[Biological and environmental study of Thrips tabaci(lindeman) Thysanoptera:Thripidae and Evaluate Varieties to Infection]

The study was conducted in onion field in Nashabia ( Damascus Countryside) to study the population dynamics of onion thrips,and to study the effects of deferent temperatures (20-25-30 °C) on some biological character of onion thrips Thrips tabaci Lindeman (Thripidae: Thysanoptera). The egg hatching occurred in 9.1±93.1 days in 20 °C, 7.4± 0.69 days in 25 °C and 2.24± 0.3 days in 30 °C. The first instars nymph development was completed in about 7.97 ±93.1 days in 20°C, 3.95± 0.41days in 25°C and 1.95± 0.41in 30 °C. The second instars nymph development was completed in about 6.68 ±1.02 days in 20°C, 4.72±0.75 days in 25°C and 2.15±0.54 in 30 °C. The prepupa development was completed in about 7.7±1.70 days in 20°C, 4.2 ±6310 days in 25°C and 1.83 ±630 in 30 °C. The pupa development was completed in about 4.9± 0.95days in 20°C, 2.88 ±63..days in 25°C and 1.86± 0.32days in 30 °C. The generation development ( on egg to adult emigration) was completed in about 36.39 ±930. days in 20°C, 20.52 ±630. days in 25°C and 10.02 ±9301 days in 30 °C. The result showed that Development threshold Ø for egg is 17.4 °C and the Thermal contestant (k) is 29.49 degree/day. The Development threshold for first instars nymph is 17.47 C and the Thermal contestant (k) is 25.46 degree/day. The Development threshold for second instars nymph is 16.56°C and the Thermal contestant (k) is 31.25 degree/day . The Development threshold for prepupa is 17.93°C and the Thermal contestant (k) is 32.8degree/day. The Development threshold for pupa is 14.19°C and the Thermal contestant (k) is 30.30 degree/day. The Development threshold for on generation ( on egg to adult emigration) is 18.33°C and the Thermal contestant (k) is 125 degree/day. Results indicate that the adult thrips started colonizing the crop 1n 10/3 until 14/6/2009 on two methods. The peak population of adult thrips was in 13/5 with 8352 adult/45 plant on Accumulate method and 3298 adult/ 45 plant on wag method. The number of adult thrips was differ on month to month during this study, The peak population of adult thrips recorded in May in two methods. The egg laying started 1n 9/4 with 383 eggs to 14/6 with 17 eggs, the peak population of eggs was in 13/5 ( 8522/45 plant) The appear of first instars nymph was in 17/3 to 2/6/2009. The peak population of first instars nymph was in 5/5 ( 5022/ 45 plants) on and in 13/5 on wag method ( 2121/ 45 plants). The appear of second instars nymph was in 9/4 to 24/5/2009. The peak population of second instars nymph was in 13/5 ( 5778/45 plants) on Accumulate method and in 24/5( 1677/45 plants) on wag method. There was differ on number of different stages of onion thrips on upper leaf surface and on lower leaf surface. The number of different stages of onion thrips on upper leaf surface was 23324 adult thrips, 7431 eggs, 10605 first instars nymph and 17710 second instars nymph, when the number of different stages of onion thrips on lower leaf surface was 4125 adult thrips, 18761 eggs, 3173 first instars nymph and 3323 second instars nymph. The mortality rate was differ on month to other and on two leaf surface, The peak mortality rate of adult thrips 46.7% was in June, and the lesser mortality rate was in Marsh 11.3%,the rate mortality of adult thrip was higher on lower leaf surface 22.1% than on upper leaf surface 16.4%. The peak mortality rate of first instars nymph 13% was in May, and the lesser 6% was in April, the rate mortality of first instars nymph was 11.7% on upper leaf surface, and 11.8% on lower leaf surface. The peak mortality rate of second instars nymph 82% was in June, and the lesser 14.9% was in April, the rate mortality of second instars nymph was15.7% on upper leaf surface, and 21.5% on lower leaf surface.