Studies On Parasitoid Species Of The Leafminers Liriomyza Spp.and Chromatomyla Horticola Goureau And Their Biology And Ecology

The parasitoids of the vegetable leafininers, Liriomyza spp. and Chromatomyia horticola Goureau were surveyed and studied during 1999-2000 in the vegetable areas of Hangzhou , China; and a preliminary biological study of the dominant species, Opius caricivorae Fischer was also carried out in laboratory. The major results are summarized as follows.A total of 14 parasitoid species, i.e. Opius caricivorae Fischer N Chrysocharis pentheus (Walker) , Teleopterus erxias (Walker) , Diglyphus albiscapus Erdos , Diglyphus sp. , Neochrysocharis punctiventris (Crawford) , Neochrysocharis formosa (Westwood) N Pediobius pyrgo (Walker) , Closterocerus trifasciatus Westwood , Tetrastichus char a Kutju , Pnigalio katonis (Ishii) , Cirrospilus lyncus Walker , Magaspilus sp. and Pachyneuron sp., were reared from the larvae and pupae of the leafminers, Liriomyza sativae Blanchardx Liriomyza chinensis (Kato) and Chromatomyia horticola Goureau. Among these, O. caricivorae and C. pentheus were the dominant species in the different stages. Pachyneuron sp. was the hyperparasitoids of O. caricivorae. Seven parasitoids, i.e. O. caricivorae, C. pentheus , P. katonis , N. punctiventris , N. formosa, Diglyphus sp. and Pachyneuron sp. were first recorded from Liriomyza chinensis (Kato) in China as well as in the world, and O. caricivorae is a new record to China. The parasitism of the parasitoids on the leafminers in the untreated plots could reach 69% at the later growing stages of vegetables. It is concluded that the parasitoids play a very important role in the natural control of the leafminers.The length of cephalopharyngeal of L. sativae can be used as a criterion for distinguishing larval instars, and the length of the miners can be used to judge the larvalinstars at 4 constant temperatures from 21癈 to 30癈.O. caricivorae parasitized all 3 instars of L. sativae, but preferred to parasitize the 2nd and 3rd instars when it was exposed to the 1st, 2nd and 3rd instar L. sativae larvae concurrently. The preference indexes to the 1st, 2nd and 3rd instar were 0.24, 0.35, and 0.41, respectively. The result also suggested that the control efficacy of the parasitoids included both successful parasitism and death caused by the parasitoids' repeated, unsuccessful attacks.The relationship between the rates of development of the parasitoids' eggs, larvae and pupae with temperature followed the linear equations or the logistic curve.The threshold temperatures for the development of eggs, larvae and pupae were 9.46癈, 8.86癈 and 6.73癈, respectively. The developmental effective accumulated temperatures for eggs, larvae and pupae were 37.5, 103.1 and 135.1 day-degrees, respectively. One generation needed 270.3 day-degrees above 8.14癈.Females of O. caricivorae were not able to distinguish if a larve was parasitized or not. They could oviposit 1-7 eggs inside one host larve, but only a parasitoid could develop from it. The number of larvae parasitized and attacked increased with increase of larvae density.The sex ratios of females of O. caricivorae to males range commomly from 0.68 to 2.67, but sometimes they could reach 5 or 15 when the hosts were provided in 2nd or 3rd instar respectively.