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

Background: Members of Braconidae, i.e., Meteorus spp. assault certain lepidopterous larvae in Egyptian fields. The recorded species M.rubens (gregarious) and M.gyrator (solitary) were the most species reared from some lepidopterous larvae attacking various host plants in two chosen Governorates in Egypt through two experimental years. This work aims to increase the parasitizing efficiency of M.gyrator in fields by releasing an impressive number of parasitoid adults.

Methods:

Samples of lepidopteran larvae were picked up from the prevailing plants in fields of El-Ghaebia and El-Sharkia Governorates, for two successive years (2020 to 2021). The prevailing plants are: clover, cabbage, okra, tomato, maize, jew's mallow, bean, soybean, cotton, pea, and lettuce. Collected larvae were reared under optimal conditions until their pupation or in anticipation of the migration of the full-grown endoparasitoid's larvae for pupation.

Parasitoid’s production: Species of some lepidopterous larvae were reared in the NRC laboratory for large-scale manufacturing of the parasitoid Meteorus gyrator.

Results: Acquired results uncover that Agrotis ipsilon was the primary noctuid host larvae of M. rubens during its abundant periods (February-May). While in case of M.gyrator it was recorded in fewer numbers (at its abundant periods, May-August); which was raised from other lepidopteran larvae.

The M. rubens parasitism percentage reached 26.50 and 21.79% at El-Gharbia Governorate through the two experimental years, respectively; whereas in the case of M. gyrator it was 2.25% in the 2nd experimental year only. In El-Sharkia, M. rubens parasitism percentage was 18.60 and 28.60%, respectively throughout the two experimental years; while it was 10.00% for M. gyrator in the first year only.

Conclusion: To boost the productivity of this solitary internal parasitoid as a bio-control agent, it is mandatory to increase its adults population in any field.