3 1 8 W or maid. — Further Studies of the ‘ Brown Rot ’ Fungi . I. 
they are not found on the bark of the shoots (or on the cankers) until the 
following winter. 1 
€ 
VI. The Economic Importance and the Control of 
the Disease. 
No estimates have yet been obtained as to the losses due to Shoot- 
Wilt, but the direct damage caused by the disease is probably inappreciable 
except in certain seasons when there is mild damp weather as the leaf-buds 
are unfolding. The short shoots are, as already explained, incipient fruit 
spurs, and the killing of a number of such shoots one year means a corre- 
sponding reduction in the number of inflorescences the following year 
(Fig. 6). The fact that further extension of the mycelium often ceases 
before the cankers girdle the twigs is of some significance, since such lesions 
tend to become healed over, so that little direct harm is done in those cases 
unless many shoots become infected. 
Perhaps the chief economic importance of the disease is the fact that 
not only may the mycelium in the withered leaves give rise to the Monilia 
fructifications during the season in which infection occurs and so cause 
further dissemination of conidia that year, but the dead shoots and cankers 
become, in the following season, sources of infection which are easily over- 
looked. When it is remembered that Sclerotinia cinerea infects not only 
the leaves (as shown in this article) but also the flowers (often causing 
serious outbreaks of Blossom-Wilt) and the fruit, all possible sources of 
infection must be taken into consideration if attempts to keep the Brown 
Rot diseases under control are to be successful. 
The cankers on the one-year-old twigs are too small for their excision 
to be a practical operation, and to cut back behind them would often mean 
removing a number of incipient fruit spurs. It cannot be over-emphasized 
that mummied fruit and twigs killed by the Brown Rot fungi should be 
removed and destroyed by fire whenever this is at all practicable. To 
supplement this treatment the writer recommends, in cases where the 
‘ Shoot-Wilt ’ disease is known to be present, the application, in winter, of 
a caustic alkali wash to which soap has been added, the soap being necessary 
to ensure a complete wetting of the powdery Monilia fructifications. Such 
a wash has not yet been thoroughly tested as a means of controlling Brown 
Rot diseases, but it has been found, in experiments on a small scale, that 
a spray-fluid containing i per cent, caustic soda and i per cent, soft soap, 
used as a winter wash shortly before the buds open, will either destroy the 
fructifications or render them sterile for some weeks. 
1 The writer has found Monilia fructifications on the bark of a recently killed plum shoot on 
one occasion only — on a shoot affected with ‘ Wither-Tip’ in May 1921. 
