Reproductive toxicity and histopathological changes induced by lambda-cyhalothrin in male mice.

Lambda-cyhalothrin (LCT) is a widely used broad-spectrum pyrethroid insecticide. Oral LCT administration to adult male mice at 3 doses (0.2, 0.4, and 0.8 mg/kg/day) for 6 weeks caused a significant reduction in the weight of the seminal vesicles. The epididymal sperm count was lower in mice that received at the highest dose than in control mice. However, the proportions of live and motile spermatozoa were reduced at both the medium and the high doses compared with control mice. All doses induced an increase in the number of morphologically abnormal spermatozoa. Histopathological observations of the testes, liver, kidneys, and spleen showed dose-related degenerative damage in LCT-treated mice. The results indicate that LCT has reproductive toxicity, hepatotoxicity, nephrotoxicity, and splenotoxicity in male mice at the tested doses. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 750-762, 2014.

First Report on Banana Weevil, Cosmopolites sordidus (Germar 1823) (Coleoptera: Curculionidae), an Exotic Economically Important Pest from Saudi Arabia.

We report the first record of the occurrence of the banana weevil, Cosmopolites sordidus (Germar, 1823) (Coleoptera: Curculionidae), an economically important pest of bananas (Musa spp.), from Fifa Mountains in Saudi Arabia. Moreover, we recorded the first observation of damage caused to bananas by C. sordidus in a banana farm in Jazan Province, southwestern Saudi Arabia, in March 2022. Molecular characterization using DNA sequences of the mitochondrial COI gene confirmed the morphological identification of C. sordidus. This discovery is considered a warning notice to prevent the potential establishment and spread of this dangerous pest in the banana cultivation regions in Saudi Arabia. Therefore, it is recommended that detection and monitoring of banana weevil should be undertaken in Saudi banana farms in order to restrict the dissemination of this weevil to other banana cultivation areas.

Single and Combined Mutations of Acetylcholinesterase Gene Giving Resistance to Pirimiphos-Methyl in Musca domestica Slaughterhouse Populations.

The house fly Musca domestica L. (Diptera: Muscidae) is a worldwide medical and veterinary pest, causing great economic losses. Organophosphate insecticides have been widely used to control house fly populations. The main objectives of the present study were to evaluate the resistance levels of M. domestica slaughterhouse populations, collected from Riyadh, Jeddah, and Taif, against the organophosphate insecticide pirimiphos-methyl and investigate the genetic mutations of the Ace gene associated with pirimiphos-methyl resistance. The obtained data showed that there were significant differences among pirimiphos-methyl LC50 values of the studied populations, where the highest LC50 was recorded for the Riyadh population (8.44 mM), followed by Jeddah and Taif populations (2.45 mM and 1.63 mM, respectively). Seven nonsynonymous SNPs were detected in the studied house flies. The Ile239Val and Glu243Lys mutations are reported for the first time, whereas Val260Leu, Ala316Ser, Gly342Ala, Gly342Val, and Phe407Tyr were previously reported in M. domestica field populations from other countries. Considering three mutations associated with insecticide resistance, at amino acid positions 260, 342, and 407 of acetylcholinesterase polypeptide, 17 combinations were recovered in this study. Three out of these seventeen combinations were frequently found both worldwide and in the three Saudi house fly field populations, as well as their pirimiphos-methyl-surviving flies. Overall, the single and combined Ace mutations are apparently associated with pirimiphos-methyl resistance, and the obtained data can be useful in managing house fly field populations in Saudi Arabia.

Organophosphate Insecticides Resistance in Field Populations of House Flies, Musca domestica L.: Levels of Resistance and Acetylcholinesterase Activity.

The house fly, Musca domestica L., is an important medical and veterinary pest associated with humans and livestock. Management of house flies has relied extensively on chemical control. In this study, we report on the resistance of house fly field-collected populations to diazinon and fenitrothion OP insecticides in Riyadh, Saudi Arabia. The diazinon and fenitrothion median lethal dose (LD50) values against adult female M. domestica field-collected populations were significantly higher than those of the laboratory (LAB) strain. Different levels of resistance were detected in all field-collected populations toward the two OP insecticides. The resistance ratios for diazinon ranged from 62.47 to 309.78, while there were 53.08 to 261.24 for fenitrothion in the eight field-collected populations. The specific activity of acetylcholinesterase (AChE) in all field populations was significantly (p < 0.05) higher than that in the LAB strain. In vitro diazinon and fenitrothion median inhibitory concentration (IC50) values of LAB strain AChE activity were significantly (p < 0.05) lower than those for field-collected populations. This study found high levels of resistance in the house fly field-collected populations to diazinon and fenitrothion. Replacing these two insecticides and any other OPs with novel ones that have different modes of action is an urgent need in the insect-vector control programs in Riyadh, Saudi Arabia. An altered AChE enzyme of M. domestica field populations might be partially responsible for the developed resistance. Monitoring of insecticide resistance development in M. domestica populations and a better understanding of its mechanisms are needed to design operative management strategies for controlling the house flies.

Effects of space spray application methods on fenitrothion efficacy and development of resistance in Culex pipiens.

Efficacy of fenitrothion as thermal fogging (TF) or ultra-low volume (ULV) applications against 6 successive generations of caged adult Culex pipiens and subsequent development of resistance in both adults and larvae were investigated in this study. In addition, larval acetylcholinesterase (AChE) activity was measured in each generation. Results indicated that the ULV application method was significantly more effective (P < 0.05) than TF against the adults in all treated generations. Selection pressure of TF and ULV applications on the adults after 5 generations resulted in larval resistance by ratios of 30.92- and 28.18-fold, respectively. A gradual decrease in the larval AChE activity was observed with increasing resistance as generations progressed. The AChE activity of susceptible larvae was higher than that of the F5 resistant generation in TF and ULV treatments by 6- and 8-fold, respectively. The results indicated that both the biological efficacy of fenitrothion and the rapidity of resistance development were affected by the application methods.

Levels of heavy metals in a multifloral Saudi honey.

The presence of chemical pollutants, especially heavy metals, affects the quality of honey. The objective of this study was to determine the levels of eight heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) in honey samples from Al-Baha region in Saudi Arabia, using inductively coupled plasma with optical emission spectroscopy (ICP-OES). The highest concentration was found for Zn (1707.93 µg kg-1), while the lowest was found for Co (3.04 µg kg-1). Cluster analysis and principal component analysis showed that two groups are recognized indicating two different metal sources. The first group includes only Zn and the second group includes the rest of the metals. In view of the recommended and established heavy metal intakes for humans, consumption of Saudi honey from Al-Baha should not be deemed a matter of concern for human health.

Molluscicidal activity of cardiac glycosides isolated from Adenium obesum.

BACKGROUND: Terrestrial mollusks are one of most important agricultural pests worldwide. Natural phytochemicals have an extended history as a source of pesticides. This study was planned to isolate molluscicidal active compounds from the stems of Adenium obesum. RESULTS: The benzene-soluble fraction of the hydroethanolic extract displayed the most potent molluscicidal activity against Monacha obstructa among different solvent fractions with a median lethal dose (LD50 ) of 4.91 µg g-1 body weight (bw). The bioactivity-guided chemical exploration of the benzene-soluble fraction led to the isolation of two known cardiac glycosides, cerberin and neriifolin which showed significant molluscicidal activity with LD50 values of 5.39 and 4.3 µg g-1 bw, respectively. CONCLUSION: Isolation of the cardiac glycoside neriifolin from A. obesum and the molluscicidal activity of cerberin and neriifolin against terrestrial snails are reported for the first time. © 2019 Society of Chemical Industry.

Cytotoxic and genotoxic effects of abamectin, chlorfenapyr, and imidacloprid on CHOK1 cells.

The cytotoxicity and genotoxicity of abamectin, chlorfenapyr, and imidacloprid have been evaluated on the Chinese hamster ovary (CHOK1) cells. Neutral red incorporation (NRI), total cellular protein content (TCP), and methyl tetrazolium (MTT) assays were followed to estimate the mid-point cytotoxicity values, NRI50, TCP50, and MTT50, respectively. The effects of the sublethal concentration (NRI25) on glutathione S-transferase (GST), glutathione reductase (GRD), glutathione peroxidase (GPX), and total glutathione content have been evaluated in the presence and absence of reduced glutathione (GSH), vitamin C, and vitamin E. The genotoxicity was evaluated using chromosomal aberrations (CA), micronucleus (MN) formation, and DNA fragmentation techniques in the presence and absence of the metabolic activation system, S9 mix. Abamectin was the most cytotoxic pesticide followed by chlorfenapyr, while imidacloprid was the least cytotoxic one. The glutathione redox cycle components were altered by the tested pesticides in the absence and presence of the tested antioxidants. The results of genotoxicity indicate that abamectin, chlorfenapyr, and imidacloprid have potential genotoxic effects on CHOK1 cells under the experimental conditions.

Insecticide resistance of Culex pipiens (L.) populations (Diptera: Culicidae) from Riyadh city, Saudi Arabia: Status and overcome.

Three field populations of Cx. pipiens (L.) mosquitoes were collected from three different localities in Riyadh city. They were tested for developing resistance against commonly used insecticides to control mosquitoes in Riyadh. Two populations from Wadi Namar (WN1 and WN2) were highly resistant to deltamethrin (187.1- and 161.4-folds respectively). The field population from AL-Wadi district (AL-W) showed low resistance to lambda-cyhalothrin (3.8-folds) and moderate resistance to beta-cyfluthrin and bifenthrin (14- and 38.4-folds respectively). No resistance to fenitrothion was observed in WN1 population. Fenitrothion concentrations required to inhibit 50% of Acetylcholinesterase (AChE) activity in both WN1 population and the laboratory susceptible strain (S-LAB) were 0.073 and 0.078 ppm respectively. Piperonyl butoxide suppressed resistance to pyrethroid insecticides (>90%) in field populations indicating that oxidases and/or esterases play an important role in the reduction of pyrethroids toxicity. These results should be considered in the current mosquitoes control programs in Riyadh.