Whilst the research continues, the disease is still regarded as an important threat to UK woodland
Dead Oaks in a California forest
than their American cousins. This is not to say that trees have not been found affected by the disease - there have been cases on beech, horse chestnut, sweet chestnut and a number of non-native oak species. In most of these outbreaks the symptoms have been bleeding cankers similar to those found on the trees in America and, in almost all cases, the disease has spread to the tree from heavily infected plants of Rhododendron ponticum growing around it. P. ramorum spreads by means of
microscopic spores which, in wet conditions, are splashed from affected onto healthy plant tissue and germinate to create new infections. Sometimes large numbers of these spores are produced on infected rhododendron leaves. At present, our knowledge of P. ramorum is
far from complete. Whilst the research continues, the disease is still regarded as an important threat to UK woodland and heathland (common heathland plants such as bilberry are also susceptible). Fortunately, the numbers of confirmed cases of the disease in the UK are beginning to fall, as statutory action by the plant health authorities on nursery and amenity outbreaks starts to take effect. Anyone with susceptible plants in their care should remain vigilant, however, and should report any suspicious symptoms promptly.
Rhododendron dieback
Phytophthora kernoviae Another Threat.
What to do if you find Suspect Symptoms
Firstly, bear in mind that dieback of shrubs and bleeding cankers on trees can have a number of other causes. These include drought, and attack by other pests and diseases, including some other Phytophthora species that have been in the UK for many years. However, if you find symptoms that you believe could be due to P. ramorum or P. kernoviae you must report them to the relevant plant health authority (DEFRA in England and Wales, SASA in Scotland). Contact details, together with further information on the disease and excellent pictures of symptoms, can be found at
www.defra.gov.uk/planth/pestnote/sudden.htm
During inspections in 2003, plants of rhododendron and beech were found in southwest England with symptoms suggestive of P. ramorum. Laboratory tests, however, showed that a different Phytophthora species was responsible. This species was new to science, and has been given the name Phytophthora kernoviae (after Kernow, the dialect name for Cornwall, where the organism was first found). Where the organism came from is unknown, but it is regarded as posing a threat similar to P. ramorum. It seems to be more aggressive to rhododendron, and has also been found causing bleeding cankers on a couple of native oak trees.
Phytophthora kernoviae is also a Notifiable Disease, and suspected cases must be reported to the plant health authorities. So far, cases of this organism outside of nurseries have remained confined to a few sites in southwest England and south Wales.
Days OFF!
... or what Pitchcare readers get up to out of office hours
MIKE SEATON Managing Director of Weed Free, the Contract Pesticide Spraying organisation, and The Lawn Company. Mike has been in the Turf Grass industry since 1981 and it is well known that on his days off he tries to get as far away from grass and weeds as possible! He chose sailing as a hobby back in the early nineties. Having clocked up over 4,000 nautical miles in his logbook and sailed in and around The Solent, The Channel Islands and the Northern France peninsula, as well as taking sailing trips to Turkey, Greece, Croatia and The Canaries, he is not shy of a bit of bad weather or the occasional force 9 and sails all year round. Mike is also Commodore of The Royal Berkshire Yacht Club. “I’m just off to Tenerife to take my Coastal Skipper Practical course so when you read this I’ll be in my shorts in the sun (hopefully) being put through my paces!” When he’s not sailing yachts and dinghies Mike enjoys walking Charlie, his Basset Hound and Scamp his other dog in and around the Surrey countryside with the inevitable visit to a local pub en route! “My ambition is to buy a yacht, if only to say it was purchased for aquatic weed control.”
15
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96