天敌花绒寄甲与寄主松褐天牛成虫出现期的关系

Relationships between the Emergence of Dastarcus helophoroides(Coleoptera:Bothrideridae)and the Emergence of the Host Monochamus alternatus(Coleoptera:Cerambycidae)in Pinus massoniana Forests

【目的】明确天敌花绒寄甲与寄主松褐天牛成虫出现期的关系,为推广该天敌防治松材线虫媒介松褐天牛提供基础信息。【方法】通过在江西新干林间马尾松诱木上释放花绒寄甲,研究该天敌与寄主松褐天牛的羽化出孔规律;采用松褐天牛信息素诱芯诱捕,监测林间花绒寄甲与松褐天牛飞行活动的季节性动态;调查花绒寄甲成虫在枯死木上的分布规律。【结果】越冬结束后花绒寄甲成虫即可交尾产卵,繁殖下一代。越冬代松褐天牛成虫羽化出孔期为5月上旬至7月上旬,高峰期在5月下旬。第1代花绒寄甲成虫于6月底或7月初羽化出孔,7月下旬羽化结束,其平均羽化出孔期和羽化盛期分别为30.5天和11.5天;出孔高峰期在7月上中旬,这比越冬代松褐天牛成虫的晚42~50天。松褐天牛成虫的诱捕期从4月底开始到10月中旬结束,盛期在5月下旬至7月下旬;高峰期在6月中下旬。花绒寄甲成虫诱捕从5月上旬开始,5—6月诱捕到的成虫数量很少,仅占全年诱集量的6.62%;7月花绒寄甲诱捕量明显增多,诱捕高峰期在9月上中旬,这比松褐天牛的晚近3个月;7—10月的寄甲诱捕量占93.38%。花绒寄甲成虫主要分布在枯死木树干的中部和上部,以上部数量最多,占77.12%,其余在中部。第1代松褐天牛幼虫侵入孔数量在枯死木树干上部的比例为55.33%,中部为37.18%,下部仅为7.49%。【结论】越冬结束后花绒寄甲成虫就可交尾产卵,这就使第1代花绒寄甲幼虫的孵化期恰好和寄主松褐天牛发育到最适宜被寄生的蛹期相吻合,这是二者长期协同进化的结果,也表明花绒寄甲是一种专性寄生天敌。越冬代松褐天牛成虫5月初陆续羽化出孔后迁飞到健康松树上取食为害,并在危害木上产卵。第1代花绒寄甲成虫6月底或7月初陆续羽化出孔后,飞翔搜寻有第1代松褐天牛幼虫为害的枯死木栖息和越冬。花绒寄甲成虫在枯死木的分布位置主要在树中部和上部,以上部数量最多,且与松褐天牛的基本相一致。这说明花绒寄甲对寄主天牛具有很强的搜索追踪和跟随效应。

【Objective】The present study aims to investigate the adult emergence relationships between Dastarcus helophoroides and its host Monochamus alternatus in Pinus massoniana forests.The result would provide valuable information for applying the parasitoid to control the cerambycid beetle M.alternatus.【Method】The adult eclosion and emergence regularity of D.helophoroides and M.alternatus was investigated by releasing D.helophoroides eggs on the M.alternatus larvae and pupae of the infested bait-trees.The flight seasonal dynamics of D.helophoroides and M.alternatus adults was monitored using M.alternatus pheromone lures in the pine forests from 2016 to 2017.The distribution characteristics of D.helophoroides adults on pine trunks were surveyed by dissecting the dead pine trees.【Result】D.helophoroides adults could mate and lay eggs soon after overwintering.The overwintered adults of M.alternatus emerged in early May,and disappeared in early July with the peak in late May.The first generation of D.helophoroides adults emerged around late June and early July,and disappeared in late July;the peak of emergence was around early and mid July,which was 42-50 days later than that of the overwintered M.alternatus adults;and the average emergence period and the peak emergence duration were 30.5 d and 11.5 d,respectively.The M.alternatus adults were caught from late April to late October,and the high occurrence period was from late May to late July with the peak in mid June.The D.helophoroides adults could be caught by the M.alternatus pheromone lures from early May to mid October.Approximately 6.62%of the total number of the beetles were caught from May to June.The number trapped increased significantly in July,and reached the peak period in September,which was about three months later than that of M.alternatus adults trapped;Around 93.38%of the total number were caught from July to Octobert.The D.helophoroides adults were mainly distributed in the middle and upper parts of the dead tree trunks,with the upper part accounting for 77.12%of the total.The number of the boring holes by M.alternatus larvae were 55.33%distributed in the upper part,and 37.18%in the middle,and only 7.49%in the lower part.【Conclusion】The D.helophoroides adults enter the breeding season soon after overwintering,which makes the larval emergence period of the first generation D.helophoroides coincide with the optimum pupa stage of M.alternatus,which is the result of a long-term co-evolution of the two species.It is indicated that D.helophoroides could be an obligate parasitoid of M.alternatus.The M.alternatus adults of overwintered generation emerge after May,then emigrate to healthy pine trees for feeding and lay eggs later on the harmed trees.The D.helophoroides adults of the first generation emerge after June,then migrate and transfer to the newly-died wood bored by the M.alternatus larvae of the first generation.The parasitoid adults are mainly distributed in the middle and the upper part of the dead tree trunks,and the distribution pattern coincides basically with that of M.alternatus larvae.It could be concluded that the D.helophoroides adult has a significant tracking and following effect on its host.