Studies On Biological Characteristics And Cold Tolerance Of The Tetrastichus Planipennisi

The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera:Buprestidae:Agrilus) is an important wood-boring beetle attacking ash trees (Oleceae:Fraxinus spp.). In the 1960s', EAB severely infested F.americana and F.pennsylvanica in the northeast regions of china. In recent years, the tendency of the EAB's harm has exacerbated.Tetrastichus planipennisi Yang is an important natural enemies endoparasitized the larvae of Agrilus planipennis in northeast of china. For the better use T. planipennisi to control the damage, the harm characteristics and life history of the EAB were investigated in Liaoning province, meanwhile, the Tetrastichus planipennisi's biology characteristics and cold hardiness were studied, the main results and findings were as follows.The life cycle and biology of EAB were researched using methods of observatory in laboratory and regular investigations in the forest. Results indicated that the EAB developed one generation per year and overwintered as mature larval in shallow chamber and young larval in cambium. Adults began to emerge in late May, with a peak in early June. The second emergence continued from late July to late September.The life cycle and biology of T. planipennisi were studied using methods of measurement developmental threshold temperature and effective accumulated temperature and regular investigations in forest. The results showed that the threshold were 7.98±1.15℃,11.0±0.67℃12.2±1.04℃for egg-larval stage, adult male pupae and female pupae. The effective accumulated temperature were 204.13±12.92 d·℃,129.7±5.68 d·℃,126.4±9.31 d·℃, respectively. In liaoning province, T.planipennisi developed three generations per year and overwintered as mature larval inside the host gall, the wasp eclosion in middle May next year.Under the constant temperature of 21℃,25℃,31℃; the effect of temperature and nutrition on the adult longevity of T. planipennisi were studied in laboratory. The results show that adult longevity had significantly difference under different temperature conditions and decreased with the higher temperature. Nutrition can effectively prolong the adult longevity. Under the different temperature conditions, adult longevity is not always with have consistent with the concentration of nutrient solution. The adult have longest longevity were feed 20% nutrition solution at 21℃, however, at 25℃,31℃, the adult were feed 15% and 10% nutrient solution have the longest longevity. At the same conditions, the longevity of female was longer than the male.Using the super cooling point and morality of exposed in low temperature to evaluate whether the super cooling point could indicate the cold hardiness. The results showed that super cooling point and mortality at low temperature of T.planipennisi have a higher consistency, super cooling point can be used as an indicator of cold hardiness. On this basis, super cooling point were measured at different cooling rates of 1℃/min and 5℃/min. The results indicated that using these two different cooling rates did not have a significantly influence to the results.The cold hardiness of overwintering individuals of T.planipennisi and Agrilus planipennis Fairnaire were measured and compared by the super cooling point (SCP) and freezing point (FP). The results indicated that the super-cooling point and freezing point of T.planipennisi ranged from-25.21℃to-24.17℃and form-18.98℃to-16.81℃, respectively; and of Agrilus planipennis Fairnaire ranged from-26.13℃to-24.79℃and form-21.24℃to-19.28℃.Both have strong cold hardiness.The super cooling point of the T. planipennisi of the different instars and month were measured in order to clarify the cold hardiness of its different developmental stages. The results showed that significant effects of different instars on SCP were observed that mean SCP were 4.7℃lower of the larval than the pupa, so overwintered as the mature larval. Mean SCP values of the larval in September 2009, January, March, May 2010 were-20.72℃,-25.46℃,-24.19 and-21.33℃, respectively. The value was significantly lower in March, May 2010 than September,2009 and May 2010. These changes of the SCP have the coincidence with rhythm of seasonal changes in temperature.Through these investigations and researches, the biology characteristics and cold hardiness of the emerald ash borer and its important parasitic nature enemy T. planipennisi have been further master as well as the relationships between the two insects. These findings would provide the theory for prevention and cure of the EAB.