Efficacy of the Entomopathogenic Fungus Metarhizium anisopliae var. acridum in Controlling Heteracris littoralis (Rambur, 1838). Using plant oil Carrier Substance Combined with Essential oils

Abstract

Using sunflower oil and essential oils (garlic, parsley, and basil), the study assessed the effectiveness of Metarhizium anisopliae var. acridum (isolate EV CH 077) against the grasshopper Heteracris littoralis, a major threat to agriculture in Egypt.  Ten treatments with different concentrations of essential oils (10%, 30%, and 50%) mixed with sunflower oil as a carrier were used in field experiments in the Baharia Oases throughout two summer seasons (2022 and 2023).  Analysis was done on synergistic effects, lethal time (LT₅₀ and LT₉₀), and mortality rates.

The results showed that, in comparison to other treatments, Metarhizium anisopliae plus 50% parsley oil (T6) produced 100% mortality by day 15 of the first season and day 12 of the second.  Garlic oil was less effective, but basil oil (50%) showed excellent efficacy as well (96.53% mortality).  The increased pathogenicity of fungal formulations with essential oils was demonstrated by the 86.11% death rate of sunflower oil alone (T0).  In treatments with essential oils, especially parsley (4.69 days in season 1; 5.14 days in season 2), LT₅₀ values were significantly lower, suggesting faster fungal action.  Significant changes between treatments were confirmed by statistical analysis (ANOVA, Tukey test, p < 0.05), with parsley oil demonstrating the strongest synergy.

The study highlights the potential of using essential oils produced from plants in conjunction with Metarhizium anisopliae as a sustainable substitute for chemical pesticides.  Particularly, parsley oil proved to be a very successful adjuvant, increasing fungal virulence and decreasing time-to-kill.  These results support integrated pest control plans by providing a sustainable way to reduce environmental and non-target hazards while reducing Heteracris littoralis infestations.