37 



WITHES-TIP AND BROWN ROT OF PLUMS AND 

 CHERRIES. 



(Manilla cinerea, forma pruni.) 



The decay of ripe plums known as Brown Rot is a disease 

 familiar to all growers. It is a serious trouble wherever plums 

 are cultivated, and the losses occasioned, both on the 

 trees and in market consignments, are often very heavy. 

 Quite as serious, and at times more serious, is the attack by the 

 Brown Rot fungus on the flowers and shoots. This form of 

 attack, which is known as " Blossom-Wilt and Wither-Tip " 

 respectively, has only recently been recognised and carefully 

 studied. The details of the various Brown Rot fungi and then- 

 method of attack have been followed with extreme care and 

 minuteness by Dr. H. Wormald, of Wye College, to whom 

 practically the whole of our knowledge of Brown Rots, as they 

 occur on fruit trees in this country, is due, and on whose work 

 this leaflet is based. 



The fungus concerned in the various attacks on plums is 

 Monilia cinerea, forma pruni. It is a form of this same species 

 (M. cinerea, forma mali) which causes the Blossom- Wilt of 

 apple. The two forms, however, are quite distinct. The plum 

 form is apparently unable to cause Blossom- W T i It of apples and 

 the apple form has not been found on plums. When the 

 number of apple orchards interplanted with plums is con- 

 sidered, this fact should be a matter of considerable satisfaction 

 to growers. 



Brown Rot of cherries is caused by the same fungus as 

 Brown Rot of plums, and in this case, also, it attacks the 

 blossom and the wood as well as the fruit. The description 

 given in this leaflet, and also the control measures recom- 

 mended, would apply equally to cherries. 



Blossom-Wilt. The Brown Rot fungus produces a 

 Blossom-Wilt of plums similar to that found on apples (see 

 Leaflet 312). In the spring, spores derived from the mummied 

 plums (Fig. 1) on the trees, and from spore-pustules on infected 

 wood, are blown on to the flowers. The spores readily infect 

 the stigma, and the mycelium of the fungus passes down the 

 style and causes the death of the flowers (Figs. 2 and 3). The 

 mycelium subsequently passes through the flower-stalk into 

 the wood and attacks the shoots. Trees which have suffered 

 from Blossom- Wilt may be recognised by the brown, withered 

 leaves which usually remain attached instead of falling off. 



The damage caused by Blossom-Wilt is in certain seasons 

 very serious. The factors chiefly contributing to an epidemic 

 attack are a low temperature, and a very moist atmosphere 



All the photographe used in this leaflet are by Dr. Wormald, and 

 Figs. 2, 3 and 4 are reproduced from the Annals of Applied Biology, 

 Vol. V, by kind permission of Dr. Wormald and the Cambridge Un : ver- 

 sity Prese. 



