| Colaphellus bowringi Baly is an important defoliator which belong to Colaphellus genus of Chrysomelidae family and of Coleptera order. Recently, there were many pestises caused by Colaphellus bowringi Baly in China and they trended to be more harmful day by day. By far, the happening regularity and life history of Colaphellus bowringi Baly in Hei Longjiang province had not been studied in detail. To master the life history, main biological habits and genesis states of population in fields of Harbin, and to made accurate protective strategies, we systematically studied happening regularity, life history and diapause induction of Colaphellus bowringi Baly in Harbin from 2006 to 2007. The results were as follows:1. Observation of life history and habitMost individuals produced one generation per year, but a few individuals could produced two generations per year. The pest hibernated as adult in the soil. The diapaused adults burrowed in soil to depths of 2~27cm. The diapaused adults began to appear from the soil in late April the next year. The first generation happened from early May to early July. The second generation occurred from mid-June to mid-July. All adults beetles burrowed in soil to hibernate since the end of July. The adults burrowed in soil to depths of 2~27cm, most in depth of 5~13cm. At 25℃, the egg-laying period of females was 6-55d, the average was 30.95d. The individual female could produce 454.9 eggs on average.2. The effect of environment factors on the growth and survival of Colaphellus bowringi Baly(1) The effect of illumination on the growth and survival of Colaphellus bowringi Baly. At 25℃and 28℃, survival of Colaphellus bowringi Baly larvae in different photoperiod had no significant change. survival larvae at 25℃in different photoperiod were slightly higher than that at 28℃, so survival of Colaphellus bowringi Baly larvae was more affected by temperature, less affected by photoperiod.(2) The effect of temperature on the growth and survival of Colaphellus bowringi Baly. At 25℃, developmental duration was 4.46±0.33d in the egg stage, 8.22±0.26d in the larval stage, and 4.17±0.22d in the pupal stage. Developmental threshold temperature was 10.80±1.7℃for eggs, 10.95±2.1℃for larvae and 9.79±1.7℃for pupae. The effective accumulative temperature was 64.82±8.9 day-degrees for eggs, 117.31±20.9 day-degrees for larvae, and 64.36±8.4 day-degrees for pupae.(3) The effects of host-plants on growth and survial of Colaphellus bowringi Baly. Survival of Colaphellus bowringi Baly that were feeded different plants had significant difference.At 25℃(28℃), survival of Colaphellus bowringi Baly that were feeded with Raphanus sativus was lowest, 11.61(16.87), and Lepidum sativum L was highest , 98.71%(96.7%); host-plants had significant effect on developmental duration in the egg stage, Brassica napus L was was longest, 4.46±0.33d, and the shortest was Lepidum sativum L, (7.69±0.41)d.3 Effect of photoperiod on the diapause inductionThe diapause responses of Colaphellus bowringi Baly to different photoperiod at different temperature (20℃, 22℃, 25℃, 28℃, 30℃) was investigated. The results showed that the diapause response curves change not too much, while the proportion of diapause decreased with temperature increasing. The critical dark duration is between 8-10 h.4 Effect of temperature on the diapause inductionThe diapause responses of Colaphellus bowringi Baly to different temperature in continuously dark rearing condition and fixed photoperiod (LD14:10) were investigated. The result showed that the temperature could induce diapause.5 Effect of host-plants on the diapause in duction.The incidence of diapause was investigated by feeding the Colaphellus bowringi Baly with differenr host-plants at 25℃and 28℃, combined with 14:10(L:D). The result suggest that the incidence of diapause differ with diffenent host-plants. It was highest when feeded with Raphanus sativus, followed by Brassica pekinensis,Brassica jincea L,and Lepidum sativum L , Brassica napus L was the lowest.
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