http://www.hortnet.co.nz/publications/hortfacts/hf205001.htm
Black spot (Venturia inaequalis) is a fungal disease of apples, often referred to as apple scab outside of New Zealand. Apple black spot is a different fungus to pear black spot, and both are different to black spot on roses.



Venturia inaequalis anamorphs have been described under the names Fusicladium dendriticum and Spilocaea pomi. Whether V. inaequalis is a single species or contains several cryptic species has been a matter of debate for a long time. Recent genetic studies have revealed a considerable uniformity of the species. In addition, the fungus Spilocaea pyracanthae, a parasite of Pyracantha appeared not to genetically differ from V. inaequalis, being thus a special form of the latter.

[edit] MorphologyThe fruiting bodies, ascocarps appear in the form of pseudothecia. They are solitary and embedded into the host plant tissue. A pseudothecium has small dark hairs around its opening, and contains pseudoparaphyses along with asci. The asci contain eight haploid ascospores. The haploid chromosome number of V. inaequalis is seven.



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Note added at 14 hrs (2011-03-12 14:00:58 GMT)
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ll a enfermedad más importante que ataca al
manzano actualmente en Navarra es el
moteado. El incremento de la misma quizás se
deba esencialmente a la mayor sensibilidad de
las variedades que hoy día se cultivan, pero
considerando también que en los últimos años se están
dando condiciones climáticas favorables para su
desarrollo, sobre todo en las primeras fases del ciclo
vegetativo.
Esta enfermedad es provocada por el hongo Venturia
inaequalis. Este produce sus ascosporas en la primavera
en cuerpos fructíferos denominados pseudotecios
creados durante el invierno en las hojas caídas en el
suelo y en los denominados conidios, sobre los tejidos
verdes atacados durante la temporada vegetativa.
Aunque su acción sobre las hojas pueda mermar los
rendimientos, el daño más grave se produce cuando
ataca al fruto, al afectar a su desarrollo, a su calidad, a
su capacidad de conservación en cámara y por lo
tanto a su rentabilidad.

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Note added at 1 day15 hrs (2011-03-13 15:09:24 GMT)
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Perdón, pensé que el hongo venturia inaequalis, que provoca el moteado en las manzanas, era el mismo para las peras, pero no. Para las peras es el venturia pirina.
http://www.caf.wvu.edu/kearneysville/disease_descriptions/om...

Pear Scab
Venturia pirina



I. Introduction: Pear scab is an economically important disease throughout the world and can cause serious losses on susceptible cultivars. The disease is more of a problem in European countries than in North America, and is especially of major concern in Japan. Sometimes called black spot, pear scab resembles apple scab (Venturia inaequalis) in nearly all respects, and is caused by the closely related fungus, V. pirina. Pear cultivars differ in susceptibility to scab; however, cultivars resistant in one region of the country may not be resistant in another region.

II. Symptoms: Symptoms of pear scab are very similar to apple scab. Lesions on leaves and petioles begin as round, brownish spots that eventually become velvety in appearance. Within these lesions conidia are produced. Later in the season, small spots can be observed on the lower surface of the leaves. These are usually the result of late spring or early summer infections. Leaf infection of pear is not as common as apple scab on apple leaves.

III. Disease Cycle: Scab lesions on fruit occur on the calyx end and eventually on the sides of the fruit (photo 2-45). As these lesions enlarge, they become dark brown and form large black areas as they coalesce. Lesions on immature fruit are small, circular, velvety spots. Darker, pinpoint spots develop as the fruit matures. Infected fruit often become irregular in shape.

Unlike apple scab, twig infections are common with pear scab. Early in the growing season, lesions on young shoots appear as brown, velvety spots. Later, these lesions become corky, canker-like areas. The following spring, pustules will develop within these overwintered lesions. These pustules produce spores (conidia) that perpetuate the spread of the disease.


http://articulos.infojardin.com/Frutales/enfermedades-frutal...

Enfermedades en árboles frutales de hueso y de pepita

1. Oidio o Cenizo en Frutales
2. Roya del peral (Gymnosporangium sabinae)
3. Cribado o Perdigonada (Clasterosporium carpophilum)
4. Lepra del melocotonero o Abolladura (Taphrina deformans)
5. Monilia o Momificado (Monilia sp.)
6. Fusicocum
7. Mal del plomo
8. Roña o Moteado de manzanas y peras (Venturia spp.)
9. Moteado del níspero (Fusicladium eriobotryae)
10. Septoriasis del peral (Septoria piricola)
11. Fuego bacteriano o Chamuscado (Erwinia amylovora)
12. Bacteria Pseudomonas syringae
13. Podredumbre blanca de las raíces (Armillaria mellea y Rosellinia necatrix)
14. Negrilla
15. Tumores o Agallas del cuello (Agrobacterium tumefaciens)
16. Virosis de frutales
17. Virus de la Sarka