Before 1877 no legal measures were available in the UK to prevent importation of plants infested with pests such as Colorado beetle. Measures taken at ports from that year onwards were brought together in the 1927 Destructive Insects and Pests Acts, empowering government officials to inspect and, if necessary, refuse plant imports. Within this Act, the ‘Sale of Diseased Plants Order’ placed on the grower the responsibility for recognition and reporting of serious pests and diseases, such as blackcurrant gall mite and silver leaf of plums. Lack of education and enforcement led to the need for specific orders relevant to particular current problems, such as in 1958 the fireblight-susceptible pear cultivar, ‘Laxton’s Superb’, was declared notifiable and prohibited under the Fireblight Disease Order.
Recent orders have helped prevent outbreaks of white rust on chrysanthemums, plum pox virus and two American leaf miner species; less success has been achieved with the Western flower thrip organism. Further importation legislation under the ‘1967 Plant Health Act’ prohibits the landing of any non-indigenous pest or disease by aircraft or post, and the ‘Importation of Plants, Produce and Potatoes Order 1971’ specifically names prohibited crops, such as plum rootstocks from eastern Europe, crops without a phytosanitary certificate, such as potato tubers from Europe, and crops that first need to be examined by inspectors, such as Acacia shrubs and apricot seeds.
The carrying out of these orders is supervised by the Plant Health Branch of the Department for Environment, Food and Rural Affairs (DEFRA). Complete success in preventing the introduction of damaging organisms may be limited by dishonest importations and by the difficulty of detection of some diseases, especially viruses. European Council directives, such as 77/93/EEC and 2000/29/EC, are moving member nations towards a unified approach in reducing the transfer of infected plant material across national boundaries, and the UK Plant Health Order (2005) implements the EC legislation. The Weeds Act 1959 places a legal obligation on each grower to prevent the spread of weeds such as creeping thistle, spear thistle, curled dock, broad-leaved dock and ragwort. In addition, under the UK Wildlife and Countryside Act (1981), it can be an offence to plant Japanese knotweed (Polygonum japonicum) and giant hog-weed (Heracleum mantegazzianum).
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