Lethality of Sesquiterpenes Reprogramming Red Palm Weevil Detoxification Mechanism for Natural Novel Biopesticide Development

Abstract

Natural biopesticide development for invasive populations of red palm weevils is mainly responsible for the destruction of date palms and demands an extensive screening program of plant secondary metabolites. In the current study, the pesticidal potential of sesquiterpenes (C15 H24), an important class of plant secondary metabolites primarily composed of three isoprene units, was evaluated by laboratory toxicity, feeding performance bioassays, and host detoxification gene expression patterns. Dose-mortality response bioassays performed against mid-aged eighth-instar red palm weevil larvae revealed dose-dependent mortality. Only three sesquiterpenes, including Farnesol (LD50 = 6559 ppm) and Farnesyl acetate (LD50 = 7867 ppm), are considered to have significant toxicity, with Picrotoxin (LD50 = 317 ppm) being the most toxic. Furthermore, highly toxic sesquiterpene (Picrotoxin) established in the current study tremendously reduced the feeding performance indices, including the efficacy of conversion of digested food (ECD) (81.74%) and the efficacy of conversion of ingested food (ECI) (73.62%). The least toxic sesquiterpenes, including β-Caryophyllene, (+)-Cedrol, Nerolidol, (+)-Nootkatone, and Parthenolide, observed in the current study failed to impart significant reductions of ECI and ECD indices. Lethality of the least toxic sesquiterpenes was overcome by greatly inducing gene expressions of Glutathione S transferase (GST) and Cytochrome P450. These encouraging results enabled us to suggest Picrotoxin as a promising biopesticide for the control of red palm weevil infestations.

Development-Disrupting Chitin Synthesis Inhibitor, Novaluron, Reprogramming the Chitin Degradation Mechanism of Red Palm Weevils

“…Dietary utilization experiments on the ninth-instar red palm weevil larvae revealed tremendous reduction in ECI (74.27%) and ECD (82.38%) indexes at all tested doses of novaluron compared with the control treatment. Previous studies corroborated our findings, suggesting that the potent treatments whether plant extracts [7], conidial suspensions of entomopathogenic fungal isolates [15,37], plant secondary metabolites [8,9,10], or pesticides [21], tremendously reduced the ECD and ECI indexes. These findings enabled us to suggest that inhibition in growth indices among exposed red palm weevils arise mainly due to their depleting energy reserves.…”

“…The exposed red palm weevil larvae spend most of their energy reserved on their detoxification mechanism coping with toxins. These exposed energy-deficient red lam weevils could not withstand toxins, ultimately became sluggish, growth retarded, and died [9]. Our results are also in agreement with other pest species showing disturbed growth and development patterns in case of Helicoverpa armigera (Hubner) against limonoids [40], Ocinara varians Walker against conidial suspensions [39], and Anagasta kuehniella against Croton urucurana extracts [41].…”

“…Larval growth and development that is mainly assessed on the basis of feeding indices including approximate digestibility (AD), efficacy of conversion of digested (ECD), and ingested food (ECI) are important growth parameters [9,15,37]. In the present study, disturbed larval growth and development patterns were recorded from feeding indices calculated from diet incorporated laboratory bioassays.…”

“…Mainly larval stage is responsible for the destruction of palms. Therefore, tremendous research on the evaluation of host plant resistance [3], pheromone traps in controlling RPW [4,5], sterile insect technique [6], plant secondary metabolites [7,8,9,10], entomopathogenic nematodes [11], entomopathogenic fungi [12,13,14,15], have been done to control the invasive populations of red palm weevils worldwide. Among them, the use of different groups of insecticides as soil treatment, tree fumigation, trunk injection, wound dressing, and crown drenching of infested palms remained the focus of most of the research investigations [16,17,18,19,20].…”

Potential Synergy between Spores of Metarhizium anisopliae and Plant Secondary Metabolite, 1-Chlorooctadecane for Effective Natural Acaricide Development

“…Fungal infection evades the host defense mechanism by triggering complex biochemical interactions in the form of series of events through cuticle adhesion, penetration, proliferation, and toxin production, which ultimately lead to the host mortality [29,[31][32][33]. On the other hand, plant secondary metabolites are known antagonists that act by interfering with the signaling of the nervous and cellular systems to overcome the target host defense mechanism [34][35][36][37][38]. Therefore, the combined application is considered as a promising approach due to the differences in their mechanism of actions.…”