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Ministry of Agriculture, Food and Rural Affairs

Fabraea Leaf Spot

Leaf lesions start as small, purple to black pinpoint spots. Lesions on leaves and petioles are small, circular, purple to black spots. Larger lesions on fruit can cause it to crack. Fabraea lesions on leaves. Lesions may coalesce on severely affected leaves Bosc pear fruit with a few Fabraea lesions Fabraea can cause trees to lose leaves before harves Severely infected Seckel fruit
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Beginner

This pest affects:

Pear

Scientific Name
Fabraea maculata

Identification
Petioles & leaves

  • Lesions occur on upper and lower leaf surface
  • Lesions are initially tiny, round, purplish-black spots, which quickly enlarge to 0.3 to 0.6 cm in diameter and usually have a blackish-brown center
  • Spots coalesce and severely infected leaves fall to the ground prematurely

Fruit

  • Lesions are larger than those on leaves, black, slightly sunken
  • May cause the fruit to crack and drop

Shoots

  • Lesions on current season's shoots are small inconspicuous, purplish-black spots
  • Some lesions develop into superficial cankers, but most are walled-off during the next growing season, so that cankers rarely persist in two-year-old wood

Often Confused With
Pear Scab – brown or olive green lesions with distinct margins developing on underside of leaves first. No creamy, gelatinous mass of spores ooze from the lesion when wet.

Spray burnno creamy gelatinous mass of spores

Similar leaf spots can be caused by many other fungi or by phytotoxocity from pesticide sprays. Therefore, the only way to determine if leaf spots are actually caused by Fabraea is to check under a microscope to determine if Fabraea conidia are present in the leaf spots. Fabraea produces distinctive four-celled conidia with two hair-like setae that make the conidia look like microscopic insects.

Period of Activity
Ascospores from last year's leaf litter can mature anytime from mid-May through early July.  Often the first infections do not occur until mid-June to early July. Secondary infections begin about 1 month later and reoccur throughout the season during periods of rain. Fabraea epidemics are usually reported in early July when the disease suddenly "explodes" in certain blocks.

Scouting Notes
At midseason, examine 20 of the lowest leaves on each sample tree for earliest symptoms.

Bosc and Seckel are more susceptible than Bartlett.

Threshold
There are no fungicides registered for Fabraea leaf spot.  Cultural control should be initiated after leaf drop or before bud break.

Photo source:

Advanced

This pest affects:

Scientific Name
Fabraea maculata

Identification
Petioles & leaves

  • Lesions occur on upper and lower leaf surface
  • Lesions are initially tiny, round, purplish-black spots, which quickly enlarge to 0.3 to 0.6 cm in diameter and usually have a blackish-brown center
  • Spots coalesce and severely infected leaves fall to the ground prematurely
  • A small black acervulus may develop in the center of each lesion, from which conidia ooze in a creamy, white mass in wet weather

Fruit

  • Lesions are larger than those on leaves, black, slightly sunken
  • May cause the fruit to crack and drop

Shoots

  • Lesions on current season's shoots are small inconspicuous, purplish-black spots
  • Some lesions develop into superficial cankers, but most are walled-off during the next growing season, so that cankers rarely persist in two-year-old wood

Often Confused With
Pear Scab – brown or olive green lesions with distinct margins developing on underside of leaves first. No creamy, gelatinous mass of spores ooze from the lesion when wet.

Spray burnno creamy gelatinous mass of spores

Similar leaf spots can be caused by many other fungi or by phytotoxocity from pesticide sprays. Therefore, the only way to determine if leaf spots are actually caused by Fabraea is to check under a microscope to determine if Fabraea conidia are present in the leaf spots. Fabraea produces distinctive four-celled conidia with two hair-like setae that make the conidia look like microscopic insects.

Biology
Most pear and quince varieties are susceptible to Fabraea leaf spot, but Bosc and Seckel are the most susceptible of the commonly grown cultivars.  Apple and hawthorn leaves can be infected.

The disease overwinters on leaves and in superficial twig cankers. Ascospores formed in apothecia in the leaves on the orchard floor and conidia formed in acervuli in cankers on shoots are the sources of primary inoculum. Spores are dislodged and spread by rain splash.  Wetting periods for infection may vary from 8 to 12 hours at temperatures of 10-25°C. Each leaf spot produces millions of slimy conidia that are disseminated by splashing rain or by rust mites, pear psylla, or other insects. A minimum of eight hours of wetting are required for infection. If spores are disseminated by insects, infection can occur during long dew periods in the absence of rain.

Lesions begin to appear about 7 days after the beginning of an infection period. The disease may advance rapidly in late summer as wind and rain distribute the conidia throughout the tree.  

Fabraea leaf spot can build up more quickly than pear scab because older leaves and fruit never become resistant to infection by Fabraea. Leaves and fruit on quince and pear trees remain susceptible to Fabraea leaf spot right up until harvest. Thus, when Fabraea leaf spot epidemics develop in early summer, all of the existing leaves can become infected in a short time if inoculum is present and trees are left unprotected.
If the disease is not controlled, pear trees can become defoliated in a few weeks. Severe defoliation can substantially reduce tree vigour and yield, especially if trees are defoliated several years in a row.  The disease can kill large limbs and even entire trees. Where the disease is severe, fruit become severely spotted and are unmarketable.

Period of Activity
Ascospores from last year's leaf litter can mature anytime from mid-May through early July.  Often the first infections do not occur until mid-June to early July. Secondary infections begin about 1 month later and reoccur throughout the season during periods of rain. Fabraea epidemics are usually reported in early July when the disease suddenly "explodes" in certain blocks.

Scouting Notes
At midseason, examine 20 of the lowest leaves on each sample tree for earliest symptoms.

Bosc and Seckel are more susceptible than Bartlett.

Threshold
There are no fungicides registered for Fabraea leaf spot.  Cultural control should be initiated after leaf drop or before bud break.

Management Notes
Mow fallen leaves and apply urea to leaves just before leaf fall or before bud break in the spring to speed up the decomposition process and reduce inoculum.

Control pear psylla and rust mite as they can help spread Fabraea leaf spot during the summer.

There are no fungicides registered for Fabraea leaf spot control. Some fungicides used to control pear scab help suppress this disease. In blocks with a history of Fabraea leaf spot, maintain fungicide coverage in pear blocks throughout June and early July.

Some information included above excerpted from;

Photo source: