time can lead to the lethal and sublethal effects on the insect pests. In this study, the effects of heat shock were investigated on adult survival, fertility life table parameters, susceptibility to insecticides, and activities of the stress‐response and detoxification enzymes in tomato leaf miner moth. To assess the heat shock effects, different life stages of the pest were subjected to temperatures of 36, 39, and 42° C for one hour and then returned to 25° C. Based on the results, the highest length of the pre-pupa time was observed in insects treated with heat shock at 39 and 42 ° C, which was significantly higher than that of control and heat treatments at 36 °C. The highest intrinsic rate of natural increase (rm), finite rate of increase (λ), gross reproduction rate (GRR), and fertility were observed in treated insects at 36 ° C. These parameters were 0.1444 (female/female/day), 1.155 female/female/day, 198.06 eggs, 259.38 egg/per female, respectively. The shortest time of the pre-oviposition period of adult and pre-oviposition period was observed in heat treatment of 36 ° C. The difference between the numbers of oviposition days was significant in different treatments. The highest number of oviposition days was observed in heat shock treatments of 25 and 36 °C. The number of oviposition days significantly decreased with the increasing temperature of heat treatment and reached to 12.35 days at 42 °C. The age-specific life expectancy (ex) of the T. absoluta decreased with increasing temperature of heat treatment. Heat shock also had a significant effect on the lifespan and fertility of newly emerged adults. After heat shock, the highest lifespan, number of eggs, number of oviposition days were observed at 36 ° C and the lowest at 42 ° C. The results showed that heat shock can significantly reduce the percentage of egg hatching in T. absoluta. The development time of eggs, larvae, pre-pupae, pupae, and adult insects were not affected and no significant difference was found between treatments. To investigate the effect of heat shock on the susceptibility to insecticides, the mean lethal concentrations (LC50) were determined using fourth instar larvae (L4) subjected to the temperature of 42°C. The bioassays were conducted using a leaf dip method. The amount of LC50 values of thiacloprid, spinosad and Bt increased from 2248, 21.7 mg a.i/L and 1.408×106 spores in the control treatment to 2867, 77.8 mg a.i/L and 3.68×106 spores in treated insects, respectively. It indicates a decrease in the sensitivity of T. absoluta larvae to the tested insecticides after heat shock exposure. The effect of heat shock on the activity of the stress‐response enzyme (catalase) and detoxification enzymes (esterases, glutathione S-transferases, and cytochrome P450 monooxygenases) were also investigated using second instar larvae. The results showed a significant effect of heat shock on the activity of esterases 2 hours after treatment of 25 and 42 ° C. However, heat shock did not induce a significant effect on activity of glutathione S-transferases, catalase, and cytochrome P450s. Six hours after heat shock, the activity of esterases, catalase, and cytochrome P450s increased, increased, and decreased, respectively. However, there was no significant difference in the activity of glutathione S-transferases. The contents of lipids, glucose, and glycogen were not significantly different from that of control at 6 and 12 hours after treatment of 42 °C. However, 24 hours after heat shock, the lipid and glucose contents were decreased, but no difference was observed in the glycogen content.
