Brassica crops may be infested and infected by a wide range of pest and pathogen species. For example, as many as 50 species of insect from several orders (Diptera, Coleoptera, Lepidoptera, Thysanoptera, Hemiptera) are considered to be Brassica pests. Some of these species are specialists in that they colonise plants from the Brassicaceae and close relatives, whilst others, such as Myzus persicae are generalists and colonise hosts from a range of plant families. Plant pathogens are Brassica specific, with none of the main fungal, viral, or bacterial species listed elsewhere in the report having host species outside cruciferous plants. Brassica crops are also invariably challenged by pressure from weed species, which are from a diversity of plant families. According to EU DIRECTIVE 2009/128/EC, Integrated Pest Management (IPM) ‘means careful consideration of all available plant protection methods and subsequent integration of appropriate measures that discourage the development of populations of harmful organisms and keep the use of plant protection products and other forms of intervention to levels that are economically and ecologically justified and reduce or minimise risks to human health and the environment’. Whilst farmers and growers endeavour to take a ‘holistic’ approach to crop production and the need for a holistic approach is also implied by IPM, it is unlikely that many producers and their advisors consider the impact of any one management action on the ‘whole crop’. For example, since pyrethroid insecticides are relatively cheap and effective against many species of Lepidoptera, they may be used as a product of first choice for caterpillar control. However, because pyrethroid insecticides also have a broad spectrum of activity, they are likely to kill non-target species that they contact, including natural enemies that may be contributing to the suppression/control of other pests. It is unlikely that many growers take account of this (or have sufficient information to know how to take account of this) when deciding which treatment to apply. In field trials during the last 10 years at Warwick Crop Centre in the UK, the ‘side effects’ of pyrethroid insecticides have led to larger numbers of Thrips tabaci, Myzus persicae and Delia radicum in pyrethroid-treated plots than in insecticide-free control plots (Rosemary Collier, unpublished data). Similar results were obtained in field experiments done by the Julius Kühn-Institute in Germany, when the insecticide Spinosad was used intensively to control caterpillars. In the Spinosad-treated field plots infestation by the cabbage aphid Brevicoryne brassicae was much higher than in the untreated plots (Hommes & Herbst, 2014). Thus, for the control lepidopteran larvae, the use Bt products might be more economic: the higher prices for Bt products might be compensated for by the reduced need for treatments against secondary pests. Other research has shown that the broad spectrum insecticide Spinosad, which is also approved for use on organic crops in some countries, may have adverse effects on non-target and often beneficial species (e.g. Viñuela, et al., 2001).