II.2. SQUASHES, PUMPKINS, ZUCCHINIS, GOURDS (CURCURBITA SPECIES) – 125
Choanephora cucurbitarum
This fungus causes a whisker-like fungal growth that causes blossoms and fruits to
rot. The disease is commonly referred to as blossom blight or wet rot (Agrios, 1997;
American Phytopathological Society, 2011; OMAFRA, 2011).
Erysiphe cichoracearum
E. cichoracearum causes a disease known as powdery mildew. Whitish, talcum-like,
powdery fungal growth develops on both upper and lower leaf surfaces and on petioles
and stems. Symptoms usually develop first on older leaves, on shaded lower leaves and
on upper leaf surface. Infected leaves usually die, and plants senesce prematurely
reducing photosynthesis, thereby reducing yield (Agrios, 1997; Jahn, Munger and
McCreight, 2002; American Phytopathological Society, 2011; OMAFRA, 2011).
Fusarium oxysporum
F. oxysporum is soil borne and causes a damping-off disease; i.e. it causes young
seedlings to wilt and die or not emerge at all. It is occasionally found in cucurbits
(Agrios, 1997; American Phytopathological Society, 2011; OMAFRA, 2011).
Phytophthora capsici
P. capcisi causes a blight resulting in leaf spots and fruit rot, seedling damping-off
and possible total crop loss. Stem and leaf petiole lesions appear as light to dark brown,
water-soaked and irregular in shape, eventually becoming dry, brittle and papery.
Older plants with root infections may suddenly wilt. In fruit, the symptoms begin as small
water-soaked lesions in the rind, which enlarge quickly and become a soft sunken area
covered with white fungal growth (Agrios, 1997; Lopez, Brune and Henz, 1999;
American Phytopathological Society, 2011; OMAFRA 2011).
Plectosporium tabacinum
P. tabacinum, also known as Microdochium tabinum, causes a blight characterised by
the production of light tan to “bleached” sunken, spindle-shaped lesions, primarily on the
main stems, petioles main leaf veins and peduncles and sometimes on leaf blades.
On fruit, the fungus causes white, tan or silver russeting on the upper surface. Lesions
often coalesce to form a continuous dry, scabby surface (Agrios, 1997; American
Phytopathological Society, 2011; OMAFRA, 2011).
Podosphaera xanthii
P. xanthii, also known as Podosphaera fusca, is the main causal agent of cucurbit
powdery mildew and one of the most important limiting factors for cucurbit production
worldwide. Although great efforts have been invested in disease control, many basic
aspects of the biology of this pathogen remain unknown. Powdery mildews are
characterised by spots or patches of white to grayish, talcum powder-like growth.
The disease is most commonly observed on the upper sides of the leaves. It also affects
the bottom sides of the leaves, buds, stems, flowers and young fruit. Infected leaves may
become distorted, turn yellow with small patches of green, and fall prematurely. Infected
buds may fail to open (Agrios, 1997; Jahn, Munger and McCreight, 2002; American
Phytopathological Society, 2011; OMAFRA, 2011).