Evaluation of the Impact of Five Bio-insecticides of Plant Origin and a Chemical Insecticide on the Survival of Imagos of the Parasitoid Aphidius colemani under Laboratory Conditions

Aims: The present study aims to evaluate the control pests without the harms of chemical pesticides as well as ensure the safety of bio-insecticides of plant origin vis a vis females of the parasitoid Aphidius colemani, important auxiliary in biological control.

Study Design: Experimental device was in a complete random block with three replications.

Place and Duration of Study: Laboratory of Bio-insecticidal Entomology and Laboratory of weed science of Regional Center of Agricultural Research, Kenitra, INRA-Morocco and Laboratory of Nutrition, Health and Environment. Biodiversity and agro resources team Ibn Tofail University, Faculty of Sciences Kenitra Morocco. The experiment was conducted between the fall of 2018 (from September to December 2018) and the winter of 2019 (January-February 2019).

Methodology: To meet the objective of this work, four endemic plants were collected from the Gharb region of Morocco; these are the leaves of Nerium oleander that are available all year, the roots of Mandragora autumnalis, the fruits of Capsicum frutescens, and those of Melia azedarach these organs are well developed with complete maturity during the fall and winter. The fruits of Melia azedarach have been separated into seeds and pulps. Five concentrations of each aqueous extract were prepared (2; 5; 10; 15 and 20 g / 20 ml). In addition to control without any treatment (blanc) and a chemical insecticide (deltamethrin). All concentrations were administered by contact to females of Aphidius colemani.

Results: Comparing the bio-insecticides tested, the aqueous extract of the seed of Melia azedarach showed an insecticidal action that was the fastest and the most toxic. Thus, following exposure of 20 g/20 ml, the observation after 4 hours showed a minimum mortality rate of 3% and a maximum mortality rate of 50%, 96 hours after. This extract was followed by the aqueous extract of the leaves of Nerium oleander that showed a maximum mortality rate of 43%. However, their harmfulness remains much lower than that of deltamethrin. In addition, the aqueous extract of the roots of Mandragora autumnalis has proved to be safe for females of Aphidius colemani. On the other hand, the aqueous extract of the fruits of Capsicum frutescens and that of the pulp of Melia azedarach are moderately toxic.

Conclusion: By way of conclusion, the aqueous extract of the roots of Mandragora autumnalis could be used as an insecticide in parallel with the release of the parasitoid Aphidius colemani, in a biological control.