Agriculture Reference
In-Depth Information
Irregular-shaped lesions develop in the bark, which looks moist, soft and rather
spongy. When the affected bark is cut the tissue is orange-brown with lighter
and darker brown striped areas. The pathogen is soil-borne and its spores are
dispersed by splashing.
The lesions can girdle and kill the tree if not checked by being cut out at an
early stage and the wounds so made treated with a copper fungicide.
Rootstocks differ greatly in their resistance. 'B.
' is very resistant, 'M.
',
'MM.
' and 'Robusta
' are resistant, but 'MM.
' is susceptible (Cummins
and Aldwinkle,
). Several new rootstock clones from
Cornell and East Malling are also resistant (Robinson
et al.
,
; Janick
et al.
,
; Webster
et al.
,
). Scion cultivars are generally much less tolerant than the resistant
rootstocks, so high-working on such rootstocks, so that the scionwood is out of
the soil and splash zone, is an important control measure.
P. syringae
also can
cause fruit rotting.
Storage rots
A number of other fungi cause rots in store. These include
Pezicula
(
Gloeo-
sporium
) spp.,
Alternaria alternata
,
Penicillium
spp.,
Botrytis cinerea
,
Monilia fructigena
and
Mucor piriformis
. Control focuses on several areas. Appropriate orchard
management, including effective spray programmes, lowers the load of inocu-
lum. Reduction in injuries to fruit through rough handling can greatly reduce
post-harvest decay: Benic and Combrink (
% of the decay in
apples was due to infections resulting from mechanical injuries. Maintenance
of high sanitary standards in packing-houses is essential to avoid fungal inocu-
lum from decaying fruit, etc. being carried over from one season to another
and within a season. Rapid fruit cooling to below
) reported
◦
C greatly slows down
fungal growth. Chemical treatment, e.g. benomyl just before picking or in post-
harvest dips greatly reduces, for example,
Gloeosporium
damage (Burchill and
Edney,
). High fruit Ca status increases resistance to
Gloeosporium. '
Cox'
and 'Ingrid Marie' apples are very susceptible, 'Jonathan' and 'Jonared' very
resistant and 'Golden Delicious' resistant (Alston,
).
In Japan,
Alternaria alternata
is also an important pathogen as a result of
causing black spot disease of Nashi pears. The cvs. 'Kosui' and 'Hosui' are
resistant to this (Kajiura,
).
Apple bitter rot caused by
Glomerella cingulata
is a very important fungal
disease in Brazil, being potentially very serious wherever high temperature
and high humidity (
◦
C and
% RH) occur simultaneously. 'Fuji',
'Delicious', 'Golden Delicious', 'Granny Smith' and 'Gala' are susceptible and
'Jonathan' and 'Red Rome' fairly resistant. Some potential parental material
including
M
-
.
×
zumi
,
M. prunifolia
and
M
.
×
purpurea
clones is highly resistant
(Camilo
et al.
,
).
