H. WaRMALD KJl 



tree. The affected trees were in two rows ; along one side of them was 

 a row of the variety Warner's King bearing a few diseased trusses while 

 along the other side the trees (Newton Wonder) were apparently quite 

 free from the disease. This would appear to indicate that the Lord 

 Derby variety is particularly susceptible to the disease and this con- 

 clusion is supported by the fact that in one large orchard where there 

 were some hundreds of trees of this variety together with several other 

 varieties it was possible to detect the Lord Derby trees even in winter 

 by reason of the large number of dead spurs and twigs which they bore. 

 In the Weald of Kent where this variety is extensively cultivated so 

 much injury has been caused by the disease that it has been necessary 

 in some cases to "top-graft" the trees with a more resistant variety. 



Not only are well-established trees attacked, but quite young trees 

 too are susceptible to the disease. In one case, observed in the fruit 

 plantation at Wye College, a young cordon apple tree (of the variety 

 Rival) was attacked through a fruiting spur situated near the middle 

 of the stem during the first season after it was planted out; a canker 

 developed round the base of the affected spur and killed the upper half 

 of the tree. 



The first symptoms of the disease are noticeable about a fortnight 

 after the tree comes into flower; it will then be observed that some 

 "fruiting spurs'' of the trees affected not only fail to set fruit but the 

 flowers and leaves round the base of the inflorescence show evidence of 

 wilting, and, within a few days become dry and withered. Where such 

 a truss is borne on a short spur there will be found about the middle of 

 June a depressed, often cracked, canker-like area on the branch, around 

 the base of the spur. In some instances the canker within a few weeks 

 girdles the branch and so causes the death of that portion distal to the 

 canker. 



Usually no external sign of any parasitic organism is to be found on 

 these newly killed spurs at this stage. During periods of wet weather 

 however the dead flowers and pedicels may produce pustules bearing 

 chains of elliptical to citriform conidia which are readily identified as 

 of the Monilia type. Again if sections are made through the base of 

 a dead truss, showing externally no trace of the fungus, and examined 

 microscopically, hyphae are invariably to be found. When particles 

 of these sections are placed on nutrient culture media the fungus con- 

 tinues to develop and may be induced to produce conidia when growing 

 in pure culture ; under these conditions too the organism is recognised 

 as a Monilia. 



