海榄雌瘤斑螟的生物学特性及Bt对其幼虫的毒力和防效

海榄雌瘤斑螟(Acrobasis sp.)是危害马鞭草科澳洲海榄雌(Avicennia marina var.austrasica)的主要害虫.在深圳红树林一年发生6~7代,每个世代25~32d,其中幼虫历期13~16d,蛹5~6d,成虫7~10d,卵3~5d.幼虫剥食海榄雌的叶肉,8月低龄幼虫蛀食嫩芽及种子,10月低龄幼虫开始在嫩芽内越冬,翌年3月上中旬,越冬幼虫开始活动.每年4月下旬至6月中旬爆发的第2代和第3代密度较大,造成海榄雌大面积危害.在室内,用Bt感染2龄海榄雌瘤斑螟,致死浓度(C)-死亡几率值(Y)测定的回归线为Y=4.66 1.78C,80%的致死浓度LC80为4.60IU/mL;致死时间(T)-死亡几率值(Y)测定的回归线为Y=4.305T-1.51,80%的致死时间LT80为50.86h.在林间,用8~10IU/mL的Bt稀释液喷雾对海榄雌瘤斑螟进行防治实验,平均防效为90.61%.图3表5参8

Biological Characters of Ptyomaxia sp. And the Toxicity and Effectiveness of Bacillus thuringiensis Against Its Larvae

The larva of Acrobasis sp., which is the main pest of Avicennia marina var. austrasica, eats mesophyll of A. marina var. austrasica. Acrobasis sp. has 6~7 generations per year in mangrove forest at the Shenzhen Bay. 25~32 days are needed to complete one generation, 13~16 days for larvae, 5~6 days for pupae, 7~10 days for adults and 3~5 days for eggs. From the end of April to the middle of June, the second and third generations of Acrobasis sp. outbreak and cause great damage. Bt was used to control the second instar of Acrobasis sp. and study its effect on Acrobasis sp. indoors. The linear regression equation of lethal concentration(C)-mortality(Y) value was Y=4.66 1.78C, and the lethal concentration of 80% (LC80) was 4.60 IU/mL. The linear regression equation of lethal infected time (T)-mortality (Y) value was Y=4.305T-1.51, and the lethal infected time of 80%( LT80) was 50.86 hours. Ptyomaxia sp. was controlled with Bt at the concentration of 8~10 IU/mL in mangrove forest, and the average lethality was 90.61%. Fig 3, Tab 5, Ref 8