Fireblight

Question 1

Firelight - symptoms

Answer 1

Flowers - appear water soaked/grey green> turn brown/black. Entire clusters can be affected.
Shoots - on succulent shoots leaves and stems turn brown/black and bend into shepherd’s crook shape, in humid weather weather droplets of sticky bacterial ooze may be seen.
Stems - in warm humid conditions shoot blight infection will extend down the stem, expanding beyond current seasons’s growth and in to older wood.
Foliage - looks blackened and scorched.
Older wood - dark sunken cankers form, in spring wind summer during humid weather white ooze May exude from infected wood.
Beneath bark of if infected areas - tissues are stained reddish-brown.
Young fruit - small, dark and shrivelled.
Older fruit - expanding red, brown and black lesions, in warm and humid conditions this may exude bacterial droplets.
Rootstock - can be infected (rootstock blight) causing wilting and death of trees, M9 and M26 rootstock are particularly vulnerable.

Question 2

Fireblight - life cycle

Winter

Answer 2

Bacterial disease.
Infects plants through injuries and natural entry points eg flowers.
Bacteria overwinters in bark, at the edge of cankers formed during the previous growing season.

Question 3

Fireblight lifecycle

Spring

Answer 3

Primary inoculum
Bacteria that have overwintered at edge if cankers multiply, exude ooze to surface in sticky droplets > moved to blossoms by rain and insects.

Question 4

Fireblight lifecycle

Floral epiphytic phase

Answer 4

Bacterial disease.

Floral epiphytic phase - Temp over 18.3° C > bacteria on flower stigma multiplies and is moved from Flower to Flower by bees and rain. Pathogens can occur at high levels on stigma but generally need to be washed by rain into nectaries to cause infection

Question 5

Fireblight lifecycle

Floral infection

Answer 5

Primary infection stage
Once infected flowers die after 1 to 2 weeks.
Bacteria that oozes from them provides in inoculum for secondary spread to young succulent shoots.

Question 6

Fireblight lifecycle

Second phase

Answer 6

Second phase - spread to young, succulent shoots.
Bacteria moved to shoots by insect and rain - enters site through wounds caused by insect activity, wind damage and hail.
More ooze is exuded from these sites > furthering the spread of bacteria.
As growth slows and stops, shoots become less susceptible > advancement through woody tissue slows and cankers form.
Some cankers will overwinter (‘holdover’) to begin cycle next spring.

Question 7

Fireblight

Overwintering and rootstock

Answer 7

Overwintering cankers can also move internally from canker margins to nearby shoots. Shoots are infected systemically yellow/orange colour in shoots. (Canker blight)

Rootstock infection can develop on succulent suckers or from scion infection

Question 8

Name of bacterial cause

Answer 8

Erwinia amylovora