Agriculture Reference
In-Depth Information
bining
T. viride
inoculation with a tecnobucazole seed treatment (Clarkson
et al.
,
2006). It may be that biological control agents, disease-suppressive composts
and fungicidal seed treatments can be combined to give improved control of
white rot in future.
Basic information on the most important fungal diseases of stored bulbs is
summarized in Table 5.7. The information in this section is largely drawn from
Maude (1990b), Snowdon (1991) and Mohan and Schwartz (2008).
Sometimes, some of the pathogens discussed under soil-borne fungal diseases
do not manifest as disease until they cause rots in stored bulbs. These include: (i)
Fusarium oxysporum
, which can cause watery softening advancing from the base
of the bulb, sometimes with a pink tinge; (ii
) Sclerotium rolfsii
, where infections late
Table 5.7.
Main fungal diseases of the stored bulbs of allium vegetables.
Temperatures:
Characteristic
Infection
range;
Disease
a
Pathogen
Host crops
b
symptoms
sources
optimum (°C)
Neck rot (see
Botrytis aclada
;
O, s, g, l
Bulb decay
Spores from
5-25; 22-23
Plates 2, 9a
B. allii
;
B.
starting at
senescent
and 9b)
byssoidea
bulb neck,
leaves and
forming black
from sclerotia;
sclerotia on
infected seed
bulb surface
Black mould
Aspergillus niger
O
Black, sooty
Debris in soil;
10-40; 28-34
(see Plate 9c)
mould on and
infected seed
between outer
bulb scales,
particularly
along veins
Blue mould
Penicillium
spp.
O, g
Soft, watery
Debris in soil
15-32; 21-25
lesions later
covered with
blue mould
Smudge (see
Colletotrichum
O, s, l
Black, bristled
Spores
10-32; 13-25
Plates 2 and 9d)
circinans
spots on
splashed
surface of
from
white-skinned
infected
bulbs
debris in soil
a
The diseases are listed in order of importance.
b
O, onion; s, shallot; g, garlic; l, leek.
