Studies On The Occurrence And Injury Of Quadrastichus Erythrinae Kim And Its Chemical Control

Erythrina gall wasp (EGW), Quadrastichus erythrinae Kim, is a new quarantinable gall-inducing invasive pest. Since its first occurrence in 2003, the pest has spread to several tropical and subtropical countries in Pacific islands and continental margins of Asia or North Amrica. This paper dealt with the oviposition preference, distributions of galls and adaption to temperature extremes of EGW. Based on which, a geographic distribution model for EGW was established and the chemical control was discussed. The results were shown as follows:1. EGW produced by amphigenesis. The process of oviposition included 4 steps. The females began to lay eggs at the second day after copulating with a peak at the third day. The females preferred to oviposit on tender leaves of the length of 1-2cm while didn't lay on the leaves over the length of 3.5cm. The pest damaged to produce galls generally on young shoots, primarily leaves and petioles, but sometimes on tender stems of Erythrina variegata var. orientalis. The host preference for oviposition was significantly different among the hosts tested. E. variegata var. orientalis and E. variegata cv.'Parcellii'were more preferred than E. variegata. No eggs were found on E. cristagalli by delivering adults in the laboratory.2. The study on the distributions of galls induced by EGW on E.variegata var. orientalis leaves indicated that: galls on leaves mainly located at the lower parts beside the main vein near the petiole; the frequency of the galls appearing in one and two-galls group was more than 50%; the spatial distribution of the galls on leaves was aggregating based on the spatial pattern parameters, and its basic element of distribution was clusters of individuals which increased with the gall density; the aggregation degree was dependent on the gall density; the aggregation was caused by the environment condition and the congregation habit of insect.3. The adults had strong adaptability to high temperature. About 10% of adults can survive under the treatment of 43℃for 1h, and the adults almost died after the treatment of 37℃for 12h or 40℃for 6h; the longevity of adults decreased with the increase of exposure time; the maximum effect of hot acclimation was achieved under 37℃for 1h; the mean supercooling point (SCP) of adults was -9.6℃; the treatment of exposure under 6℃didn't decrease the mean SCP significantly.4. The potential geographical distribution model of EGW in China showed that: the pest could exist in 59.40% regions of China, and was more likely to occur 3 to 6 generations yearly in suitable survival regions; the potential geographical distribution could be divided into security areas (accounted for 40.60%), mild dangerous areas (22.69%), dangerous areas (23.73%) and high-risk areas (12.99%); South China Region and partial areas of Yunnan, Zhejiang, Jiangxi Province which had the shortest bio-climate similar distance (dij=0.6) with the standard point were most likely to be invaded by EGW.5. The field bioassay of four kinds of systemic insecticides for trunk injections was conducted against EGW. The results showed that Chongxianqing and avermectin could be more effective than imidacloprid and acetamiprid with lower damage rate, lighter gall weight, fewer adult emergence within 3 months. Imidacloprid and acetamiprid had the worst results with little effect on EGW after 3 months. The control results of soil drenching had no more difference with that of trunk injecting.