Use of synthetic acaricides is hampered by pest resistance & product withdrawals

1. The Influence of dust and humidity on the toxicity of plant essential oils to the poultry red mite (PRM) Diane Holmes, School of Agriculture, Food & Rural Development, Newcastle University, UK . Email; diane.holmes@ncl.ac.uk Use of synthetic acaricides is hampered by pest resistance & product withdrawals More research is needed to assess the potential of plant essential oils as acaricides Aim ● The aim of the current project was to examine whether the toxicity of essential oils to PRM was affected by a range of humidity & dust levels & any interaction between them. ● PRM is a serious pest of laying hens. Due to problems concerning pesticide resistance & withdrawal, alternative & reliable means to manage PRM in laying flocks are being sought. Essential oils contain chemicals toxic to pests. E.g. linalool from lavender Lavender It may that the efficacy of essential oils is affected by environmental factors such as dust & humidity Essential oils have been investigated for control of PRM with promising results from toxicity testing in the lab Conclusions ● ANOVA & further Tukey’s Tests confirmed that the two oils were toxic to PRM & that both high dust & high humidity could increase essential oil toxicity to PRM. ● There was no interaction between humidity & dust effecting mite mortality. There was an interaction between humidity & oil. ●Dust & humidity interactions shouldn’t effect the efficacy of essential oil-based products against PRM, probably as one has an over-riding effect on the other. Methods ● Combinations of 3 dust & humidity levels (ambient, moderate & high) were used to see if they would effect the toxicity of 2 essential oils; clove bud & cinnamon bark, to PRM. A no-oil control treatment was also included. ● LD50’s for the essential oils were determined at ambient dust & humidity levels & used to expose PRM to oils at the various dust x humidity levels in Petri dishes according to methods in George et al. (2009). ● For dust; ambient = 0 mg, moderate = 9 mg, high = 18 mg dust per dish (after George et al. 2009). For humidity; ambient = 0 µl, moderate = 4 µl, high = 23 µl water per dish. Results GLM ANOVA OUTPUT; Dust; P < 0.05. Humidity; P < 0.001. Oil; P < 0.001. Humidity x oil; P < 0.001. Dust x oil; not sig. Dust x humidity; not sig. Figs. Mortality (%) of PRM exposed to; 1. the control 2. clove bud (0.116 mg oil/cm² Petri dish base) & 3. cinnamon bark (0.062 mg oil/cm² Petri dish base) at different dust & humidity levels. N = 8 for all means. Acknowledgements; Work was funded by a Newcastle University (UK) Vacation Scholarship as part of MITEeHEN, a Defra-funded study . Images used were sourced from the following locations; Insecticide=amazon.com; toy mite=profesoraloca.vox.com; superman symbol=comicbookcloset.com; lavender=alphazero.web.aplus.net; essential oil=thebodyshop.com. Reference; George et al., 2009. Med Vet Entomol, in press.