r)0 A " WitJier Tip" of Plum TrceR 



results it would seem that the youno; leaves also become infected from 

 the dead shoots under certain conditions not yet understood. In severe 

 attacks many of the leading shoots are killed and fruit-buds are replaced 

 by the weak "unripe" twio;s, that are induced to grow out. The diseased' 

 twigs should therefore wherever possible be removed from the trees 

 together with all rotting and mummied fruit. 



Some growers, at the time the fruit is gathered, encourage their 

 pickers to remove all the plums affected with "brown rot." If this 

 system became more general and could be extended to the pinching ofE 

 of all "withered tips" also, the amount of fruit destroyed each year by 

 "brown rot" would be reduced considerably. As an alternative the dead 

 twigs could be removed in winter when, as a rule, they are easily dis- 

 tinguished by the recurved apex and by the persistent withered leaves. 

 Where practicable they should be removed and burnt but in any case 

 they are far less dangerous on the ground than if left on the tree. To 

 test this point thirty-nine withered tips were removed from three trees 

 and placed on the ground under the trees in September 1916; when 

 examined in the spring of 1917 five of them only had pustules of the 

 fungus, whereas of those left on the trees all, with very few exceptions, 

 produced pustules. 



As in the case of the " Blossom Wilt " disease of apple trees spraying 

 with ordinary fungicides is not likely to prove nearly so efficacious as 

 the removal of the dead twigs and diseased fruit. The stigmas of the 

 open flowers are liable to become infected and these cannot be covered 

 with a spray fluid without great risk of injury to the blossom. The fruit 

 becomes infected through wounds and therefore again spraying cannot 

 prove sufficiently protective. A spray that would kill the pustules or 

 render them sterile might be effective but since the diseased twigs are 

 very slender and often at the extreme tips of the branches great care 

 would be necessary during the application to cover them with the spray 

 and large quantities of the fluid would be wasted. 



Experiments however were carried out to ascertain the effect of 

 fungicides on the pustules liorno by diseased twigs, attention being con- 

 fined to preventing the pustules from shedding their conidia during that 

 period of the year when new infection occurred. Twigs bearing ])ulveru- 

 lent pustules were taken from the trees and atomized with the various 

 spray fluids, then placed in the open, that they might be subjected to 

 ordinary atmospheric conditions, and examined from time to time. 



It was found that the commonly employed fungicides such as 

 Bordeaux Mixture, soda Bordeaux ("Burgundy" Mixture), cuprani, eau 



