Biosecurity is very important
From New Zealand Tree grower February 2015
During my Canadian secondment from 1992 to 1994, I attended a meeting addressed by the then Chief of the USDA Forest Service who talked about the major biological threats to North American forests. Below are listed some of the major introduced biological threats, now updated, together with a brief description.
- Gypsy moth Lymantria dispar – This was introduced in 1868 for its silk spinning caterpillars but escaped soon afterwards. Now it is one of the most destructive insects in the eastern United States defoliating about 400,000 hectares of hardwoods each year.
- Kudzu Pueraria lobata – It is known as the vine that ate the south. It was introduced from Japan in 1876 to stabilise road cuttings and later promoted as a landscape vine. It smothers trees and kills them and can grow at a rate of a 30 cms a day. Now it covers three million hectares in south eastern United States.
- Chestnut blight – This is caused by a pathogenic fungus Cryphonectria parasitica which was accidentally introduced around 1900 possibly on imported Japanese chestnut nursery stock. By 1940 almost all mature eastern American chestnut trees had been killed, estimated to be four billion trees. The once common chestnut was praised for its fruit and its beautiful, decay-resistant wood.
- White pine blister rust Cronartium ribicola – A fungal disease which kills five-needle pines also called white pines. It was accidentally introduced from Europe in 1909 and alternative hosts are currants and gooseberries. Although white pines Pinus stobus and P. monticoli are often fast growing, there are few mature white pines left alive in the United States and Canada.
- Dutch elm disease – This is a vascular wilt fungus Ophiostoma ulmi spread by elm bark beetles. It was accidentally introduced from Europe in 1928. Avenues of handsome elms which were once common in many cities are no more.
- Emerald ash borer Agrilus planipennis – A native of Asia and eastern Russia it was unintentionally introduced in 2002 probably in ash wood used to stabilise crates during shipping. It has greatly reduced or even eliminated the ash timber industry in eastern United States, once estimated as being a $25 billion a year industry. There are now fears that the borer will attack fringe plants of the same ash family such as forsythia and lilac.
Our relative isolation combined with our very strict border biosecurity has meant that New Zealand has generally escaped devastating introductions in forestry, agriculture and horticulture. I compare our strict biosecurity controls to vaccinations against such devastating diseases as diphtheria, tetanus and polio. When almost no-one suffers from such devastating diseases for decades, the public can become apathetic and complacent about the need for vaccinations. We may be sometimes inconvenienced by our strict biosecurity checks but the United States forestry examples convincingly show what could happen if imports are not subject to close inspection.
On a recent visit to Chile I was horrified to find some radiata stands there unhealthy and defoliated. The cause was Phytophtheria pinifolia. We want to ensure that pathogen is never introduced into New Zealand. Every visitor to Chilean pine plantations should declare their footwear on arrival in New Zealand and have their clothes dry cleaned as soon as possible after arrival.
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Disclaimer: Personal views expressed in this blog are those of the writers and do not necessarily represent those of the NZ Farm Forestry Association.