Studies On Biology Of The Brown Marmorated Stink Bug Halyomorpha Halys (St(?)l) (Hemiptera: Pentatomidae), An Important Pest For Pome Trees In China And Its Biological Control

The brown marmorated stink bug, Halyomorpha halys (St?l) (Hemiptera: Pentatomidae), is an severe pest both in orchard and ornamental trees. Its nymphae and adults attack many pome fruits e.g. pear, peach, apple and so on. Particularly, pear was attacked heavily in north China. The pest brings great loss to fruit grower. The bug was a recently introduced pest to the western hemisphere. This stink bug could become a major agricultural pest in North America.At present, the studies on the pest mainly focus on its biology, control techniques by pesticide. Because the pest has many hosts and could move from forest trees to fruit trees freely. It brought difficulties for controlling it by normal techniques. In order to produce"green fruits", it has to control the pest with nonpolution and nontoxicity measures. Thus, we conducted biocontrol study on using its natural enemies. The research results are as follows.(1) The life cycle and biology of H. halys were studied by investigation in both field and the laboratory. It was found that the bug has 2 generations per year and overwintered as adult. In late March, it began to act, and mates in the early May. Most female adults oviposit from late May to mid June and mid July to early August. In late August some adults become to overwinter. A female oviposited 4 egg mass with 82 eggs maximally. Eighty percent of egg mass contain 28 eggs each mass.(2) The natural enemies attacked the bug in its each stage have been investigated. A total of 9 species of natural enemies were found, including 6 parasitoids: Trissolcus halyomorphae Yang (Hymenoptera: Scelionidae), Trissolcus sp., Telenomus sp., Acroclisoides sp., Anastatus sp., Ooencyrtus sp., Orius sp. (Hemiptera: Anthocoridae), Arma chinensis (Fallou) (Hemiptera: Pentatomidae) and Misumena tricuspidata (Araneida: Thomisidae). The predominant natural enemy of the pest was T. halyomorphae. Its parasitism rate could reach 20～70%, on an average 50%.(3) The parasitoid T. halyomorphae was the important natural enemy of the bug. Its biology showed that the wasp was a solitary parasitoid and its male emergence earlier than female, and they mated soon after emergence. Then the female seeked her host and oviposited. A female could lay 40.6 eggs averagely. Its female prefered newly-laying host eggs. Developmental period and longevity of the wasp adult were closely related to temperature. The fast developmental period occurred at 30℃with 7.3±0.17 days. The developmental zero and effective accumulated temperature were 12.2℃and 132.5 day-degrees respectively. Supplementary nutrition could remarkably delay adult wasp's longevity. The adults could live 43.93±2.72 days for female and 33.29±2.52 days for male in average when fed with 20% honey solution. The peak periods for the wasp population were appeared at the mid and last ten-days of June, the last ten-days of July and the first ten-days of August.(4) The interspecific competition between T. halyomorphae and Anastatus sp. were studied in the laboratory at 25℃. The both parasitoids could lay egg into host egg previously parasitized by the other species, which caused multiparasitism. The result showed that when the host egg was parasitized by T. halyomorphae for≤4 days first, and then exposed to Anastatus sp. for oviposition, finally near all emerged parasitoid from the host egg were Anastatus sp., the host eggs were parasitized by T. halyomorphae for≥6 days first, then T. halyomorphae adult wasps were emerged mostly. Contrarily, when the host eggs were parasitized by Anastatus sp. for≤one day first, and then were exposed to T. halyomorphae for oviposition, finally most of emerged wasp adults were T. halyomorphae. But the host eggs were parasitized by Anastatus sp. first for≥2 days, and then exposed to T. halyomorphae, near all emerged wasps were Anastatus sp. from the host eggs. It was indicated that the two egg parasitoid species has serious host competition.(5) It was found that with cold constant temperature 7℃and 11℃for storage, the eggs and the larvae of T. halyomorphae could not tolerent. But the temperature for storage of its pupa was feasible. When the female adults were stored at 11℃for 19 weeks, the survival percentage of the parasitoid was 90%. The survival percentage of the female adults stored for 17 weeks at 7℃was above 50%, and the percentage survival of the female adults under 50% at 4℃for 3 weeks. However, the life-span of male were shorter, and the survival percentage of the male stored for 4 weeks at 7℃was below 50%, and all died at 8th week. The male adults died at 4℃storaged for 3 weeks. At 11℃, the survival percentage of the male adults stored for 7 weeks was below 50%, and all died at 10th week. The result showed that the functional response was in keeping with Holling's type II, the mathemical model of functional response was Na= N/(0.6485+0.01343×N), the theory maximum numbers of parasitism was 74.45 eggs. (6) The mass rearing techniques of the egg parasitoid were tested in laboratory. It was showed eggs of Erthesina fullo Thunberg, Eurydema dominulus(Scopoli), Dolycoris baccarum (Linnaeus), Arma chinensis(Fallou) and Plautia crossota(Dallas)were all substitute hosts.(7) The eggs of Antheraea pernyi (Lepidaptera: Saturniidae) was tested for mass rearing the parasitoid. The eggs were besmeared the acetone of eggs of the bug and the secretion of the bug female, then the parasitoid female were attracted. Although it was found that the female parasitoid pricked the eggs and seemed to lay egg in, finally there were no one wasp emergen- ced from the parasitized eggs. It is necessary to study the reason later.The natural enemies attacked the bug in its each stage have been investigated. The predominant egg parasitoid of the pest was T. halyomorphae. Its biology and ecology were investigated. The interspecific competition between T. halyomorphae and Anastatus sp. were studied, especially the technique of the mass rearing the parasitoid with substitute hosts. These were the base to biocontrol the bug. It is necessary to study the technique of releasing the egg parasitoid later.