Biopesticides based on plant extracts offer a promising alternative to the use of conventional synthetic pesticides. However, biopesticide products must provide acceptable levels of control. To date, few studies have investigated the efficacy of biopesticide products under conditions that reflect commercial practice. Here we report results from three experiments, one completed under glasshouse conditions in 2014 and two completed under polytunnel conditions, in 2015 and 2016, respectively. These experiments tested the efficacy of three terpene based biopesticides used to control two aphid species, peach-potato aphid (Myzus persicae) and melon and cotton aphid (Aphis gossypii), on ornamental crops. The three biopesticide products tested were orange oil (60 g active ingredient per litre, formulated as a soluble liquid), the essential oil from Chenopodium ambrosioides variety nr. ambrosioides (16.75% active ingredient, formulated as an oil dispersion) and neem oil (1% active ingredient, formulated as emulsifiable concentrate). The biopesticides tested were applied as foliar sprays using a water volume of 600 l/Ha and all experiments were done at Harper Adams University, Shropshire, UK. The biopesticide products tested gave statistically similar levels of control of M. persicae populations on pansy plants as the conventional synthetic insecticide flonicamid (500 g/kg active ingredient, formulated as a wettable granule) and spirotetramat (150 g/l active ingredient, formulated as an oil dispersion). All products reduced numbers of aphids by at least 85% during the experimental period. Orange oil also gave a similar speed of kill to flonicamid and was faster acting than spirotetramat, two conventional synthetic insecticides that are widely used to control aphid pests of ornamental crops. Against A. gossypii on Hebe, orange oil gave similar levels of control (90% reduction in aphid numbers) as flonicamid (98% reduction in aphid numbers), when applied with a spray interval of three days (as per label recommendation). The essential oil from Chenopodium ambrosioides variety nr. ambrosioides was not as effective as flonicamid but did significantly reduced (80% reduction in aphid numbers) numbers of A. gossypii on Hebe compared to a water control when applied with a spray interval of five days. Neem oil was not effective against A. gossypii. Importantly, there was little evidence of any phytotoxicity caused by any of the biopesticide products tested. The potential to use these products as part of an Insecticide Resistance Management (IRM) programme are discussed.