Plant Pathology
Factsheet

Corn seeds and seedlings are susceptible to infection by a number of soilborne fungi. When planted into cool, wet soils, seeds may decay before or after germination. After emergence, seedlings may show the following aboveground symptoms: stunting, yellowing and/or reddening of older leaves, marginal burning of leaves, and "tall plant/short plant" syndrome. Recognize, however, that these symptoms may also be due to non-infectious problems, like poor phosphorous uptake in cool soils. If infectious diseases are involved, roots--especially tips--exhibit a variety of symptoms of rot: collapsed or firm, grayish-white to purple to brown decay.

Fungi that are commonly associated with seed and seedling diseases of corn include common soilborne fungal pathogens: Fusarium, Pythium, and Rhizoctonia. Diplodia, an ear rot fungus, can also cause seedling disease, but is not commonly observed.

Affected plants may go on to produce an ear if nodal roots develop normally. Severely affected plants may die from an inadequate root system during stressful weather.

Seed and seedling diseases of corn can be minimized by planting seed treated with captan or thiram fungicides into soils warm enough to promote prompt germination and emergence. A good guideline is to postpone planting until the soil temperature is at least 50-55 F at a two-inch depth when measured around sunrise.

Often, seedling diseases in corn are an indication of some other problem which predisposed plants to infection. Possible predisposing stresses include: fertilizer burn; misplacement of soil pesticides; herbicide injury; soil compaction; a seed furrow with slick, compacted side walls, and so on. Some detective work out in the field and with field records is often necessary to identify the factor ultimately responsible.