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Plant: Corn (Zea mays) (Poaceae) Back to List Disease/Disorder: Gibberella stalk rot Causal agent:Gibberella (teleomorph) Fusarium (anamorph) (fungus) Signs: Perithecia of Gibberella are bluish black and superficial on stalk near nodes. Symptoms: stalk rot Total image number: 4
Plant: Corn (Zea mays) (Poaceae) Back to List Disease/Disorder: Diplodia leaf streak Causal agent:Stenocarpella macrospora (fungus) Signs: Pycnidia are seen immersed in the symptomatic leaf tissue. Symptoms: tan, necrotic leaf tissue in fairly large oval spots similar in size to that seen with Northern corn leaf blight. Total image number: 4
Plant: Corn (Zea mays) (Poaceae) Back to List Disease/Disorder: 1- Stinkbug injury.
2- Damping-off and seedling blight caused by the fungus Pythium. Causal agent: Stinkbug and Pythium sp. (fungus) Signs: Oospores of Pythium sp. Symptoms: With #1 there is symptomatic evidence of stinkbug feeding. With #2 incubation of hypocotyl and root tissue produced oospores (spore structures of the fungus) in the infected tissue (see four B&W micrographs). Total image number: 8
Plant: Corn (Zea mays) (Poaceae) Back to List Disease/Disorder: Corn smut Causal agent:Ustilago maydis (fungus) Signs: Smut galls (the fungus itself) can be formed on any part of the plant from near the soil line to tassels, but most commonly found in the ear. Symptoms: see below Total image number: 7
Plant: Corn (Zea mays) (Poaceae) Back to List Disease/Disorder: Crazy top Causal agent:Sclerophthora macrospora (fungus) Signs: none shown Symptoms: The left-most image is of a plant that had its tassel replaced by a mass of leafy tissue.
As for the image of the very tall plant, this plant had no ears but that would not account for the plant's height; it is likely just a genetic mutation. The last two images on the right show a wrapping of the terminal leaves, which can be caused by a growth regulator. Total image number: 4
Plant: Corn (Zea mays) (Poaceae) Back to List Disease/Disorder: Southern rust (suspected) Causal agent: Puccinia polysora Signs: The third image shows spores called "urediniospores".
The fourth images shows spores called "teliospores". Symptoms: The disease resembles common rust but with some subtle differences. Most of the rust pustules or spots of rust can be found on the upper leaf surface and there shape is rounded as opposed to common rust where they are more elliptical. The rust spores themselves are yellowish to reddish-gold whereas those of common rust are more chestnut brown. Total image number: 4
Plant: Corn (Zea mays) (Poaceae) Back to List Disease/Disorder: herbicide injury Causal agent: 'glyphosate' ("RoundUp") Signs: none Symptoms: newly emerging corn with yellowed new leaf tissue. Seedlings were just poking through the soil when herbicide was sprayed, several days after planting. Total image number: 4
