Insecticidal Activity and Physicochemical Characterization of Nanoparticles from Foliar Extract of Capsicum chinense

This work was carried out to evaluate the insecticidal effect of mono,bi and trimetallic nanoparticles(NPs)from leaf extract of habanero pepper(Capsicum chinense Jacq.)on the red flour beetle(Tribolium castaneum herbst.)and cotton mealybug(Phenacoccus solenopsis Tinsley).The results showed that Cu NPs,Cu/Mn NPs and Zn/Cu NPs had high insecticidal effect against T.castaneum(63%-80% mortality after 96 h).The Cu NPs and Zn/Cu NPs showed also insecticidal effect against P.solenopsis,but to a lesser extent(20%–28% after 96 h).With regards to the physicochemical characterization,Cu NPs had a zeta potential of 21.1 mV,whereas Cu/Mn NPs and Zn/Cu NPs exhibited zeta potentials of 200 mV.The polydispersity index(PDI)values for Cu NPs,Cu/Mn NPs,and Zn/Cu NPs were 10.1,29.16,and 14.34,respectively.The TF-IR spectra of the NPs varied from 600 to 4000 cm−1.The EDX weight percentages showed the presence of Cu(0.29%–2.4%),Mn(1.4%),and Zn(2.6%)in Cu/Mn NPs and Zn/Cu NPs,respectively.

Exposition of Pecan Black Aphid(Melanocallis caryaefoliae)to Creseote Bush(Larrea tridentata)Extracts

Creseote bush-based (Larrea tridentata Cov.) botanical insecticides have not been evaluated on pecan black aphid (Melanocallis caryaefoliae D.), the purpose of this research was to test the insecticide and/or repellent effect of the creseote-bush raw extracts on this insect. Ethyl acetate, methanol and water as solvents, the stem and leaf organs were tested at concentrations of 0.5%, 1%, and 2%, as well as their witnesses and the interactions of each. Extract application was made by immersion during 10 s and the incubation was made in a wet chamber, making observations at 24, 48 and 72 hours after the treatment was applied. Mortality was evaluated by touching the aphid and seeing it did not move, while for repellence the insects found outside of the leaf were taken into account. A higher mortality effect was observed at a 1% concentration for the three solvents on the leaf extracts, being the methanol one the most efficient, on the other hand the stem extracts had the same behavior, presenting the higher mortality in the ethyl acetate extracts at 0.5% and 2% both at 72 hours. On the other hand the higher repellent effect presented at 24 hours in stem extracts, with a variation in the leaf extracts.

Role of DSC1 in Drosophila melanogaster synaptic activities in response to haedoxan A

Drosophila sodium channel 1 (DSC1) encodes a voltage-gated divalent cation channel that mediates neuronal excitability in insects. Previous research revealed that DSC1 knockout Drosophila melanogaster conferred different susceptibility to insecticides, which indicated the vital regulation role of DSC1 under insecticide stress. Haedoxan A (HA) is a lignan compound isolated from Phryma leptostachya, and we found that HA has excellent insecticidal activity and is worthy of further study as a botanical insecticide. Herein, we performed bioassay and electrophysiological experiments to test the biological and neural changes in the larval Drosophila with/without DSC1 knockout in response to HA. Bioassay results showed that knockout of DSC1 reduced the sensitivity to HA in both w1118 (a common wild-type strain in the laboratory) and parats1 (a pyrethroid-resistant strain) larvae. Except for parats1/DSC1−/−, electrophysiology results implicated that HA delayed the decay rate and increased the frequency of miniature excitatory junctional potentials of Drosophila from w1118, parats1, and DSC1−/− strains. Moreover, the neuromuscular synapse excitatory activities of parats1/DSC1−/− larvae were more sensitive to HA than DSC1−/− larvae, which further confirmed the functional contribution of DSC1 to neuronal excitability. Collectively, these results indicated that the DSC1 channel not only regulated the insecticidal activity of HA, but also maintained the stability of neural circuits through functional interaction with voltage-gated sodium channels. Therefore, our study provides useful information for elucidating the regulatory mechanism of DSC1 in the neural system of insects involving the action of HA derived from P. leptostachya.

Negative cross-resistance of a pyrethroid-resistant Drosophila mutant to Phryma leptostachya-derived haedoxan A

Voltage-gated sodium channels are the primary target of pyrethroid insecticides.Mutations in sodium channel confer knockdown resistance(kdr)to pyrethroids in various arthropod pests.Haedoxan A(HA)is the major insecticidal component from Phryma leptostachya.It has been shown that HA alters electrical responses at the Drosophila neuromuscular junction and modifies the gating properties of cockroach sodium channels expressed in Xenopus oocytes.However,whether sodium channel mutations that confer pyrethroid resistance also affect the action of HA is unknown.In this study,we conducted bioassays using HA and permethrin in two Drosophila melanogaster strains:w^(1118),an insecticide-susceptible strain,and para^(tsl),a pyrethroid-resistant strain due to a I265N mutation in the sodium channel,and identified a new case of negative cross-resistance(NCR)between permethrin and HA.Both para^(tsl) larvae and adults were more resistant to permethrin,as expected.However,both para^(tsl) larvae and adults were more sensitive to HA compared to w^(1118).We confirmed that the I265N mutation reduced the sensitivity to permethrin of a Drosophila sodium channel variant,DmNa_(v)22,expressed in Xenopus oocytes.Interestingly,the I265N mutation also abolished the effect of HA on sodium channels.Further characterization showed that I265 on the sodium channels is critical for the action of both pyrethroids and HA on sodium channels,pointing to an overlapping mode of action between pyrethroids and HA on the sodium channel.Overall,our results suggest an I265N-independnt mechanism(s)in para^(tsl) flies that is responsible for the NCR between permethrin and HA at the whole insect level.

Toxicological and histopathological effects of Dennettia tripetala seed used as grain protectant,food,and medicine

The study revealed the safety of Dennettia tripetala seed on man and the environment.Adult male rats weighing 0.158-0.168 kg housed in standard cages with free access to food and water were used for the experiments.The median lethal dose(LD50)was estimated using revised up and down procedure.The LD50 for D.tripetala seed extract was 5785 mg/kg and this evoked paralysis in rats for 4 days coupled with discharge from the eyes and eventual death.The least weight gain by the animals administered 75%seed powder of D.tripetala(4338.75 mg/kg)was an index of high powder concentration,whereas the weight loss experienced by group V animals is strongly attributed to chemical assault by permethrin designated as a standard insecticide.The high values of alanine aminotransferase(ALT),aspartate aminotransferase(AST),and urea in the groups administered 75%permethrin powder(4338.75 mg/kg)and 75%D.tripetala seed powder is an index of liver and kidney injury and dysfunction.The presence of normal serum levels of ALT,AST,alkaline phosphatase,and creatinine;normal liver and kidney structures;and normal weight gains in the animal groups fed basal diet(control)and basal diet plus 25%D.tripetala is a strong indication that 25%D.tripetala seed powder(1446.25 mg/kg)supplementation is not toxic to the liver and kidney and therefore supports normal organ functions.The LD50 recorded strongly indicates that D.tripetala has a moderately high safety margin.Supplementation of less than 50%(2892.5 mg/kg)is recommended in the safe use of the plant material as grain protectant,food,and medicine.The botanical insecticide,D.tripetala,is safer than the conventional synthetic insecticide,permethrin,on account of the latter showing evidence of kidney damage.