Agriculture Reference
In-Depth Information
English name
Causal bacteria
Symptoms
Points of note
Sour skin or
Burkholderia cepacia
(formerly
Macerated, sour-smelling, mushy bulb
Checked by drying out of infected
bacterial
Pseudomonas cepacia
)
scales; grainy yellow ooze under
leaves and bulb necks; can persist in soil
canker (see
infected scales; spreads within,
Plate 5b)
rather than between, scales; on leaves,
lesions and leaf death
Bacterial streak
Pseudomonas viridiflava
(similar to
Dark, water-soaked streaks on leaves
Survives as surface dweller (epiphyte) on many
or bulb rot
P. syringae
)
spreading to leaf base and into bulb;
weeds; very destructive to N-rich succulent
causing total foliar collapse in severe
onions
cases; milder infections causing pale
yellow turning to red-brown rotten
centre bulb scales after harvest
Centre rot
Pantoea ananatis
(closely related to
Water-soaked, white-bleached centre
Pathogenic on several other crops including
Erwinia herbicola
- synonym
Pantoea
leaves surrounded by brown tissue;
pineapple; epiphytic on many weeds;
transmitted by thrips and seed-borne
1
agglomerans
)
macerated, foul-smelling bulb interior;
also infects seed stalks
Bacterial soft
Erwinia
sp. of the 'carotovora' group,
Soft yellow to brown rot starting in bulb
Short-lived in soil but persists in rhizosphere;
rot (see Plate 5a)
including
E. carotovora
ssp.
carotovora
,
centre releasing foetid-smelling, viscous,
survives in intestine of onion fly larvae and
E. chrysanthemi
,
E. herbicola
,
E. rhapontica
watery fluid
adults; infects most vegetable alliums
Slippery skin or
Burkholderia gladioli
pv.
alliicola
Rotten inner scales spreading to the
B. gladioli
pv.
alliicola
infects via wet neck
other soft rots
(formerly
Pseudomonas alliicola
or
whole bulb; the infected core can
wounds when onions topped at harvest; bulb
(see Plate 5c)
P. gladioli
pv.
alliicola
),
slip out of the top of the onion bulb
rot promoted by high-temperature drying
P. aeruginosa
,
P. marginalis
,
when squeezed, hence the name
(
c
. 30°C); can be spread by planting infected
sets
2
Lactobacillus
,
Enterobacter cloacae
'slippery skin'; some species also
