Monarda fistulosa hydrolate as antimicrobial agent in artificial media for the in vitro rearing of the tachinid parasitoid Exorista larvarum

Abstract

Exorista larvarum (L.) (Diptera: Tachinidae), a larval parasitoid of Lepidoptera, can be reared from egg to fecund adult on artificial media composed of crude components. The standard in vitro culture is performed in 24-well plastic rearing plates. Exorista larvarum eggs, removed from superparasitized larvae of Galleria mellonella (L.) (Lepidoptera: Pyralidae), are individually placed in the wells, each containing a cotton swab soaked in liquid medium. The plates are then sealed until parasitoid puparium formation. To avoid contamination by microorganisms, the artificial medium is routinely supplemented with 0.01% solution of gentamicin. Experiments were carried out to assess whether this broadspectrum antibiotic may be replaced with hydrolate of Monarda fistulosa L. (Lamiaceae), which was selected due to its high in vitro activity against pathogenic microorganisms for humans and plants. The hydrolate was either supplemented to the artificial medium (0.5% wt/wt) (first experiment) or placed in an empty well (200 ll) of the rearing plate, to be supplied as saturated air due to evaporation (second experiment). In both experiments, a standard medium with gentamicin and an antimicrobialfree medium were maintained as positive and negative controls, respectively. In the first experiment, in the hydrolate-supplemented medium fewer E. larvarum completed egg-to-adult development than in the standard medium, but significantly more parasitoids developed from egg to adult compared to the antimicrobial-free medium. No significant difference was found between the numbers of eggs laid by the females obtained from the standard medium vs. those from the hydrolate-supplemented medium. In the second experiment, the hydrolate-saturated air significantly decreased E. larvarum egg hatching, puparium formation, and female fecundity compared to the standard medium. In perspective, M. fistulosa hydrolate supplemented to the artificial media for E. larvarum may be considered as a promising candidate to replace the gentamicin solution, as suggested also by the microbiological analyses of the media, performed at various growth stages of the parasitoid in a separate trial. Conversely, the hydrolate-saturated air treatment was deemed unsuitable.

A Review on Pharmacological Activity of Monarda fistulosa L.

“…Numerous European countries have been cultivating M. fistulosa as an aromatic plant. Studies have shown that M. fistulosa is rich in biologically active substances, making it a great source of EOs (Dindo et al, 2020). Furthermore, studies have proven that the EOs and hydrolates from M. fistulosa exhibit high activity against pathogenic microorganisms and can be used in humans and plants (Dindo et al, 2020).…”

“…Studies have shown that M. fistulosa is rich in biologically active substances, making it a great source of EOs (Dindo et al, 2020). Furthermore, studies have proven that the EOs and hydrolates from M. fistulosa exhibit high activity against pathogenic microorganisms and can be used in humans and plants (Dindo et al, 2020). Some of the major constituents found in M. fistulosa, such as carvacrol, γ-terpinene, geraniol, rosmarinic acid, and thymol, as well as the presence of thymol and carvacrol in the EOs of M. fistulosa, enable the extract to pose antibacterial and antihelmintic properties (Mattarelli et al, 2017).…”

“…Some of the major constituents found in M. fistulosa, such as carvacrol, γ-terpinene, geraniol, rosmarinic acid, and thymol, as well as the presence of thymol and carvacrol in the EOs of M. fistulosa, enable the extract to pose antibacterial and antihelmintic properties (Mattarelli et al, 2017). According to Dindo et al (2020), thymol is the bioactive compound that exhibited one of the strongest antimicrobial activities when incorporated with 0.5% (w/w) of M. fistulosa hydrolate containing 0.143 mM (0.0022%) of thymol into an artificial medium placed with E. larvarum eggs for in vitro analysis.…”

Monarda didyma Hydrolate Affects the Survival and the Behaviour of Drosophila suzukii

“…For this reason, the major components of an EO may not be the same present in the corresponding HY. However, several HYs possess antimicrobial and antifungal activity [ 33 , 35 , 36 , 37 , 38 , 39 ], but only a few studies have investigated their insecticidal action. Petrakis and colleagues [ 40 ] examined the possible use of HYs from Origanum majorana L., Mentha pulegium L., and Melissa officinalis L. against Myzus persicae Sulzer, showing that they altered the insect locomotion and fitness.…”

Entomophagous insects – an introduction

“…By examining several aspects of parasitoid oviposition behavior and reproductive success, this study shows that C. cephalonica is suitable as an alternative host for mass rearing of S. brevicornis. Dindo et al (2021) then investigated the efficacy of Monarda fistulosa L. (Lamiaceae) hydrolate as antimicrobial agent in artificial media for in vitro rearing of the parasitoid Exorista larvarum (L.) (Diptera: Tachinidae), as an alternative to the use of antibiotics (gentamicin). Although effective in controlling bacterial load, the M. fistulosa hydrolate supplemented to the artificial media significantly reduced E. larvarum development from the egg to the adult stage compared to gentamicin-supplemented medium, but not the number of eggs laid by the emerging females.…”