Effect of vegetation on the longevity, mobility and activity of fipronil applied at the termiticidal rate in laboratory soil columns

Green nano-phytoremediation and solubility improving agents for the remediation of chlorfenapyr contaminated soil and water

Chlorfenapyr is a novel class of insecticide-miticide used for crop protection. It poses substantial risks to the reproductive ability of birds as well as environmental stability. This study was focused on the remediation of chlorfenapyr-polluted soil and water through the combined application of green nanotechnology, solubility improving agents and phytoremediation. An analysis using electron microscopy showed that the green synthesis resulted in circular ficus iron nanoparticles (F-Fe⁰) with diameters of 2.46 nm-11.49 nm, while the ipomoea-silver (Ip-Ag⁰) and brassica-silver nanoparticles (Br-Ag⁰) were circular, cubical, hexagonal, triangular and rod -like in shape with sizes ranging from 6.27 to 21.23 nm in IP-Ag⁰ and from 6.05 to 15.02 nm in Br-Ag⁰. After 24 h of treatment with F-Fe⁰, Ip-Ag⁰ and Br-Ag⁰ supported on activated charcoal (Ach), the chlorfenapyr in the aqueous solution was reduced to 86%, 79.70%, and 79.70%, respectively, compared to the 6.16% in aqueous solution. Moreover, after 24 h of treatment with Plantago major plus F-Fe⁰Ach, P. major plus Ip-Ag⁰Ach, and P. major plus Br-Ag⁰Ach, the chlorfenapyr in the aqueous solution was reduced to 93.7%, 91.30%, and 92.92%, respectively, as compared to the 69.27% in P. major. After four days of exposure, the percentage of chlorfenapyr degradation in the soil (i.e. control) only reached 12.40%,while the degradation rates were enhanced by 71.22%, 57.32% and 73.10%, respectively, in the presence of P. major plus nanoparticles (F-Fe0, Ip-Ag0 and Br-Ag0). The integration of green nanotechnology, solubility-improving agents, and phytoremediation by Plantago major has played a major role in the remediation of soil and water contaminated with chlorfenapyr.

Isolation and Characterization of an Endophytic Fungal Strain with Potent Antimicrobial and Termiticidal Activities From Port-Orford-Cedar

Termites are responsible for an estimated US$1 billion annually in property damage, repairs, pest control, and prevention. There is an urgent need of finding a better alternative way to control and prevent termites. Port-Orford-Cedar (POC) has been known to have significant levels of natural durability and termiticidal activities due to its extractive contents. In this study, 25 endophytes including 22 fungal and 3 bacterial strains were isolated from the POC. Four strains, namely, HDZK-BYF21, HDZK-BYF1, HDZK-BYF2, and HDZK-BYB11, were chosen to test their termiticidal activities. The fermentation broth of strain HDZK-BYF21 displayed the potent antimicrobial and termiticidal activities. Morphological examination and 18 S rDNA sequence analysis demonstrated that strain HDZK-BYF21 belonged to the genus Aspergillus. This finding indicates the existence of an interesting chemical symbiosis between an endophytic fungus and its host. This is also the first report on endophytes isolated from the POC that may have potential termiticidal activities. Endophytes with termiticidal activities can be grown in bioreactor to provide an inexhaustible supply of bioactive compounds and thus can be exploited commercially.

Mobility, longevity and activity of chlorfenapyr in soils treated at a termiticidal rate

BACKGROUND

The mobility, longevity and termiticidal activity of chlorfenapyr applied to soils at the termiticidal labeled rate was evaluated for 30 months after treatment (MAT) in a greenhouse study.

RESULTS

There was little dissipation of chlorfenapyr in soil treated at the labeled rate for perimeter treatments for the prevention and control of termite infestations. Chlorfenapyr was detected in soil immediately below the initially treated soil in the packed soil columns. This was likely due to settling of soil. The treated soil remained toxic to subterranean termites in 3 and 7 day bioassays over the duration of the study. The treated soil displayed slow-acting properties regarding toxicity to termites. Trace amounts of chlorfenapyr were detected in the eluates of packed soil cones.

CONCLUSION

The commercial formulation of chlorfenapyr used in this study (21.45% concentrate diluted to 0.125% prior to application) killed 100% of the tested subterranean termites for at least 30 months.

Bifenthrin longevity at the termiticidal application rate

BACKGROUND

The longevity, mobility and insecticidal activity of bifenthrin at the termiticidal application rate for perimeter treatment were investigated in packed-soil columns in the laboratory and greenhouse.

RESULTS

Bifenthrin was not detected in the eluates of packed-soil cones over a period of 6 months. In larger pipe plots incorporating bifenthrin into the top 15 cm of the soil, the compound degraded in a biphasic fashion. Within the treated soil, the effect of vegetation on the amount of bifenthrin remaining in the soil depended on soil depth and time, and soil half-lives were longer in non-vegetated soil. Bifenthrin residues were higher in the top 7.5 cm of soil and declined over time. Movement of bifenthrin into the top untreated soil depth was observed, but much less was observed in lower depths. The soil remained toxic to termites in 3 day and 7 day forced exposure bioassays for the 30 month duration of the study.

CONCLUSIONS

Concentrations of bifenthrin will remain in the soil at levels sufficient to kill termites for more than 30 months.