The efficacy of plasma-treated tap water (PTW) for the possible treatment of a mealybug (Planococcus citri) infestation was studied under laboratory conditions. Mealybugs growing on Nerium oleander have been treated using PTW after being transferred to Petri dishes, thus avoiding possible buffering effects that might occur in an in-situ study. When treating tap water with a dielectric barrier discharge for several minutes (1, 3, 5 and 10 min) a distinct acidification of the water can be determined, resulting in a pH value of 1.8 after 10 min treatment. The efficacies of the treated tap water samples were compared to the efficacies achieved using classically acidified water. The classical acidification of tap water was carried out using nitric acid and hydrochloric acid to see any possible influences of the salt of the acid in question. The application of PTW revealed high mortality rates of approx. 90% after an observation period of 24 h. PTW appears promising for the treatment of smaller plant stock and commodities as produced by small scale farmers or in greenhouses as an environmentally friendly substitute or supplement to conventional pesticides.

Bovine digital dermatitis is an important infectious claw disease caused by multimicrobial infections with bacteria such as Fusobacterium (F.) necrophorum or Porphyromonas (P.) levii. To analyze the antibacterial effects of a TRIS-buffered plasma-activated water (Tb-PAW) on the bacterial number of F. necrophorum, P. levii, Escherichia (E.) coli, Staphylococcus (S.) aureus and Clostridium (C.) sporogenes 1 mL of each bacterial solution (106–108 CFU/mL) was incubated with 9 mL Tb-PAW up to 15 min. E. coli, F. necrophorum and P. levii were significantly reduced by 5.0 log after 1 min of treatment, while S. aureus and C. sporogenes required 15 min to reach a 3.0 log reduction. The addition of bovine serum albumin did not negatively affect the bactericidal effect. Tb-PAW storage at 7 °C and 21 °C is possible for up to 24 h without any change in the bactericidal effect, while Tb-PAW stored at 30 °C can only be used for a period of 12 h. The present data indicate that Tb-PAW can be used to reduce various bacteria even under the influence of different parameters. However, due to the complexity of Tb-PAW, further studies are required to ensure its microbicidal activity before practical application.