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Evaluation of the Effect of Temperature on Biological Parameters of Two Spotted Spider Mite Tetranychus turkestani Ugarov & Nikoiski

The effect of six constant temperatures (15, 20, 25, 30, 35 and 40°c ) on biological parameters (immature develo) pmental time, females longevity, oviposition rate, preoviposition, oviposition, post-oviposition periods and the mean number of egg per female per day) and also demographic parameters (net reproductive rate, mean generation time , intrinsic rate of increase and finite rate of increase) of Tetranychus turkestani Ugarov & Nikolski were studied under laboratory controlled conditions: 55 ± 10 %RH and 16L:8D. The upper and lower thermal threshold were estimated 13.4 and 41.6 °C respectively. The highest and lowest juvenile development time were recorded 4.33 and 30.35 days at 35 and 15°C respectively. According to maximum intrinsic rate of increase (0.379), minimum mortality percent and also highest egg production per female (73.8) at 35°c , it can be concluded that this was the optimum temperature for population development of T. turkestani. Increase in mortality rate at 40ʹC indicates the proximity of the upper thermal threshold. No significant trend was found in daily fecundity rate between 6 temperatures. The total number of eggs laid per female were significantly different between the studied temperatures. The use of Logan et al. (1976) model allowed the description of temperatures influence the population growth. The values of Logan et al. model parameters, estimated by least-squares regression techniques, were p l = 0.102, p2 = 0.106 and p3 = 5.47. According to our results, the temperature ranges within which T. turkestani can develop, from 13.4°c to more than 40.00 is very broad. Althogether, this phytophagus mite has a high potential for population growth with regard to the temperature ranges and the high rates of increase were obtained from 0.089 to 0.379 between 15 and 35ʹtʹ. Further investigations concerning the influence of other biotic and abiotic factors on the biology of T. turkestani should be conducted to characterize the main factors responsible for changes in its population dynamics.