Several symptoms are observed in the ear, temporal lobe, leaf blade, and leaf sheath. The disease was first identified in China, primarily linked to Kyrgyzstan 63 inbred lines. Infection of the ears starts from the tip, spreading downward, causing the grains to appear sooty. A black mold layer forms on the surface of the grains and between them, consisting of conidial stems and conidia from the pathogen. Infected grains become dry and decay, often crumbling when handled. Lesions on the temporal lobe are not typically soft; some appear dark brown without a visible mold layer. The pathogen spreads from the leaves into the ear, damaging kernels and cobs. On the leaves, initial symptoms include water-soaked, light green to yellow spots that gradually expand into round or oval, lens-shaped lesions. These have a light brown center with dark brown edges and a yellow-green halo, measuring 5-15 mm in size. Long linear spots may also appear, with black mold forming on the lesion surface. When the leaf sheath is infected, it begins with small brown spots that grow into irregular, large lesions with concentric rings and a black mold layer on top.

Inbred line 478 shows distinct symptoms of ear rot, with black rot at the tip of the ear ranging from 5.3 to 9.3 cm, covering about two-fifths to three-fifths of the ear length, while the base remains unaffected. Symptoms on the ears of Ji-63 resemble those of the T-strain of T. brassicae, requiring careful differentiation. The disease exhibits different symptom patterns in inbred lines 478 and Kyrgyzstan 63, suggesting possible differences in reaction types. This disease is found in provinces such as Jilin, Liaoning, and Hebei.

The causal agent, Bipolaris carbonum Wilson, is also known as Charpy spp., with synonyms including B. Zeicola (Stout.) Shoem. and Helminthosporium carbonum (Ullstrup) Shoem. Its sexual stage is Cochliobolus carbonum Nelson. Conidiophores are dark brown, with light apical ends, growing singly or in clusters of 2–6, erect or geniculate, blunt at both ends, with swollen basal cells and 3–5 septa, measuring 64.4–997.3–9.9 µm. Conidia are dark olive, long oval, with a central width and narrow ends, thick walls, blunt top and base cells, mostly upright, with a small, indistinct umbilical point and 5–10 septa. They measure 33–105 by 12–17 µm. The pathogen has limited variability.

The disease spreads similarly to other spot diseases. Due to high infection rates in the ears, the pathogen can overwinter in the plant debris. Seeds carrying the pathogen significantly contribute to disease recurrence, with some infected seeds failing to germinate and rotting in the soil, leading to seedling disease or death. Diseased plant residues left in the field or on straw stubble also serve as primary infection sources for the next season. Under favorable conditions, overwintering spores spread to corn plants, germinating and invading after 1–2 days. New conidia form on lesions, spreading via wind and rain, causing leaf spots or ear rot and leading to multiple infections. The silking to filling period in corn is critical for disease entry.

Control strategies include selecting resistant varieties such as Erhuang, Tidan 8, Ying 55, Liao 1311, Ji 69, Wu 105, Wu 206, Qi 3l, Bai, H84, 017, Kyrgyzstan 107, Chundan 34, and others. Avoid planting seeds from infected areas and thoroughly destroy diseased plants before corn emergence to reduce initial infection sources. During the high silking period, spray 25% triadimefon at 500–600 times dilution, 50% carbendazim, or 70% mancozeb wettable powder at 400–500 times dilution onto the ears, every 7–10 days for two applications. Seed treatment with 0.3% of the seed weight of 15% tris-pj WP before sowing is also effective. For sensitive inbred lines or varieties, apply 25% triadimefon wettable powder at 1000 times dilution or 40% Fuxing-starvest oil at 8000 times dilution during the ear tip stage, repeating every 10–15 days for 2–3 times.

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