DISEASES OF CULTIVATED PLANTS 375 
is formed. There is great danger of separation of the bark layer from the wood 
at that time as at others. The sun exposed side seemed to have suffered worse 
by reason of the more extreme temperature changes which were incited on these 
exposures. Itis evident that warm periods in winter are a source of danger 
when followed by low tem- 
peratures. 
Upon very large trunks 
near the base, as on 
Grimes and some others, 
this may be the real ex- 
planation of frequent sun- 
scald or basal injuries. 
Wherever such an injury 
begins there is risk of the 
intrusion of wound fungi 
with all the consequences 
which follow their en- 
trance. The handling of 
winter injuries Must so far 
as prevention goes precede 
the conditions which cause 
it. Where possible the pre- 
vention of excessive late 
growth is desirable. In 
cases of orchard trees it 
may be that mulches of 
coarse litter, especially, 
will prove serviceable. It 
may be added that this 
injury to woody growths is 
a less developed phase of 
the killing back of herbac- 
eous plants by the prema- 
ture frosts. 
Another phase still is A 
ag gk Fig, 33. Johnathan tree, 4 years old, Southeastern test farm, 
the killing back of branch- Carpenter, in cultivated portion. Tree of vigorous previous 
es at the tips of woody growth with small lesion near base of trunk caused by freezing 
growth which are not and sprouts from below. Photographed July 20, 1908. From 
strictly hardy in our cli- Bulletin 192. 
mate. In the case of our : 
Japanese plum and of some ornamental shrubs, this is a frequent phenomenon 
and its cause is to be sought in the same factors above described. Growth being 
protracted late inthe season, these water gorged terminal twigs are killed 
by the subsequent winter freezing whenever this is severe. 
APRICOT 
The apricot is rarely planted though occasionally is set in our Lake 
Districts. The chief difficulties there have been the tendency to kill back.in 
winter. Apricot foliage in addition is liable to be attacked by the similar leaf 
parasites of peach and plum. 
