Larvae mortality of Orgyia trigotephras Boisduval, 1829 (Lep.: Erebidae, Lymantriinae) in Tunisia


Abstract: Phytophagous insects feed on a plant or on a part of the plant. This choice is not only based on the nutritional content of the host plant, but also on the intensity of predation and parasitism. This work carried out in spring 2013 (mid-April, early June), aims to study the importance of larval parasitoids of Orgyia (Clethrogyna) trigotephras (Lepidoptera: Lymantriinae) in two sites Jebel Abederrahmane (North-East, Cap-Bon) and Sejnane (North-West, Bizerte) on two host-plants Quercus coccifera and Pistacia lentiscus. A total of 761 larvae of O. trigotephras of different instars were collected on both host-plants. In the laboratory, the caterpillars were individually placed in Petri dishes and reared on young foliage of Q. coccifera. Daily monitoring, allowed larvae mortality and parasitoids emergence. Morphological and molecular analyzes identified five parasitoids: Agrothereutes tunetanus (Hym.: Ichneumonidae) and Eupelmus seculatus (Hym.: Eupelmidae) where observed only on P. lentiscus in Jebel Abederrahmane. Microplictis nr sofron (Hym.: Braconidae) observed on both host-plants in Jebel Abederrahmane. An unidentified Eulophidae observed on Q. coccifera in Jebel Abederrahmane and on P. lentiscus in Sejnane. The tachinid observed in the two sites, on both host-plants in Jebel Abederrahmane and only on Q. coccifera in Sejnane. Overall mortality (parasitism and other factors) is higher in Jebel Abederrahmane (79.62%) than in Sejnane (20.37%). Parasitism rate reached 33% (206/623) in Jebel Abderrahmane and 39% (55/138) in Sejnane. It is also important to follow the dynamics of populations of parasitoids of larvae of O. trigotephras over the years and for the other stages of development of the insect.

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