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Plant: Watermelon (Citrullus lanatus) (Cucurbitaceae) Back to List Disease/Disorder: Gummy stem blight Causal agent:Didymella bryoniae (fungus) Phoma cucurbitacearum (anamorph, pictured) Signs: spore-producing bodies ("pycnidia") can be seen within leaf spots and stem tissue. Symptoms: leaves show darkened leaf spots usually with concentric rings.
Stems can have gummy exudate and cankers.
Total image number: 16
Plant: Cucumber and Muskmelon (Cucumis sativus and Cucumis melo subsp. melo) (Cucurbitaceae) Back to List Disease/Disorder: Anthracnose Causal agent:Colletotrichumorbiculare (fungus) Signs: spore-producing bodies ("acervuli") with dark sterile hairs ("setae") can be seen within blighted areas; no setae in the fruit lesions. Symptoms: spotting on leaves and tan lesions on the leaf petioles and stems,
sunken spots on the fruit Total image number: 20
Row 1: image on left is muskmelon, image on right is cucumber
Rows 2, 3, and 4: on cucumber
Rows 5 and 6: squash fruit
Plant: Cucumber, Muskmelon, and Pumpkin (Cucumis sativus, Cucumis melo subsp. melo, and Cucurbita sp.) (Cucurbitaceae) Back to List Disease/Disorder: Phytophthora fruit rot, Phytophthora root and crown rot Causal agent:Phytophthora capsici (fungus) Signs: white mycelium with spore-producing bodies ("sporangia") Symptoms: white mold on blighted portions of fruit and stems Total image number: 24
1st 3 rows are of cucumber - these images show the fruit rot phase
4th row is squash - these images show the crown/stem rot phase
5th and 6th rows of 'Queensland blue' pumpkin
Plant: Muskmelon and Cantaloupe (Cucumis melo subsp. melo) Back to List Disease/Disorder: Alternaria leaf blight Causal agent:Alternaria cucumerina (fungus) Signs: dark spores of this fungus are rather large and can be seen with a hand lens. Symptoms: tan to brown spotting on leaves Total image number: 11
1st row is of muskmelon
2nd and 3rd rows are of cantaloupe
Plant: Squash (Cucurbita spp.) (Cucurbitaceae) Back to List Disease/Disorder: Virus complex Causal agent: (virus) Signs: Symptoms: distorted leaves with mosaic blotches Total image number: 4
All we can say, without sending the sample off for a Cucurbit Virus Screen, is that it is one of the viruses and list the complex of cucurbit viruses: Cucumber mosaic (CMV), Watermelon mosaic (WMV), Zucchini yellow (ZYMV), Papaya ring spot virus type W (PRSV-W), and Squash mosaic (SqMV).
Plant: Pumpkin (Cucurbita spp.) (Cucurbitaceae) Back to List Disease/Disorder: Fruit rot Causal agent:Fusarium spp. (fungus) Signs: white/tan mycelium and spores masses Symptoms: white to tan spots on fruit with subsequent fruit decay Total image number: 14
1st row is a standard pumpkin.
2nd, 3rd, and 4th rows are from 'Lil ironsides' cultivar, Fusarium solani.
Plant: various Cucurbits (Cucurbitaceae) Back to List Disease/Disorder: Downy mildew Causal agent:Pseudoperonospora cubensis (fungus) Signs: downy mycelial growth in spots with lemon-shaped spores Symptoms: yellow blotchy areas with mold Total image number: 12
The first row is from a pumpkin plant (4 images).
The 2nd and 3rd rows are from a cucumber plant (8 images).
Plant: various Cucurbits (Cucurbitaceae) Back to List Disease/Disorder: Powdery mildew Causal agent:Podosphaera xanthii (fungus) Signs: White fungal growth over the upper and lower surface of the leaves Symptoms: ranging from very slight symptoms to browning to leaves Total image number: 13
These mages were of the fungus on pumpkin leaves.
The fungal structures in the last two images were not exposed to 3% KOH solution.
Plant: Pumpkin (Cucurbita spp.) (Cucurbitaceae) Back to List Disease/Disorder: Mycoparasite of Sphaerotheca fuligenea Causal agent:Ampelomyces quisqualis (mycoparasite on Powdery mildew) Signs: Pycnidia containing cylindrical to spindle-shaped, occasionally curved, conidia that are 7.5-9.0 X 2.5-3.5 micrometers.
In the image with three pycnidia of A. quisqualis in the third row, 6 hyline conidia of Sphaerotheca fuligenea can be seen. Symptoms: none without the aid of a microscope Total image number: 10
Plant: Cantaloupe (Cucumis melo subsp. melo) Back to List Disease/Disorder: herbicide injury Causal agent: "Roundup" 'glyphosate' Signs: Symptoms: Yellowing of youngest leaves from the base. Total image number: 4