Combined Effect of Entomopathogens against Thrips tabaci Lindeman (Thysanoptera: Thripidae): Laboratory, Greenhouse and Field Trials

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae) is one of the most damaging insect pests of onions, Allium cepa L., which is an economically important agricultural crop cultivated worldwide. In this study, the combined application of entomopathogenic nematodes with entomopathogenic fungi against different soil dwelling stages of T. tabaci was evaluated. The nematodes included Heterorhabditis bacteriophora (VS strain) and Steinernema feltiae (SN strain), and fungi included Beauveria bassiana (WG-11) and Metarhizium anisopliae (WG-02); all four paired combinations (nematode + fungus) were included. In a small cup bioassay, only the combined application of H. bacteriophora and B. bassiana (WG-11) caused a synergistic interaction against pre-pupae, while all other combinations were compatible in an additive manner against pupae and late second instars. In a larger arena, a potted soil bioassay, again, combined applications of both pathogens produced greater mortality compared to single applications of each pathogen; all the combinations exhibited additive interactions, with the highest mortality observed in pre-pupae, followed by pupae and late second instar larvae using H. bacteriophora and B. bassiana (WG-11). Additionally, in the potted plant bioassay, lower adult emergence was observed from treated groups compared to control groups. Under field conditions, lower numbers of adults and larvae were found in treated groups relative to controls. Overall, the pre-pupal stage was more susceptible to the pathogen treatments, followed by pupae and late second instar larvae, and also combined applications of both pathogens suppressed the adult population. Combined application of entomopathogenic nematodes and fungi could be used for integrated pest management (IPM) of T. tabaci in onion production systems

Environmental tolerance of entomopathogenic nematodes differs among nematodes arising from host cadavers versus aqueous suspension

Environmental factors such as temperature and desiccation impact the survival and efficacy of entomopathogenic nematodes (EPNs). Most studies on environmental tolerance have focused on EPNs applied in aqueous suspension. Another approach for EPN application is via infected host cadavers. Emergence in host cadavers is also more representative of nematodes in natural populations. In prior studies, certain advantages in fitness have been observed with the cadaver application approach relative to aqueous application, yet the impact of environmental stress on these approaches requires investigation. In this study, we compared the effects of various temperatures (heat and cold) and desiccation intervals (48 and 72 hr) on the survival, virulence and reproductive capacity of Heterorhabditis bacteriophora and Steinernema glaseri when applied via cadaver versus aqueous suspension. In the heat tolerance bioassays, following exposure to 30 degrees C, 35 degrees C and 37. 5 degrees C, nematodes (from both species) in the cadaver treatments exhibited higher survival, and reproductive capacity compared with aqueous application. No survival was observed above 37.5 degrees C regardless of species or application approach. In cold tolerance, no differences were observed between the cadaver and aqueous treatments after a sequence of exposures from 10 degrees C to -2 degrees C. In desiccation assays, following exposure to 85% relative humidity for 2 or 3 days, nematodes (from both species) exhibited higher survival and reproduction in the cadaver treatment than in the aqueous treatment, whereas no differences were observed in virulence. This is the first study to find differential stress tolerance among nematodes emerged from infected host cadavers versus those applied in aqueous suspension. Our findings indicate additional advantages when using the cadaver approach for biocontrol applications, and suggest EPNs existing in natural populations may have broader environmental tolerance than those applied via aqueous suspension.Higher Education Commission (HEC) IslamabadHigher Education Commission of Pakistan; Adnan Menderes UniversityAdnan Menderes University [ZRF-15012]Sehrish Gulzar and Muhammad Usman thank the Higher Education Commission (HEC) Islamabad for providing financial support through their International Research Support Initiative Program (IRSIP) research grant program. The authors also thank Stacy Byrd for technical assistance. This study was supported by Adnan Menderes University (project no: ZRF-15012).WOS:0005714734000092-s2.0-85089217696PubMed: 3276323

In vitro assessment of the protection from oxidative stress by various fractions of Artemisia incisa Pamp.

The methanolic extract of Artemisia incisa Pamp. was dissolved in distilled water and successively partitioned with n-hexane, chloroform, ethyl acetate and n-butanol. The antioxidant potential of all these fractions and remaining aqueous fraction was evaluated by four methods, i.e., the scavenging activity of the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), the total antioxidant activity, the ferric reducing antioxidant power (FRAP) assay and the ferric thiocyanate assay. In addition, the total phenolics was determined. The obtained results revealed that among the studied fractions the ethyl acetate soluble fraction showed the most potent DPPH-radical scavenging activity with an IC50 value of 5.3 ± 0.71 μg mL-1, which is even more effective than the standard antioxidant butylated hydroxytoluene (BHT) (IC50 value 0f 12.1± 0.92 μg mL-1). The ethyl acetate fraction also showed the highest FRAP value (3677.13 ± 27.1 μg TE mL-1), inhibition of lipid peroxidation (60.93 ± 0.84 % at 500 μg mL-1) and total phenolic content (95.5 ± 0.05 μg GAE g-1) as compared to other fractions. However, the remaining aqueous fraction was found to posses the highest antioxidant activity of all the fractions