Final diagnosis


Podosphaera xanthii and Golovinomyces cichoracearum (Oïdium)

A few circular spots, powdery and whitish, gradually spread over this melon leaf. <b> <i> Podosphaera xanthii </i> </b> or <i> <b> Golovinomyces cichoracearum </b> </i> (powdery mildew)
Appearance of a young mycelial colony of <i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i> growing on a melon leaf. (powdery mildew)
Numerous powdery whitish spots now cover a good part of the lamina, some of them have coalesced in places. <i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i> (powdery mildew)
<i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i> have totally colonized this melon leaf whose photosynthetic activity is very disturbed. (powdery mildew)
<b><i>Sphaerothecae fuliginea</i></b> on melon
Powdery mildew can sometimes be expressed differently in the form of yellow, diffuse spots visible on the upper side of this melon leaf. <i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i>
Under the leaves with yellow spots, there is a discreet white down at their location. <i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i> (powdery mildew)
<i><b>Podosphaera fuliginea</b></i> (<i>Sphaerotheca fuliginea</i>, powdery mildew) on melon
This branch is entirely covered by one of the fungi responsible for melon powdery mildew, which sporulates heavily on the latter. <i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i>
Following a severe attack of powdery mildew, some leaves became necrotic and withered; the branches strongly colonized by the mycelium of the responsible fungus are superficially suberized. <i> <b> Podosphaera xanthii </b> </i> </b> or <i> <b> Golovinomyces cichoracearum </b> </i>
Young colonies of powdery mildew growing on a melon fruit as a white powdery spot. <i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i> (powdery mildew)
<b><i>Podosphaera xanthii</i></b> (Powdery mildew)
Observation with a binocular magnifying glass of the mycelial colonies of the 2 fungi responsible for powdery mildew makes it possible to observe their conidiophores at the end of which chain conidia are formed. <i> <b> Podosphaera xanthii </b> </i> or <i> <b> Golovinomyces cichoracearum </b> </i>
<i><b>Podosphaera fuliginea</b></i> on cucurbits
Three short-chain conidia formed at the end of a short conidiophore of <i> <b> Podosphaera xanthii </b> </i>. (powdery mildew)
Several cleistothecia, organs of sexual reproduction in oidiums, have formed on this leaf. <b> <i> Podosphaera xanthii </i> </b> (powdery mildew)
Detail of a cleistothecium of <i> Podosphaera xanthii </i> </b> observed under a light microscope. We can clearly see the brown wall of the latter. (powdery mildew)
<b> Cleistothecium </b> melon powdery mildew