Why Are My Corn Ears Going Mouldy on the Plant?

Peeling back the husk to find white, pink, grey or black mould growing on the kernels is concerning — both because it ruins the harvest and because some ear moulds produce mycotoxins that make corn unsafe to eat. Mould on corn ears is broadly called "ear rot" and there are several fungal species that can cause it, each looking slightly different and entering the cob through different routes.

How mould enters the ear

Fungal ear rots almost always enter through a wound or weakened point. The most common entry routes are: damaged silks (from insects or mechanical damage) that leave the tip of the cob exposed; earworm damage at the tip, which creates an open wound; husk leaves that have split or not closed tightly, allowing moisture to penetrate; and unharvested cobs left too long on the plant after maturity, where the tip begins to dry, crack and become susceptible. Keeping the husk intact and harvesting promptly at maturity removes most of the risk.

Fusarium ear rot (pink or white mould)

Fusarium species cause a pinkish-white mould, often appearing at the tip of the cob where earworms have fed or where the husk has been damaged. Fusarium ear rot is one of the more common types in home gardens. Infected kernels may be pink or have a "starburst" pattern. Cut away and discard any mouldy kernels and use the remainder promptly. Fusarium can produce fumonisins (mycotoxins) in heavily infected cobs — if more than a small portion of the cob is affected, discard the whole ear.

Gibberella ear rot (red-pink mould from the tip)

Gibberella infection produces a distinctive red-pink mould that spreads from the tip toward the base. It is more common in cool, wet conditions during silking. Gibberella can produce deoxynivalenol (DON, also called vomitoxin) and zearalenone — both harmful mycotoxins. Any cob with visible Gibberella ear rot should be discarded entirely and not fed to animals either.

Preventing ear rot

Control earworm promptly so it does not create entry wounds at the tip. Harvest as soon as cobs are at peak maturity — do not leave ripe cobs on the plant for more than a week. Avoid overhead irrigation once silks have browned. Ensure good airflow between plants. After harvest, remove and dispose of all corn debris, which can harbour spores for the following season.