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Development of the Parasitoid Microplitis rufiventris Reared in Hosts Treated with Lefenuron, a Chitin Synthesis Inhibitor

Published online by Cambridge University Press:  19 September 2011

E. M. Hegazi ,
A. M. El-Minshawy ,
W. E. Khafagi  and
N. El-Singaby
E. M. Hegazi*
Affiliation:
Department of Entomology, Faculty of Agriculture, Alexandria University, Egypt
A. M. El-Minshawy
Affiliation:
Department of Entomology, Faculty of Agriculture, Alexandria University, Egypt
W. E. Khafagi
Affiliation:
Plant Protection Research Institute, Sabahia, Alexandria, Egypt
N. El-Singaby
Affiliation:
Department of Entomology, Faculty of Agriculture, Alexandria University, Egypt
*
Corresponding author: EMH.
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Abstract

Eggs and larvae of Microplitis rufiventris Kok. (Braconidae: Hymenoptera) were exposed to two sublethal concentrations (0.2 and 0.4 ppm) of the chitin synthesis inhibitor lefenuron, by feeding treated artificial diet to their hosts, Spodoptera littoralis (Boisd.) (Noctuidae: Lepidoptera) larvae. Each concentration was initiated during the egg stage or different instars of the parasitoid larvae. Between 4.3 and 33.8% of parasitoid larvae in lefenuron-treated hosts showed morphological and developmental abnormalities. The effect of the compound on the developmental rate and sensitivity of the parasitoid larvae varied according to the parasitoids' age at treatment; the egg stage and older parasitoid larvae were more tolerant to the compound than the first instars. In all treated hosts the developmental rate of the parasitoid was lower than that of controls. The lower lefenuron concentration (0.2 ppm) was more effective at disrupting the development of young parasitoid larvae than the higher one. Delayed or latent effects of the compound were evident in non-emergence of parasitoid adults that were exposed to the compound as first instars. Reduced sensitivity of old parasitoid larvae could be compatible with survival of the parasitoid in integrated control programme of S. littoralis.

Résumé

Les oeufs et larves de Microplitis rufiventris Kok. (Hymenoptera: Braconidae) étaient exposés á deux concentrations sub-létales (0,2 et 0,4 ppm) de lefénuron, un inhibiteur de synthèse de la chitin, par alimentation sur milieu artificiel des chenilles de Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) qui sont des hôtes du braconidé. Chaque dose était administrée au stade oeuf ou á des différents stades larvaires du parasitoïde. Les chenilles nourries au lefénuron ont révélé entre 4,3 et 33,8% de larves mal développées du parasitoïde et possédant des anomalies morphologiques. L'effet du lefénuron sur le taux de croissance et de développement ainsi que sur la sensibilité des larves variaient avec l'âge du parasitoïde, au moment du traitement. Les oeufs et larves âgées du parasitoïde étaient plus tolérants vis-á-vis du produit plus que les jeunes stades. La basses concentration du lefénuron pertubait le développement des jeunes larves plus que les concentrations élevées. L'arrière-effet et la latence du produit étaient manifestes et ils étaient reflétés par la non-émergence des adultes chez les larves exposées au produit á leur premier stade de développement. Dans un programme de lutte intégrée contre S. littoralis, une sensibilité réduite des larves âgées du parasitoïde pourrait présager une survie du parasitoïde.

Keywords

Spodoptera littoralisMicroplitis rufiventrislefenuronendodevelopmental rateSpodoptera littoralisMicroplitis rufiventrislefénurontaux de développement interne
Type
Research Articles
Information
International Journal of Tropical Insect Science , Volume 19 , Issue 2-3 , September 1999 , pp. 199 - 206
Copyright
Copyright © ICIPE 1999

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