EnviroSpin Watch

The Government is acting correctly over Sudden Oak Death (SOD).....

Now you won't often hear me say this, but, sorry, gardening lads and lassies: the Government is acting absolutely correctly on this one - the threat of Sudden Oak Death (SOD): 'Oak rescue bid "may ruin growers"' (BBC Online Science/Nature News, June 1).

Here's part of what I wrote recently in an article, 'A new plague hangs over Britain's trees', for Country Illustrated magazine (Issue 69, May, 2004, pp. 78-85):

"In April 2002, the UK recorded its first infection, on Viburnum at a garden centre. There are now over 300 recorded outbreaks. In January 2004, the Royal Horticultural Society depressingly found it lurking in its famous garden at Wisley in Surrey, where the pathogen was noted on a Viburnum x bodnantense, growing among rhododendrons. To date, the disease has been noted in the UK on beech trees (Fagus sylvatica), Camellia, horse chestnut (Aesculus hippocastum), lilac (Syringa vulgaris), Pieris, rhododendrons, sweet chestnut (Castanea sativa), Viburnum, Virginia witch hazel, and yew (Taxus baccata), the last in pots. It has also, even more alarmingly, been discovered in three introduced species of oak (Quercus), namely the evergreen holm oak (Quercus ilex), the southern red oak (Quercus falcata), and the Turkey oak (Quercus cerris). At the time of writing, however, there are no reports of it having infected either of our two native species of oak, the pedunculate oak (Quercus robur) and the sessile oak (Quercus petraea), or their many hybrids. The Forestry Commission has urgently begun a survey of 1,000 woodland sites throughout the UK to establish a better understanding of the potential scale of the threat.

Meanwhile, it must be fingers crossed, although the omens are not propitious. Everything about this new threat hints that it could prove devastating. First, unlike 'Dutch Elm Disease', the pathogen is able to infect a large range of unrelated plant species from many different plant families. It is an especial worry that it can employ garden plants as 'stepping stones' and 'reservoirs' for its spread, and most UK locations where it has been found appear to be closely associated with either rhododendrons or Viburnum. In the United States, the disease has recently attacked commercial conifer species, which is deeply concerning for our forestry industry, dependent as it is on species like the Sitka spruce (Picea sitchensis).

Secondly, the disease seems to be distributed quickly and effectively by many agents of dispersal, including water, wind, and infected timber. This again sets it apart from 'Dutch Elm Disease', which depended on special animal vectors, the two Scolytus beetles, for its spread. Phytophthora ramorum, by contrast, thrives in warm, humid woodlands and shrubberies, where it can be dispersed in rainwater, by local breezes, and through infected cuttings.

Thirdly, it is a newly-discovered organism. This means that there are, to date, no known generic cures or preventatives for the disease. These will need time to develop and to be tested for their effectiveness and safety. In America, the threat has become so serious that the California Department of Pesticide Regulation has given fast-track approval to one special experimental registration, which, however, only acts as a preventative and not as a cure. Beyond this, there is no guarantee that any currently-available general chemical pesticide or 'fungicide' will work successfully.

What then needs to be done in the UK? First, the international import of potential host plants and timbers must be strictly regulated. In 2001, when the European pathogen was established as relating to that infecting the American oaks, Britain introduced plant passports for the import of rhododendrons and viburnums, two of the most virulent carriers. The EU followed this example in November 2002. We now urgently need plant passports for a whole range of implicated garden plants and shrubs, including Camellia, Pieris, and cultivated yews. Timbers from a number of potential hosts must also be strictly monitored on entry.

Within Britain itself, immense care must be taken not to spread the pathogen from diseased plants. Local dispersal is likely to be natural, through wind and rain; long-distance dispersal of the pathogen, however, probably relies on human agency. Any infected material must be dealt with in situ and it must never be taken to an uninfected area. Cuttings should not be left by roadsides or in any location where they might be picked up. Care must be taken with the planting of any implicated garden or shrub species, such as rhododendrons and viburnums, with no new plantings at all being made near to oaks and beeches. All nurseries should be fully-informed about the disease and all current nursery stocks of relevant species thoroughly inspected. This programme must be supported by the intensive inventory of forests, woodlands, and isolated specimen trees. Landowners must also be cautious about the trimming of ornamental yews and other relevant species. It is vital to remember that the pathogen spreads locally through wind-blown or water-borne 'spores'. Finally, urgent scientific research is needed into new pesticides for prevention and cure, possible biological controls, and resistant tree and shrub strains. Genetic modification may also prove helpful in the battle."

I'm afraid it's a SOD indeed, but, as I concluded: "The thought of a landscape without oak and beech and chestnut is too painfail to contemplate."

For once, gardening and gardeners will have to exercise extreme care and restraint.

Philip, unusually totally with Government. Why worry about GM, when every disease and exotic can enter through the back door!