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The development, survival, and reproduction of diamondback moth (DBM), Plutella xylostella (L.), were studied in laboratory at 25±1°C, 65±5% RH and a 14L: 10D hours photoperiodism on five host plants of: cauliflower (Brassica oleracea L. var. botrytis), two varieties of cabbage (B. oleracea L. var. capitata) namely ‘Globe Master’ and ‘Scarlet Ohara’, kohlrabi (B. oleracea L. var. gongylodes), and canola (B. napus L.). DBM larvae successfully survived on all host plants, although survival rate was lowest on canola (70.56%). The developmental time of immature stages ranged from 13.76±0.15 d on kohlrabi to 15.06±0.22 d on canola. The reproduction period and adult longevity were longest on cauliflower and common cabbage cultivar ‘Globe Master’ without any supplemental food while the highest fecundity of P. xylostella being also observed on these two host plants. The highest and lowest net reproductive rates were detected on cabbage cultivars, ‘Globe Master’ and 'Scarlet Ohara', respectively. Mean generation time was the longest on cabbage cultivar ‘Globe Master’. The respective descending order of intrinsic rates of population increase was on cauliflower, cabbage cultivar ‘Globe Master’, kohlrabi, cabbage cultivar ‘Scarlet Ohara’ and canola. Cauliflower and cabbage cultivar ‘Globe Master’ were recognized as the most suitable host plants for DBM.

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The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is an invasive pest of solanaceous crop plants, especially tomato, threatening worldwide tomato production. It has been a quarantine pest for Iran since 2010. However, it is now dispersed to all the main tomato production sites across the country. To assess crop loss and determine economic injury level (EIL), a field study was conducted in a 600 m² common research field for two consecutive years (2014-2015). Each tomato seedling (Super Strain B c.v.) was infested by different densities of the pest, including control, 1, 2, 4, and 8 tomato leafminer eggs in the first year and control, 2, 4, 8, and 16 leafminer eggs in the second year of study under cages. There was a significant relationship between the number of infested fruits and the number of leaf galleries made by tomato leafminer larvae. The EIL of tomato leafminer, according to the field experiments, was estimated to be 6.3 and 5.7 larvae/plant in 2014 and 2015, respectively. Evaluating the impact on crops and estimating the EIL are essential elements within a cost-efficient integrated pest management strategy, which provide practical tools for making informed decisions regarding the application of pesticides against T. absoluta.


 

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The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), is a serious pest of Poaceae plants, especially wheat and corn, in the world and in Iran. In this study, the demographic parameters of R. padi were determined at seven constant temperatures (8.5, 15, 20, 25, 27.5, 29 and 31±0.5 °C), 65±5% RH, and 14:10 (L: D) photoperiods on Zea mays L., KSC704 cultivar. The total lifespan, from birth to death, decreased with increasing the temperature from 8.5 to 29 °C, but the nymphal stage duration increased a little at 29 °C. The highest value of life expectancy (e_x) was observed at 8.5 °C and at 31 °C, the nymphs died before reaching the adult phase. The percentage of survival for nymphal stages was highest at 15 and 25 °C, and the net reproductive rate (R₀=23.671 female/generation) had the highest value at 15 °C. The intrinsic rate of increase (r_m) and the finite rates of increase (λ) increased at the temperature interval of 8.5 to 25 °C. At this range, the doubling time (DT) and the mean generation time (T) decreased as the temperature increased. According to the highest value of r_m (0.22 day^-1) and λ (1.134day^-1) and also the lower value of T (9.095 d) and DT (2.16 d), the temperature of 25 °C was determined as the optimal temperature and the data showed that the proper temperature range for growth and reproduction of this aphid was between 15-25 °C. The effect of temperature on reproduction, especially the intrinsic rate of increase (r_m), of R. padi would be useful for predicting its long-term population fluctuation over several generations and establishing integrated pest management (IPM) strategies against this pest.