Larvicidal activities of chinaberry,neem and Bacillus thuringiensis israelensis(Bti) to an insecticide resistant population of Anopheles arabiensis from Tolay,Southwest Ethiopia

Objective:To elucidate the larvicidal potency of neem, chinaberry and Bacillus thuringiensis israelensis(Bti) to larvae of Anopheles arabiensis under semi-field condition and adult susceptibility/resistance to the conventionally used insecticides in Tolay,Southwestern Ethiopia.Methods: Wild collected 3rd and 4th stage larvae were exposed to neem, and chinaberry seed powder dissolved in water and Bti in artificial containers at three treatment levels:0.2, 0.1 and 0.05 g/m^2 and controls were free of treatments. Larval and pupal mortalities were monitored daily and residual activities were determined. The experiments were replicated three times. The World Health Organization tube test for all classes of insecticides was conducted on adult Anopheles arabiensis reared from field collected larvae and pupae. Data were analyzed using STATA software version 11.Results: In the first application, neem powder caused 88.9%, 87.9% and 79.4% larval and pupal mortality at 0.2, 0.1 and 0.05 g/m^2 after 4.3, 6.0 and 5.7 days, respectively. The corresponding killing effect of chinaberry was 80.3%, 62.1% and 30.3% after 7.0, 7.7 and 8.3days respectively. Bti at all treatments killed 100% after 24 h except 2.7 days for 0.05 g/m^2.Adult mosquitoes were susceptible only for fenitrothion and pirimiphos-methyl with 100%mortality while resistant to deltamethrin, alpha-cypermethrin, etofenprox and dichlorodiphenyl-tricgloroethane with only 9.0%, 3.0%, 5.1% and 2.0% mortalities respectively.Conclusions: Neem, chinaberry and Bti showed potent larvicidal and pupicidal activities. However, in the area, high level of mosquito resistance to pyrethroids and dichlorodiphenyl-tricgloroethane was seen which will pose serious challenge to vector control in the future. Therefore, using integrated approach including these botanical larvicides is warranted to manage insecticide resistance.

Biocontrol potential of entomopathogenic nematode,Heterorhabditis indica against pink bollworm,Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae)

Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and cost-effective control methods.This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes(EPNs),Heterorhabditis indica,namely CICR-HI-CL and CICR-HI-MN,against PBW larvae and pupae under in-vitro conditions.Results The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd,3rd,and 4thinstar larvae,with median lethal dose(LD50)values of 5.45,4.45,and 4.60 infective juveniles(IJs)per larva,respectively.In case of pupal bioassay,both EPN strains demonstrated greater virulence when applied directly(LD50values:29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN,respectively)compared to soil application(147.84 and 272.38 IJs per pupa).Both EPN strains successfully penetrated and reproduced on 4thinstar larvae,resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.Conclusion The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H.indica(CICR-HI-CL and CICR-HI-MN)against PBW,a dreaded pest of cotton.Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply,sustain and perpetuate on larval and pupal stages of PBW.The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate.The soil-dwelling life stages viz.,last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H.indica for sustainable management of PBW in the cotton ecosystem.However,before taking these EPN strains to field for managing PBW,detailed studies investigating their biocontrol potential against PBW under field conditions are needed.

Assessing the Impact of Storage Temperature on the Stability and Biocidal Activity of Essential oils Formulated, Case Tribolium Castaneum （herbst）. （insecta, tenebrionidae）

In this paper, authors describe how to carry out a research assessing the impact of storage temperature on the stability and biocidal activity of formulated essential oils. Cereals, like other stored food, currently experience serious health problems of storage. The offending agents are primary pests such as Sitophilusoryzae and secondary pests including Tribolium. This study focused on the evaluation of the biocidal effect on the essential oils of thyme and citrus, against red flour beetle adults （Triboliumcastaneum） under different temperature regimes. The results showed that different molecules produced a delayed effect （12 h-14 h-16 h-I 8 h） on the populations of Triboliumcastaneum at the storage temperature of 20 ~C. The same results showed an early striking effect of thymol and carvacrol on Triboliumcastaneum compared to limonene. The toxicity of thymol and carvacrol was much more active than limonene at 12 h, which was very remarkable as limonene expressed its toxicity from 14 h with a deadly effect. When temperatures are under 20 ℃ and 25℃, thymol showed a greater degree of efficiency followed by carvacrol and limonene which had lower efficiency. However, at 28℃, carvacrol expressed a very significant biocidal effect compared to the other two formulations, thymol and limonene.

Field Durability of Yorkool^(█) LN Nets in the Benin Republic

Context: Recent publications on WHO recommended methods for estimating the survival of LLINs are good guidelines for assessing the performance of long-lasting insecticidal nets (LLINs). Thus, this field trial study was undertaken to evaluate the durability of the Yorkool? LN mosquito net distributed during the 2017 campaign in Benin. Methods: The monitoring of Yorkool? LN nets was carried out in two districts (Djougou III and Barienou) in Djougou, department of Donga, northern Benin from October 2017 to March 2019. A representative sample of 250 households that had received the Yorkool? LN polyester LLINs during the 2017 campaign was selected in the rural and urban areas of each district and monitored for 6, 12 and 18 months. An evaluation of the survival of Yorkool? LN nets was conducted based on the rate of loss and physical condition of the surviving nets as measured by the proportional hole index (pHI). Finally, the chemical efficacy of these LLINs during each period was determined using the WHO cone tests. Results: Survival of Yorkool? LN nets was similar in both rural and urban areas, although there was a difference in survival between the 6-month (95.3%), 12-month (89.7%), and 18-month follow-up periods (74.4%). A difference in survival was also observed between the NetCalc model (84%) compared to the Yorkool? LN nets of this study (74.4%). The attrition rate was 29.6% for LLINs at 18 months. Surprisingly, the physical integrity of the LLINs was minimally affected in the municipality. Indeed, the proportion of mosquito nets in good condition without a hole was 51.8% compared to 56.8% with a hole after 18 months. Only 7.8% of the LLINs in the two districts were damaged compared to 2.6% which needed to be replaced. The washing frequency, location of the LLINs and the frequency of use are some factors contributing to the appearance of the holes in LLINs. The bio-efficacy results of LLINs based on the cone test were good with mortality rates of 74%, 66%, 72% and 58% respectively after baseline, 6, 12 and 18 months of use. Conclusions: The observed differences in the survival of Yorkool? LN nets are due to community living conditions and movements and not to the equipment used to manufacture LLINs. However, the estimated median survival has shown that Yorkool? LN nets would have an average lifespan of 2 years 8 months despite their fairly good physical condition. These results may be useful to the National Malaria Control Program (NMCP) during the period of replacement of these nets on the field.

Unmanned aerial vehicle (UAV)-assisted pesticide application for pest and disease prevention and control in rice

Unmanned Aerial Vehicles (UAVs) have emerged as innovative tools in agriculture, revolutionizing crop protection practices and the use of pesticide combinations to aid the management of insect pests and diseases in a single application. This research delves into assessing the efficacy of drone-based pesticide spraying utilizing combinations of pesticides to combat insect pests and diseases in rice cultivation. In kharif 2022, the physically compatible combination of insecticides (chlorantraniliprole 18.5% SC and tetraniliprole 200 SC) with fungicides (picoxystrobin 7.5%+tricyclazole 22.5% SC and tebuconazole 50%+trifloxystrobin 25% WG) were administered via drones and compared with conventional Taiwan sprayer. The results indicated that tebuconazole+trifloxystrobin, when applied via drones, exhibited the highest control efficacy against the brown spot, sheath blight, and sheath rot (47.8%, 77.4%, and 75.2% respectively). Moreover, combination treatment, i.e., tetraniliprole+(tebuconazole+trifloxystrobin), applied using a drone, achieved the most effective control (78.1%) against grain discoloration. Additionally, drone-based tetraniliprole application showed effectiveness against stem borer and whorl maggot (efficacy rates of 49.1%, 66.6%, and 60.7% for dead hearts, white ear, and whorl maggot, respectively). Overall, the pesticide combination treatment, i.e., tetraniliprole+(tebuconazole+trifloxystrobin), showed higher control efficacy against all the insect pests and diseases and recorded the highest grain yield of 7995 kg/hm2 with an incremental cost-benefit ratio (ICBR) of (1:5.63) when sprayed with a drone. Overall, this study underscores the potential of drone-assisted pesticide application in effectively managing multiple insect pests and diseases in rice, offering superior precision, efficacy, efficiency, and yield.