| The eulophid wasp Diglyphs isaea, a larva ectoparasitoid of a number of agromyzid leafminers on herbaceous plants, is a dominant natural enemy of vegetable leafmininers in Beijing area. To make use of this species, behaviour character, development and fecundity, functional response, feasibility of laboratory mass rearing of the parasite were investigated. Volatiles from different plants were identified by GC-MS and active bioassays of the volatile components were carried out in laboratory.Female D. isaea stinged and oviposited 1-3th hosts to feed upon the exudates. 2-3th instar hosts were more suitable for the parasite development and prefered by the parasite. The process of the parasite oviposition behavior of D. isaea was divided into four major stages: host location, host examination, oviposition and host feeding, trimming. Adult eclosed during morning hours, with males a little bit earlier than females. Temperature affected eclosion continuing time and peak times. Generally, the time consumed for eclosion decreased with the increased temperature and their peak times occurred earlier. Mating usually occurs within 24 hours after eclosion. Both females and males were capable of mating more than one time. The parasitic activity of D. isaea mainly occurred in photophase. When provided with honey, the longevity of D. isaea was significantly prolonged.Effects of temperature on development of the parasitoid were investigated, using Liriomyza huidobrensis (Blanchard) and Liriomyza sativae (Blanchard) as the host and Bush Kidney Bean ( Phaseolus vulgaris) as the host plant. The development of the parasitoid was significantly affected by temperature. The developmental threshold temperature of D. isaea, estimated from linear regression equations between temperature and developmental rate, for the egg-larva, pupal and total combined life stages were 10.41C, 7.72C, 9.29C on L sativae, and 10.44 C, 8.49C, 10.40C on L huidobrensis, respectively. Degree-day values for the egg-larva, pupal and total combined life stages were 90.62, 88.59, 178.27 degree-days on L. sativae, and 91.60, 107.75, 170.00 degree-day's on L. huidobrensis,respectively. Mean development times of D. isaea pupae were usually slightly shorter than that of egg-larva. The longevity of adults and the average number of eggs per female were 22.67d and 252.6 eggs on L. sativae and 23.00d and 241.0 eggs on L huidobrensis, respectively. The number of killed host larvae on L. sativae and L. huidobrensis were 304. 1 and 242. 2, respectively.A method, using L. huidobrensis as the host and Broadbean (vicia faba) as the host plant in greenhouse, was developed for mass rearing D. isaea. 12 pots of Broadbean were exposed to 250 adult L. huidobrensis for oviposition, which produced 796 host larvae per cage. Plants containing late second to early third host instar were exposed to 50 female D. isaea in parasitic colony cages for 2d. 270 parasites emerged per cage, and the emergence rate of parasite was 34%. 20 pots of Broadbean, which containing 1488 late second to early third host instar, exposed to 80 female D. isaea, the mean emergence parasites is 358.2 per cage. The suitable proportion of the parasitoid to host was 1:13-20 (30+40+50cm ) in mass rearing. The optium temperature for rearing parasite was 18-30C. Based on above rearing procedure, The price of per D. isaea was estimated to be 0.04 yuan. The functional response of host density by D. isaea was studied with L. sativae and L. huidobrensis. The result showed that the density of host larvae significantly affected the parasite effect of D. isaea. The number of killed host larvae decreased as the number of host larvae increased.Olfactory response of D. isaea to plant volatiles were studied in laboratory. Volatiles emitted from Broadbean, Bush Kidney Bean (Phaseolus vulgaris), Oilnavew Bird Rape (Brassica campestris), Pakehoi (Brassica Chinensis), Wild Cabbage (Brassica oleracea) were extracted by cold-trapping devices and Tenax GR. Olfactory response of D. isaea to the volatiles was measured by a... |
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