CHE REFERENCE LIBRARY - Pole Shift Survival Information

196 THE NURSERY-MANUAL
ga.11 infections call be reduced by using a root and cion of approximately
the same size and by wrapping the grafts carefully.
APPLE- AXD ~UPSC,~B. - The scab diseases exist apparently
in every country where apples and pears are grown commercially.
In the nursery, the pearscab
is usually of importance
only on the Flemish
Beauty buds. The applescab
is most destructive
in the nursery on the varieties
McIntosh, Transcendent
and Martha.
Lkmipt~ion .-The leaves
and the fruit and sometimes
the twigs are affected.
The disease appears on
the leaves as olivaceous
to dark brown or nearly
black spots (Fig. 212).
There is a tendency for
the lesions to extend along
the veins of the leaf, making
them irregular in ap-
FIQ. 212. Scab on apple leaves. pearance.
Cmcsc. - The scab
lesions are caused by the fungi Tk~Wia ilLceqlraZis and V~turia
pyrinn, which produce a large number of spores in the spots.
The spores are disseminated by wind and rain and are responsible
for the new infections which occur throughout the summer.
On the diseased leaves that fall to the ground in autumn,
special fruiting bodies (perithecia) of the fungi are produced
and by this means the organism lives over winter. In spring
the perithecia produce spores which attack the new foliage.