Ramularia leaf spot fungi
What are they?
Species of Ramularia fungi cause disease
in many plants, including: wheat, barley,
cotton and oats. Ramularia fungi are found
all around the world, from Europe to South
America and New Zealand. In Scotland
the barley crop can be badly affected by
Ramularia, causing losses of £10M every
year.
These patches mean there is less leaf area
to absorb sunlight for photosynthesis, and
so plants produce less sugar, grow less and
produce a smaller grain harvest.
Image 3: Ramularia rubella on a leaf of a dock plant. Courtesy of Tristram
Brelstaff, Wikimedia.
Image 1: Barley field. Credit: the United States Department of Agriculture.
How do they infect?
Ramularia fungal spores attach onto leaves.
When there is moisture, such as morning
dew, the fungal spores start growing long
tubes called hyphae.
These tentacle-like hyphae enter the plant
through pores on the leaf surface called
stomata.
Image 4: Ramularia centaureae. Credit: James Lindsey’s Ecology of
Commanster Site.
How are they spread?
Ramularia fungal spores are airborne and are
released from Ramularia fungi on infected
leaves. The spores then spread to leaves on
the same plant or to nearby plants.
If infected seeds are sown; Ramularia
can spread around a field or to new areas.
Infected seeds make harvest less profitable.
Image 2: Ramularia collo-cygni asexual spore. Credit: B. Sutton and J.M. Waller,
Trans Brit Mycol Soc 90 (1): 57 (1988).
Once inside the plant, the hyphae tubes
push in-between plant cells and feed off
nutrients in the leaf. Ramularia can also
produce toxins, which are activated by
sunlight and cause plant cells to die. Dead
cells create large dark spots on leaves.
Image 5: Ramularia didyma asexual spore. Credit: Cesar Calderon, USDA APHIS
PPQ, Bugwood.org.
What are the symptoms?
The first visible symptoms are small brown
spots, surrounded by a yellow halo on the
leaf surface. Later, neighbouring spots join
together to form large brown patches.
Image 5: Image of barley seeds. © Mimimilch, Dreamstime Stock Photos &
Stock Free Images
How does Ramularia
survive over winter?
Ramularia can infect neighbouring weeds
such as couch grass, and as the number of
spores increases on weeds, it’s easier for
the fungus to infect crop plants.
Did you know?
Ramularia fungi can grow at 4°C (the same
chilly temperature as your fridge). This
survival at cold temperatures allows the
Ramularia fungi to spread to areas with cold
climates.
Image 6: Couch grass (Elytrigia repens). Credit: Rasback, Wikimedia.
Spores can also survive on dead plant
material over winter. This makes it
particularly hard to stop a disease outbreak
the following spring.
Image 9: Ramularia anthrisci. Credit: James Lindsey’s Ecology of Commanster
Site.
What control is there?
The disease can be controlled by breeding
and growing plant varieties which are
resistant to Ramularia. Farmers can buy
seed, which is certified disease free.
Chemical fungicide sprays can be used.
However, these are only effective if sprayed
before the disease symptoms appear
otherwise the treatment does not work.
Image 7: Lite-Trac Crop Sprayer. Credit: Lite-Trac, Wikimedia.
Image 9: Ramularia cirsii. Credit: James Lindsey’s Ecology of Commanster Site.
Questions
1. Can you think of any food or drinks made
from barley?
2. Why do you think Ramularia causes lots
of damage in the UK?
3. Can you name a key disease symptom
caused by Ramularia?
4. The fungicide spray can only work if it’s
applied before disease symptoms appear.
Why is this a problem?
Created by...
Image 8: Barley. Credit: Jasmain, Wikimedia.
Created by the BSPP
(2014). More resources
available on the BSPP
site: www.bspp.org.uk.