18 THE WILTSHIRE ARCHAEOLOGICAL AND NATURAL HISTORY MAGAZINE 
The three genera Crataegus (Hawthorns, 
Cockspurthorns), Malus (Apples), and Sorbus 
(Rowans and Whitebeams) each provide seven or 
eight tree types, and there are a further six Rosaceae 
tree genera to be seen near College buildings. 
This family is represented therefore by very 
common native trees and shrubs (eg Hawthorn, 
Sloe, Gean), by common semi-naturalized species 
(eg Cherry and Portugal Laurels) and lastly by 
individual old and new small-tree garden favourites 
(eg Japanese Cherries, Purple-foliaged Asiatic 
Apple hybrids, Quince (Cydonia), Medlar 
(Mespilus) etc). Of the last group, only the beautiful 
Double-flowered Pink Japanese Cherry (Prunus 
‘Kanzan’) was common, conspicuous in spring 
because of the dense massed pink blossoms. 
DISEASES 
1. Aesculus carnea (nos.149 ,150) 
These Red Horse Chestnuts are susceptible to a 
degenerative canker. Several College trees are 
affected with the huge trunk ulcers, with raised 
edges, up to 40cm in diameter. They are often 
irregular, and can coalesce with adjacent ulcers. 
Underneath the larger, older ulcers, the wood can 
be crumbly. Grafted trees only have the canker 
ulcers above the graft union. One such tree has 
been recently felled. The cultivar ‘Briottii’ (no. 
150) is so far unaffected, and could be a resistant 
variety. 
2. Quercus robur 
Over the last three years, a severer form than hitherto 
of Oak-Dieback Disease (ODBD) has afflicted 
numbers of English Oaks. It is an incompletely 
understood condition in which the organism 
Phytophthora, normally present and harmless in the 
soil becomes virulent and attacks the Oak roots. 
ODBD is thought to be a multi-factorial illness, 
with water levels and climatic conditions affecting 
the type and pathogenicity of the soil Phytophthora; 
however additional and unknown factors also 
operate. Several Oaks, all Q.robur, in the Nature 
Trail mixed-woodland have been affected and show 
the characteristic ‘Stagshorn’ effect of some dead 
branches in the crown. Occasionally part of a living 
branch has the small, yellowing leaves and weak 
shoots characteristic of a renewed attack of ODBD. 
One Q.robur in the Nature Trail woodland has been 
killed by ODBD, but most such Oaks of this species 
co-exist with mild or occasionally moderately 
severe relapses from the illness. The Durmast Oaks 
(Q.petraea, no. 43), Hybrid Native Oaks (Q. x 
rosacea, no. 45) and the other Oak species (see nos. 
40-46) within the College grounds are not (or 
hardly) affected by ODBD. This is exactly the same 
pattern as occurs in Savernake Forest. 
3. Ulmus species 
Dutch Elm Disease (DED) is caused by the 
synergistic (mutually enhancing) co-operation 
between the vectors, two species of bark beetle 
(Scolytus scolytus and S-.multistratus), and the 
pathogenic fungus, Ophiostoma (or Ceratocystis) 
novo-ulmi. In turn, the fungus itself can be killed by 
‘d-factor’ strains. The d-factors are cytoplasmically 
transmitted ‘virus-like’ pathogens of fungi, 
mitochondrial double-stranded RNA elements. 
Unfortunately the d-factors have not been infective 
enough to eliminate the colonies of fungi spread 
between Elm branches and trees by the highly 
mobile beetles. As a consequence DED has spread 
remorselessly. 
No mature English Elms (Ulmus procera, no. 98) 
survive anywhere within the College grounds, but 
the residual root suckers are common and vigorous 
along some hedgerows, boundaries, waste places 
and wooded edges. Beetle galleries are to be seen 
under the bark of dead and dying young trunks. 
Mature but young Wych Elms (Ulmus glabra) often 
survive to fruition in the grounds, but succumb to 
DED before they reach their full size and girth. So 
far, two smaller Wych Elm cultivars (“(Camperdown’ 
and ‘Lutescens’) are unaffected by DED. Along the 
south-western boundary of the Cotton House 
southern garden, a Hornbeam-leaved Elm (Ulmus 
minor ssp carpinifolia, no. 97) survives as a largish 
tree, with numbers of additional hedgerow suckers. 
We thought it could be resistant to DED, but one 
small upper branchlet seemed to show the sinister 
yellowing of leaves in the summer of 2002. 
4. Salix species, especially S. fragilis. 
Two fungal diseases are often found together on the 
same tree, and this is the case in some of the 
Marlborough College Willows. These are willow 
scab and black canker, caused by Pollacia saliciperda 
and Glomerella miyabeana (Rose 1989, 2003). 
Curled blackened shrivelled leaves in early or 
midsummer lead to die-back of shoots, often 
reducing in time potential Willow trees to scrubby 
ugly shrubs. Of the willows listed between nos. 75 
and 88, in order of severity the following four types 
are attacked: Crack Willow, Corkscrew Willow, 
