The purpose of plant quarantine is to protect disease-free agricultural areas by local restrictions on the movement of goods to prevent the introduction of plant pests and diseases. The underlying assumption is that the occasional inconvenience and expense of excluding a pest is better than its subsequent prolonged control.
In 1884 the Government, which was concerned at the danger of introducing pests and diseases to the colony, passed the Codling Moth Act of 1884, followed by the Orchard and Garden Pests Act of 1896. In 1897 it prohibited by Proclamation the importation of plants and fruits affected by any scale insects or by Queensland Fruit Fly, of vine cuttings affected by Phylloxera, and fruit attacked by codling moth. The Department of Agriculture administered the 1896 Act and, for the first time, inspected fruit and plants arriving in New Zealand at the principal ports of Auckland, Wellington, Lyttelton, and Dunedin.
Fumigation vaults were built at Auckland, Wellington, Christchurch, and Dunedin and remained in use until 1949. By 1904 it became necessary to replace the 1896 Act with the Orchard and Garden Pests Act, which was later to become the Orchard and Garden Diseases Act of 1908. Two inspectors were appointed for the North Island and one for the South Island. The Orchard and Garden Diseases Act, passed in 1928, repealed the 1908 Act, and further amendments became necessary in 1940 and 1950 because of changes mainly brought about by speedy air travel between one country and another. Surface travel had also speeded up. Thus the protection in time and distance which New Zealand had formerly enjoyed was broken down. It was now possible for adults of pests separated from their hosts to travel as stowaways in aircraft arriving from overseas.
The Amendment Act of 1950 brought the law up to date, led to new regulations in 1952, and enabled a full-time quarantine service, staffed by trained men, to function at all airports and ports of entry. These officers, who form the first line of defence against the introduction of diseases, meet all overseas ships and aircraft; board passenger ships in the stream, examine passengers' luggage, and inspect ships' cargoes and goods arriving by parcel post and mail. Plants growing in post-entry quarantine are also inspected for any signs of disease which might not be evident at the time of their arrival in this country.
Depending on the results of the examination at the port of entry, goods are either allowed free entry, entry under restriction of growing in post-entry quarantine, or fumigation or other treatment; or else they can be refused entry and either reshipped or destroyed. Since 1952, plants and plant products have been divided into three classes: (1) those safe to allow entry to; (2) those too dangerous to allow entry to; and (3) those which are allowed entry under certain conditions.
Most nursery stock falls into the last class. A prospective importer must apply to the Department of Agriculture for a plant-quarantine permit before importing the plants. A copy of this must accompany the plants to New Zealand, together with the International Health Certificate set out in the model certificate by the International Plant Protection Convention, 1951, of the FAO in Rome. On arrival at the port of entry the plants are inspected and, if found infested with any pests, are fumigated before being sent to their destination. At their destination most plants are planted into post-entry quarantine and remain there under inspection for any possible diseases for 12 months or more. If at the end of the quarantine period the plants are found clean and healthy they are released to the importer who may then propagate from them or sell them. If disease appears during post-entry quarantine they are either treated or destroyed. The cost of treatment and post-entry quarantine of goods is paid for by the importer.
When plants are considered too dangerous to be imported, they are prohibited, but if it is desirable to introduce a new variety there are special provisions to admit enough to allow for further propagation. Such plants must be grown under strict quarantine under the care of disease specialists.
The 1889 fumigation vaults have been replaced with modern fumigation stations at Auckland, Wellington, and Christchurch, with smaller ones at New Plymouth, Timaru, Dunedin, and Invercargill. Methyl bromide gas is used, either at atmospheric pressure or under vacuum. This gas is the most efficient present fumigant. It kills all stages of the life cycle of pests, without harming most plants or affecting foodstuffs.
by Gordon Arthur Henry Helson, M.SC., Chief Advisory Officer (Entomology), Department of Agriculture, Wellington.