泡桐大袋蛾种群破产阈值的研究

对河南省兰考县１９８５～１９９５年泡桐大袋蛾发生和防治情况的分析结果表明：泡桐大袋蛾的发生可分为蔓延期（１９８５～１９９０年）、高峰期（１９９１～１９９２年）和破产消亡期（１９９３～１９９５年）．在发生蔓延期，大袋蛾年扩散速率平均为１１５％；在发生高峰期，全县受害，扩散速率接近０；在破产期，大袋蛾种群趋于灭亡．根基注射甲胺磷防治效果较好，飞机低容量或超低容量喷雾防治是控制大面积大袋蛾危害的最有效手段．不同虫口密度下大袋蛾损叶量没有显著差异，幼虫前４龄平均损叶量为１９１．７１ｃｍ２．不同虫口密度条件下饲养的幼虫，其百叶损耗平均用时有显著差异，其中密度为４００头／百叶时，百叶损耗平均用时为３１ｄ，２００头／百叶为５２ｄ，１００头／百叶为７１ｄ．该文提出了泡桐大袋蛾种群破产阈值的观点，并计算得到破产阈值指标ＴＣｒ＝３５５头／百叶，即当１～２龄幼虫虫口密度超过３５５头／百叶、扩散速率为０时，种群将自然、迅速地崩溃，这时的防治措施对大袋蛾种群消亡不起决定性作用．

Population Crash Threshold of Paulownia Bag-Worm

Data of Paulownia bag worm ( Clania variegata Snellen) population dynamics, management and larval density from 1984 to 1995 in Lankao county, Henan province were analyzed. The results showed that the development of bag worm could be devided into 3 stages: the spreading period(1985～1990), the peak period(1991～1992) and crash period(1993～1995). The average spreading rate of bag worm during spreading stage was 115% annually, i.e. the area attacked by bag worm in second year was two times of that in first year, and nearly 0 from 1991 to 1992, and then the bag worm population died out from 1993 to 1995. Root injection of Methamidophos had an effective efficacy for control of bag worm, though the operations can not hold back the spread of bag worm due to incomplete control. The best option for controlling bag worm is low volume or ultra low volume aerial spray of Deflubenzulon. Larvae consume 191.71 cm 2 Paulownia leaves on average from 1st to 5th instar. It took larvae averagely 31, 52, and 71 days to consume 100 Paulownia leaves under density of 400 ,200,100 larvae per hundred leaves, respectively. The larval density of population crash threshold T Cr =355 larvae per hundred leaves, i.e. the bag worm population will crash naturally and quickly under the condition of larval density=355 larvae per hundred leaves or above and spreading rate=0 .