152 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
leave enough of their wood bare to affect the cropping power of the 
un tipped trees to a slight extent. It is of course a more serious matter 
with bush trees, where the total length of bearing wood is limited, than 
with standards, where a concentrated crop is less important. It may 
be expected that our tipped trees of the three varieties named above, 
when they come into full cropping, will, apart from other causes, be 
capable of producing more fruit on a tree of equal size than the un- 
tipped trees, simply because their branches are better furnished with 
spurs. 
7. Effect on Susceptibility to Certain Diseases. 
Since the sixth year after planting (1918 and 1919), it has been 
evident that the tipped and spurred trees are far less affected by certain 
fungus diseases than the untipped trees. The more important of 
these diseases are : Apple Scab or Black Spot (Venturia inaequalis), 
Apple Mildew (Podosphaera leucotricha) , and Common Canker (Nectria 
ditissima). The percentage of fruit of the unpruned and long-spur 
pruned trees attacked by Scab is shown for certain varieties in Table V. 
It should be noted that the fruits recorded as " scabbed " usually 
include a good many not badly enough affected to be appreciably 
reduced in market value. All that show a recognizable infection, 
however slight, are included. 
Table V. — Percentage of Fruit attacked by Scab. 
1919. 
1920. 
192 
1. 
Unpruned. 
Long- spur 
Pruned. 
Unpruned. 
Long- spur 
Pruned. 
Unpruned. 
Long- spur 
Pruned. 
Allington 
30 
2 
82 
54 
I 
I 
Bismarck 
69 
No fruit 
44 
42 
3 
O 
Cox's Orange 
34 
0 
(32) 
(33) 
6 
4 
James Grieve (Crab) 
46 
3 
31 
14 
17 
5 
(Paradise) 
43 
0 
56 
21 
10 
2 
Newton Wonder 
59 
9 
33 
36 
9 
3 
Worcester P. (Crab) 
37 
34 
66 
44 
14 
3 
(Paradise) 
70 
22 
38 
7 
13 
1 
Rival . 
6 
2 
Average . 
45 
10 
48 
3i 
9 
2 
The difference in favour of the long-spur pruned trees is so great 
and so uniform that there is clearly a very considerable effect from 
pruning. There are but two cases — ' Newton Wonder 1 and ' Cox's 
Orange ' in 1920 — where the proportion of scabbed fruit was greater 
on the long-spur pruned trees, and of these, one case (' Cox's ') is doubt- 
ful, since there were very few fruits on any of the trees. 
It has been suggested that the difference is mainly or entirely due to 
the cutting out of centres of infection in the pruning. This no doubt has 
in some cases a good deal of effect, but only in the case of those 
