Medfly eradication in California:

The impact of malathion-bait sprays (directed against medfly, Ceratitis capitata [Wiedemann]) on an endemic gall midge (Rhopalomyia californica Felt) and its parasitoids was investigated during 1982–83 in the south San Francisco Bay area of northern California. In a heavily sprayed area (Woodside), a population explosion of the midge was detected following 24 applications of malathion bait. The midge population reached levels ca. 90x greater than those observed in an adjacent unsprayed area (Jasper Ridge). In a moderately sprayed area (Portola Valley), the midge population increased as much as 5x that observed in the adjacent unsprayed area (Jasper Ridge), following 12 applications of malathion bait. In laboratory tests, the malathion bait was toxic to both the midge and its parasitoids. The major parasitoids were Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica (Ashmead) and Mesopolobus sp. Population increases of the midge following malathion-bait sprays were attributed to destruction of parasitoids and other natural enemies of the midge. If the environmental impact of malathion-bait sprays is related to the number of applications (as suggested in this study), then it would be worthwhile to determine the appropriate bait-spray strategy for a given situation, so as to minimize adverse effects on nontarget species, yet insure suppression or eradication of medfly.

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Résumé L'impact des pièges tratiés au malathion (destinés à Ceratitis capitata Wiedem) sur Rhopalomyia californica Felt et ses parasitoïdes a été examiné en 1982–1983 dans le sud de la zone de la baie de San Francisco en Californie. Dans une zone fortement traitée (Woodside), une explosion de population a été décelée après 24 traitements. La population de R. californica a atteint des niveaux 90 fois supérieurs à ceux observés dans une zone contiguë non traitée (Jasper Ridge). Dans une zone modérément traitée (Portola Valley), avec 12 traitement, la population de R. californica a atteint jusqu'a 5 fois celle de Jasper Ridge. Au laboratoire, le piège à malathion a été toxique tant pour R. californica que pour ses parasitoïdes, dont les principaux étaient: Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica(Ashmead) et Mesopolobus sp. L'accroissement de la population de C. capitata après traitement a été attribué à la destruction de parasitoïdes et d'autres ennemis naturels. Si l'effet su l'environnement du traitement est lié au nombre d'interventions (comme le suggère cette étude), alors cela vaudrait la peine de définir une stratégie de traitement appropriée à une situation donnée, de façon à minimiser les effets négatifs sur des espèces non visées, tout en assurant la suppression ou l'éradication de C. capitata.

     

Host Location and Ovipositional Behavior of Platygaster demades Walker (Hymenoptera: Platygastridae), an Egg Parasitoid of Apple and Pear Leaf Curling Midges

The foraging responses of 1–2-day-old naïve female Platygaster demades to odors of apple and pear foliage and host insect eggs were measured. The host origin of P. demades had no effect on the parasitoids’ longevity, host preference, or foraging behavior. Four distinct behaviors related to oviposition were identified. In choice experiments, more female parasitoids responded to apple foliage with no midge eggs than to midge eggs alone. In a Y-tube olfactometer, parasitoids preferred the plant cues to clean air, and responded equally to both apple and pear odors. The results indicate that P. demades utilizes plant cues to locate the habitat of its host and then searches for host eggs to parasitize.     

外来入侵害虫刺槐叶瘿蚊的重要天敌——刺槐叶瘿蚊广腹细蜂

外来入侵害虫刺槐叶瘿蚊Obolodiplosis robiniae (Haldemann) 原产北美洲东部, 2006 年在中国发现, 危害刺槐叶片, 严重影响刺槐的健康生长, 已经列入我国检疫性害虫名单。在河北省秦皇岛市野外调查, 发现了一种广腹细蜂科天敌--叶瘿蚊广腹细蜂Platygaster robiniae Buhl and Duso, 该寄生蜂属中国新记录种。野外观察表明其对刺槐叶瘿蚊最高寄生率达84.8%, 具有良好的生物防治应用前景。本文对该广腹细蜂的外部形态和初步观察的生物学特性进行了描述。     

Female reproductive biology of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (Hymenoptera: Eulophidae), two parasitoids associated with the African Rice Gall Midge, Orseolia oryzivora (Diptera: Cecidomyiidae)

We investigated the female reproductive system of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (= Tetrastichus pachydiplosisae) (Hymenoptera: Eulophidae), two parasitoids associated with the African rice gall midge, Orseolia oryzivora (Diptera: Cecidomyiidae). Both optical and electron microscopy were used. The female reproductive system of P. diplosisae includes two large ovaries of the meristic polytrophic‐type, each composed of several tens of ovarioles. The system includes also a venomous gland that extends to a common oviduct. This gland had a filiform secretory portion, in which the epithelium was thin and surrounded a common evacuation canal. The secretory cells secrete into a large reservoir. Parasitism due to P. diplosisae is gregarious. The female reproductive system of A. procerae includes two ovaries of the meristic polytrophic‐type, and each ovary has a few ovarioles. Each ovariole includes one or two oocytes, which can be seen in the vitellarium. Two accessory glands, which extend to the oviduct, are also visible. The secretory epithelium of the accessory gland is made up of a dense network of secretory cells surrounded by muscle fibers. Females of A. procerae pierce the tissues of the gall and probably deposit one egg on or close to the pupa of the midge. Aprostocetus procerae is a solitary parasitoid of the midge. The two parasitoids exploit the same host at different developmental stages. These findings improve our knowledge of the reproductive biology of these two parasitoids associated with the African rice gall midge, an important pest in Africa.     

First field evidence that parasitoids use upwind anemotaxis for host-habitat location

The direction of flight of natural populations of Phradis interstitialis (Thomson), Tersilochus obscurator Aubert (both Hymenoptera: Ichneumonidae), and Platygaster subuliformis (Kieffer) (Hymenoptera: Platygastridae), parasitoids of three crucifer‐specialist herbivores, to and from their hosts’ host plant [oilseed rape, Brassica napus L. (Brassicaceae)] was studied in the field within a heterogeneous arable environment. Double‐sided Malaise traps encircling a plot of winter oilseed rape (cultivar Lutin) were used to sample the parasitoids as they flew towards and away from the plot during spring and summer. Daily trap catch of parasitoids and trap air flow were compared using Spearman's rank correlation. For all 14 insect days analysed, and for each species, the correlations between daily catch of parasitoids into distal halves of traps (relative to the plot) and wind direction were negative, significantly so on half the days analysed. This confirmed that flights towards the plot were by upwind anemotaxis. In contrast, the correlations between daily catch of parasitoids into proximal halves of traps (relative to the plot) and wind direction were most often crosswind; they were never strongly nor significantly either negative or positive. Implications of the results for integrated pest management strategies incorporating biological control with these parasitoids are discussed.     

外来种刺槐叶瘿蚊的重要寄生性天敌——刺槐叶瘿蚊广腹细蜂在中国的地理分布

刺槐叶瘿蚊广腹细蜂Platygaster robiniae Buhl and Duso(膜翅目:细蜂科)是我国外来有害生物刺槐叶瘿蚊Obolodiplosis robiniae(Haldeman)(双翅目:瘿蚊科)十分重要的寄生性天敌,为卵-幼虫跨期寄生蜂,专化性强,在自然抑制害虫虫口密度中起着非常重要的作用。为摸清刺槐叶瘿蚊广腹细蜂在我国的地理分布,探讨其与刺槐叶瘿蚊的相互关系,本文根据寄主刺槐叶瘿蚊在我国的分布范围,采用踏查的方法,对全国17个省、市、自治区的29个地区进行了调查。结果显示,刺槐叶瘿蚊广腹细蜂在其寄主分布区都有分布,分布范围在26°35.451′-43°53.482′N,103°51.816′-125°15.969′E,海拔4-1 097 m。