456 
tony patches in wounds and, by delaying 
the healing over process, makes a favor- 
able place for the entrance of a parasitic 
fungus. 
Amongst the fungi which are re- 
sponsible for cankers in various parts of 
the country are: Bitter Rot fungus 
(Sphaeropsis malorum Pk.), Uyxosporium 
corticolum, Edg., Coryneum folicolum, 
Fekl., Phoma mali, Schulz and Sacc., 
Cytospora Sp., European Apple Canker 
(Nectria ditissima, Tul.) and Nummu- 
laria discreta Tul. 
Closely associated with canker caused 
by fungi is the killing back of small 
branches and twigs caused by the same 
organisms. In searching orchards for 
cankers we have found this dying back 
of the branches and water-sprouts much 
the more common of the two. The 
fruiting bodies of the same fungi have 
been found on both, and cankers on 
larger limbs have been found repeatedly 
which apparently started from the dis- 
ease following back on a smaller branch 
or twig. Inoculations with canker pro- 
ducing fungi early in the spring show 
that they are capable of killing the 
voung twigs very rapidly and run back 
a considerable distance in a single sea- 
son. A twig blight may be caused by 
the pear blight bacillus. 
In many ways the dying back of small 
branches is like the development of 
canker. The fungus may spread back 
only a short distance each year for a 
number of years or the spread is rapid 
and the branch is killed back a consid- 
erable distance in a single year. It is 
probable that in many instances the 
young wood is injured by freezing and 
the fungi gain entrance in this way. We 
have observed the same thing where 
young nursery stock has become in- 
fected through wounds made in cutting 
back when set. Twigs and limbs affected 
in this way should be cut off well below 
the diseased portion and the wounds 
protected from further infection. 
Sphaeropsis Canker 
The canker caused by the black rot 
fungus, Sphaeropsis malorum Pk., is 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
widely distributed. This disease is 
known as the “New Yo.k Apple Tree 
Canker,” because it was first described 
from New York. This fungus causes 
the black rot of the fruit and a lea 
spot as well as the disease of the wood. 
see Black Rot. 
The fungus attacks either young or 
old branches and the amount of damage 
depends on the amount of bark ang 
adjoining surface portions of the wooq 
which is destroyed. In some cases a 
branch may be girdled in a short time 
and death of that branch results, but in 
other cases the canker spreads for years 
on one side of the branch before it is 
completely girdled. The other side of 
the branch in such a case may become 
somewhat enlarged. 
To control this canker, the orchardist 
should remove all dead branches, and 
all old neglected trees such as one fre- 
quently sees along the roads, and burn 
them. Branches which show bad cankers 
should be cut off back of the canker and 
burned. In the case of young cankers, 
the branch can frequently be saved by 
cutting away the diseased tissue down 
to healthy wood, disinfecting with a 
solution of copper sulphate, one ounce 
to one gallon of water, or corrosive sub- 
limate, one part to 1,000 of water, and 
then painting over with pure white lead 
in boiled linseed oil or coating with a 
good quality of grafting wax. The trees 
should be gone over carefully a number 
of times each year and _ developing 
cankers and wounds should receive at- 
tention. Spraying tor apple scab will 
help to control the cankers by reducing 
the amount of material for infection and 
by covering wounds with the fungicide. 
All decayed fruit should be destroyed, 
since the black rot of the fruit and this 
canker are caused by the same fungus. 
The treatment outlined should go far 
toward controlling cankers caused by 
other fungi. 
Bitter Rot Canker 
This canker is caused by the fungus 
which causes bitter rot of the fruit. On 
the dead bark the fungus produces little 
black pustules from which, when they 
