| Sitobion avenae is one of the most serious insects to damage the wheat in China and overseas.Chrysoperla sinica is the important natured enemy for consuming various pests and being voracious,so that it has potential ability to control the number of the wheat aphids. Pest is poikilotherm, so temperatures as a key abiotic external factor on insect development have been studied extensively. We incorporated the life table and the predation rate to understand the control capability, aiming to show the efficient biological control of C. sinica for S. avenae.1. Sitobion avenae life table at different temperaturesThe age-stage life tables of S. avenae were assessed at 16℃, 19℃, 22℃, 25℃ and 28℃ in the laboratory. The fecundity, net reproduction rate, adult duration and the longevity of S. avenae were first increased and then decreased with the temperature increasing, and the maximum values appeared,16.7±2.0 nymphs, 14.11±1.90 nymphs, 15.6±1.6 d, 26.4±1.5 d, respectively at 22 ℃. The developmental duration of the nymphs and the mean generation time reduced with the temperatures increasing, and the shortest ones were found out at 25℃, 12.83±0.30 d. Meanwhile, the intrinsic rate and finite rate of increase were increased at higher temperature, and the maximum were found at 25℃,0.20±0.01 d-1, 1.22±0.01 d-1. However, at 28℃, the intrinsic rate of increase was negative,-0.14±0.02d-1, and the finite rate of increase, net reproduction rate, fecundity and longevity appeared the minimum values at the same time compared with other tested temperatures, 0.87±0.02 d-1, 0.16±0.04 nymphs, 0.4±0.1 nymphs, 15.5±0.3 d, respectively. These results indicated that S. avenae could develop normally at 19℃ and 22℃, but the aphid did not perform well at 28 ℃.2. The two sex, age-stage life table and predation rate of C. sinicaThe life history and predation rate of C. sinica were studied at 22℃. According to the age-stage,two-sex life table, the development duration of larval was about 10 d. The 2nd instar had the shortest duration, but the predation rate(43.31±2.77 aphids/individual) was higher than that of the 1st instar(26.81±0.87 aphids/individual). Both the predation rate and even the sum were far less than that of the 3rd instar(185.92±8.58 aphids/individual). The predation rates between the female(261.18±14.14 aphids/individual) and the male(251.93±11.89 aphids/individual) had no significant difference. The intrinsic rate and finite rate were 0.10±0.01 d-1, 1.10±.008 d-1. The fecundity and net reproduction rate were 310.36±44.54 eggs, 131.31±35.45 eggs/individual. The mean generation time was 48.99±1.64 d. Meanwhile, the mean predation rate was 254.81±8.70, and the transformation rate was 1.94±0.74, and the stable predation rate and the finite predation rate were7.57±0.17 and 8.37±0.19, respectively.The predation rates of C. sinica fed on S. avenae were compared at 16℃, 19℃, 22℃, 25℃ and28 ℃. Every treatment has the high survival rate, and predation rate almost is similar to the net predation rate. With the growth of the stage, the predation rate increased, and the 3rd larval consume aphids more than both the 1st and 2nd instar at the same temperature. However, with the temperature increasing, the development period shorten, and the 1st and 2nd predation rate vary, so that the most consuming of first instar larval was 39.08±2.08 aphids/individual at 19℃, but the second one was52.75±4.18 aphids/individual at 25℃. Predation rate of the 3rd larva decreased with the temperature increasing and the largest one is at 19 ℃, 218.40±12.46 aphids/individual, and the lowest showed at 28 ℃, 115.95±6.07 aphids/individual. Moreover, all the predation rates at different temperatures had no significant difference. |
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