Final diagnosis


Microdochium panattonianum (Marssonina panattoniana, anthracnose)

The outer leaves of these salads are strewn with spots, the core tissues of which eventually decompose and fall off. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
The spots may be distributed over the entire leaf blade; in general, they tend to be located at the base of the limbus. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
<b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole") causes greasy to orange spots on lower leaves. When they are numerous and confluent, their damage can be confused with that of the agents of basal rots.
Circular, moist, orange-colored spots characterize the early attacks of anthracnose ("shot-hole") on the leaf blade of lettuce. <b> <i> Microdochium panattonianum </i> </b>
When conditions are wet, the spots take on a rusty brown tint. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
<b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole") is particularly aggressive on the veins of salads. Several canker lesions, elongated and concave, illustrate it well on this lettuce leaf.
In some situations, large areas of the limbus are damaged. This is due to the large number of spots and the fact that they merge in humid conditions. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
The spots are more elongated on the veins and slightly concave. In some cases, we are dealing with real small elliptical and orange cankers. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
Ultimately, the spots give rise to holes and the limbus takes on a more or less screened appearance. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
In general, the spots lighten in their center; the tissues quickly necrode, split and fall off. Eventually, many holes dot the leaves giving them a riddled appearance hence the Anglo-Saxon name of the disease "Shot-hole". <b> <i> Microdochium panattonianum </i> </b> (anthracnose)
The spots on the leaves can split quite quickly. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
Acervule (or sporodochia) of <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole") as seen in necrotic leaf tissue.
Discrete fruiting bodies of the fungus, the acervuli, form on the spots. They are made up of very many conidiophores grouped together; these generate hyaline, bicellular, cylindrical and slightly curved conidia. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
The conidiophores observable in the acervuli are smooth and hyaline, sometimes septate; they show a narrowing in the conidiogenic region. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")
Numerous spindle-shaped and hyaline conidia are produced at the end of the conidiophores. They are usually bicellular when mature, slightly curved and show constriction at the septum. The length varies from 5 to 17 µm. <b> <i> Microdochium panattonianum </i> </b> (anthracnose, "shot-hole")