Investigations concerning the effect of hemp oil on mortality of the foxglove aphid (Aulacorthum solani Kalt.) and the two spotted spider mite (Tetranychus urticae Koch) were conducted in the years 2014-2015. The tested essential oil was produced at the Institute of Natural Fibers and Medicinal Plants in Poznan. It was obtained by steam distillation of fresh panicles of Polish hemp cultivars, Beniko, Bialobrzeskie and Silesia, with low cannabinoid contents, including THC (max. 0.2% plant fresh matter). The effect of essential oil on the investigated pests was determined following the application of aqueous emulsion solution at 0.02, 0.05 and 0.1%. Mortality of agrophages was determined 24, 48 and 72 h after treatment. In this study a very high efficacy of the essential oil produced from hemp panicles was found in the reduction of population size of the foxglove aphid (A. solani). Already at 24 h after its application at a concentration of 0.1% pest mortality rate was 98.20%, while after 48 h it reached 100%. A significant, although much lesser effect of oil on the aphid population was recorded when applying it at 0.05%, with the mortality rate of the true bug after 72 h amounting to 57.33%. Essential oil also showed an effect on the two spotted spider mite (T. urticae). Following the oil application, irrespective of its concentration, a significant effect on mite mortality was observed. Its action was the strongest at its highest concentration, ie 0.1%, while mortality of the pest at 24, 48 and 72 h after treatment was 83.28, 95.83 and 98.72%, respectively.
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