Meteorus gyrator (Thunberg) (Hymenoptera: Braconidae) In Egypt: Geographical Distribution and Mass-production

Abstract

Background: The larval internal parasitoids in the genus Meteorus attack certain lepidopterous larvae in different Egyptian fields. Two species, M. rubens and M. gyrator were the most abundant species reared from several lepidopterous larval species, which feed on different host plants in the two selected Governorates in Egypt throughout two successive years.
 Aim: This work presents a method specifically designed to improve the abundance and the parasitizing potential of M. gyrator in open fields to parasitize and develop on a broad range of noctuid’s pests by releasing considerable number of the parasitoid adults. Also it deals with some aspects of the basic biology of M. gyrator parasitizing Spodoptera littoralis and Autugrapha ni, as mass-rearing hosts.
 Methodology: 1- Population Dynamics
 Biweekly samples of lepidopterous larvae were collected from different host plants in the fields of Giza and Faiyum Governorates, for two successive years (November, 2017 to October, 2019). Collected larvae were confined individually under constant conditions until pupation or the emergence of the internal parasitoid’s larvae for pupation.
 2- Laboratory Rearing
 Cultures of some insect larvae, Heliothis armigera, Spodoptera exigua, Agrotis ipsilon, Sesamia cretica, S. littoralis and Autographa ni were reared in laboratory under constant conditions to act as hosts for mass-production of the parasitoid, M. gyrator.
 Results: Obtained results reveal that A. ipsilon was the main host of M. rubens, it was more abundant in both years and localities of the survey. Meteorus gyrator was recorded at fewer numbers; it was reared from S. littoralis, S. exigua, S. critica, Heliothis spp. and Autographa spp. The parasitism percentage by M. rubens averaged 23.10% at Giza. While in the case of M. gyrator it averaged 3.25%. In Faiyum, the corresponding figure averaged 12.96% parasitism for M. rubens; while it averaged 6.93%, for M. gyrator. To increase the efficacy of M. gyrator, mass production experiments were carried out, suggesting that Autographa ni was the most suitable for mass-rearing than S. littoralis.
 Conclusion: To increase the efficacy of M. gyrator as an endoparasitoid, its numbers in the field should be increased by releasing a considerable number of adults, to control lepidopterous larval pests.

Maximizing the Role of the Internal Larval Parasitoid, Meteorus gyrator (Thunberg) in the Open Field as a Biological Control Agent Considering the Effects of Climatic Changes

“…On the other view, it was observed that M.gyrator preferred warmer temperatures than M.rubens for its maximum activity. The obtained results were matched with that reported [14,15,19,20,22].…”

“…These results indicated the poor abundance of the 2 nd species (M.gyrator) compared to M.eubens, throughout all collected lepidopterous larvae. These findings were agreed and confermed by many authors [14,15,19,20]. On the other view, it was observed that M.gyrator preferred warmer temperatures than M.rubens for its maximum activity.…”

“…Collected larvae were confined individually under constant conditions (25±2°C & 65±5% RH) till pupation of the collected larvae or till the emergence of the fullgrown internal Meteorus spp. larvae for pupation outside the cadavers [14,15].…”

“…Our findings were in accordance with those reported by other authors in their investigations on some lepidopteran larvae that were collected from different vegetables & crops in diverse zones of Egyptian fields, where they stated that the solitary parasitoid was common on S.littoralis, S.exigua, and Autographa spp. [14,15,19,20,22]. Because of the poor rate of M.gyrator abundance, and its wide parasitism range, mass rearing of adults was a solution for overcoming the shortage of its efficiency as an internal larval parasitoid.…”

“…Our survey in Egypt revealed that there are two active species, Meteorus rubens (the gregarious larval internal parasitoid; its recorded abundant periods lasted from February to May) and Meteorus gyrator (the solitary larval internal one; its abundant periods started from May to August) [14,15]. M.gyrator was recorded throughout other researches which was directed mainly towards some economic pests of lepidopterous insects in Egypt, such as Autographa spp., Heliothis armigera Hb., Sesamia cretica, Spodoptera littoralis Boisd., and S. exigua Hb., in different fields of vegetables, clover, and maize [16][17][18][19][20].…”