刺桐釉小蜂(膜翅目: 釉小蜂科)之寄生蜂在田間發生情形及其寄生性旋小蜂Eupelmus sp.(膜翅目: 旋小蜂科)生活史

Abstract

Quadrastichus erythrinae Kim is a serious gall inducing invasive pest in recent years. Female lays eggs in the tissue of young leaves and shoots of coral trees (Erythrina spp.). After larvae hatched from eggs, they develop in host tissue, causing swelling and curling of the infested parts. Severe infestations will influence host health and even cause the death of hosts. The invasion of Q. erythrinae devastated coral trees in many places of Taiwan, including some elder trees. Up to date, the main method to against Q. erythrinae relies on chemical control. However, insecticide resistance may be induced when applying chemical control for a long time. Therefore, developing biological control may provide a better strategy for a long term concern and applying native enemies will cause less environmental impact compare to introduced ones. According to previous investigation, there are several parasitoid wasps use Q. erythrinae as a host. One of them is Eupelmus sp. (Eupelmidae) which distributes widely in Taiwan. However, little knowledge of its biology has been established. The life cycle of Eupelmus sp. was studied in this research to help estimate its potential as a biological control agent. Besides, the occurrences of other parasitoids were acquired through the investigation of Q. erythrinae in Taiwan for adding other choices in biological control. Two other species of wasps on Q. erythrinae were found in Taiwan through dissecting wild galls and rearing the parasitoid wasps. One belongs to Megastigmus sp. (Torymidae), and the other is Aprostocetus sp. (Eulophidae). Lab experiments showed that Eupelmus sp. will lay eggs when provided Q. erythrinae galls at 17 to 20 developmental days. It takes about 21 days for a euplemid wasp to develop from egg to adult in 25℃. Male biased was found in both lab rearing and wild Eupelmus sp. When offering different foods, adult longevity of males is longest in both treatments of 10% honey and honeydew of coral trees. Morphological characteristic measurement showed that females collected from wild is bigger than females emerged from Q. erythrinae galls. It suggests that the female collected in wild may not developed on Q. erythrinae. For mass rearing and control application, it is crucial to find out original hosts of Eupelmus sp. in Taiwan as the information is useful for developing effective rearing techniques and increase the control potential. Analysis of monitoring data shows that the occurrence time between Aprostocetus sp. and Eupelmus sp. did not overlap to each other and, therefore, a biological control strategy using both parasitoids may provide a compensatory effect to increase the control efficiency. Although the parasitoid wasps of Q. erythrinae so far found in Taiwan are less host specific, they have stably occurred on the population of Q. erythrinae. It suggests that there is a potential for applying parasitoid wasps as agents of biological control against Q. erythrinae in Taiwan.