''Septoria cucurbitacearum'' is a

fungal A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the tradit ...

plant pathogen infecting cucurbits. Symptoms of Septoria leaf spot are similar on all the cucurbits infected.

Description

Spots are normally circular or occasionally irregular, beige to nearly white in color, measuring 1 to 2 mm in diameter or occasionally larger on the upper leaf surface. A narrow brown border surrounds the spot and, with age, the lesion may crack. When the disease first appears in the spring under moist conditions, the spots appear with or without a white speck surrounded by a much larger brown water-soaked border, giving the appearance of a different disease. The distinguishing sign on older spots is the presence of small, black, speck-like fruiting bodies called

pycnidia A pycnidium (plural pycnidia) is an asexual fruiting body produced by mitosporic fungi, for instance in the order Sphaeropsidales ( Deuteromycota, Coelomycetes) or order Pleosporales (Ascomycota, Dothideomycetes). It is often spherical or inve ...

embedded within the tissue. Not all spots will contain

, but some may contain up to eight or more. The black specks can be seen with an unaided eye. Under moist conditions, long, thin, needle-like

conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

are released. Small (1 to 2 mm) erumpent whitish spots appear as a rash on the surface of infected Butternut and

Pumpkin A pumpkin is a cultivar, cultivated winter squash in the genus ''Cucurbita''. The term is most commonly applied to round, orange-colored squash varieties, but does not possess a scientific definition. It may be used in reference to many dif ...

fruit.

Pycnidia A pycnidium (plural pycnidia) is an asexual fruiting body produced by mitosporic fungi, for instance in the order Sphaeropsidales ( Deuteromycota, Coelomycetes) or order Pleosporales (Ascomycota, Dothideomycetes). It is often spherical or inve ...

Septoria ''Septoria'' is a genus of fungal plant pathogens in the phylum Ascomycota. They cause necrotic leaf spots on the leaves of their hosts, producing filiform or cylindrical conidia inside pycnidia embedded in the leaves. Economically important spe ...

are not often found on these whitish spots, but other organisms including Cucurbit Anthracnose ('' Colletotrichum orbiculare'') and Black dot (''

Colletotrichum coccodes ''Colletotrichum coccodes'' is a plant pathogen, which causes anthracnose on tomato and black dot disease of potato. Fungi survive on crop debris and disease emergence is favored by warm temperatures and wet weather. Hosts and symptoms ''C. co ...

'') sometimes invade these lesions.

References

External links

Index Fungorum

USDA ARS Fungal Database
cucurbitacearum Fungal fruit diseases Vegetable diseases Fungi described in 1876 Fungus species {{fungus-fruit-disease-stub