Why Are My Corn Seedlings Dying? 5 Common Reasons

There’s nothing more frustrating than planting corn and imagining juicy homegrown ears to roast on the grill, only to watch your seedlings get sick and die.

But seedlings are tender things, and I know how this feels. Back when I first started growing maize years ago, I planted some corn indoors with the intention of transplanting it outside with the arrival of warm weather.

Instead, the tiny shoots grew way too tall and then they slumped over, dead. I couldn’t understand why.

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In our guide to growing corn, we cover how to cultivate maize in your garden, but if you find your seedlings are looking sickly, you will need this guide.

I’ll reveal the top reasons why your seedlings might be dying and what you can do about it next time.

Here’s what I’ll cover:

Maize is susceptible to pests, diseases, cold weather, and other calamities throughout its life, but it is especially prone to problems when it is young.

Here are the top five reasons why your little seedlings might struggle to survive.

1. Not Enough Warmth

It might be tempting to rush out and plant corn seeds the moment you see the first dandelion pop up in your area. But your garden soil might not be ready to support seedling growth.

In order for corn seeds to germinate, the soil must warm up to 50°F, and not dip below that temperature throughout the day or night.

If a surprise frost hits the seedlings after they’ve germinated, this can spell trouble. A few hours of exposure to air temperatures between 28 and 32°F may not injure corn, but if temperatures drop below 28°F, the young plants will suffer.

At such low temperatures, the water inside the plant cells turns into ice crystals that rupture the cell walls as they take shape.

Once the temperature warms back up, the ice melts, causing the ruptured cells to lose water and nutrients. If enough cells are affected, the plant can die.

To prevent this from happening to your seedlings, especially if you live in Zones 3 to 5, your only option is to sow seeds indoors and wait to transplant them outside until two weeks after the danger of frost has passed.

This will probably be around late May or early June for gardeners in these colder regions.

The seedlings might not transplant well, but it’s worth a try to be able to harvest corn before the frost hits in the fall. Your best bet is to plant more seedlings than you think you’ll need, to account for potential loss after transplant.

2. Lack of Sunlight

If the newly emerged seedlings don’t receive at least six to eight hours of full sunlight a day, they will suffer.

If you’re growing them indoors, set them near a bright, sunny window and add a grow light to bookend the bright midday hours, since the filtered sunlight won’t be enough, and the corn will grow leggy and weak without enough light.

Make sure you position it just an inch away from the top of the seedlings, adjusting the light as the corn grows. Also, you’ll want to give the plant about 12 to 16 hours per day with a grow light.

I’m pretty sure lack of light was the issue that struck my seedlings back when I first tried to grow them indoors as a novice gardener.

I’ve started maize indoors since then, and it’s flourished because I adjusted a few light-related factors, including moving that grow light a lot closer. 

3. Fungal Diseases

Those of us in cooler, wetter growing zones get to deal with more fungal diseases than those in warmer, drier locales.

Planting corn in cold, wet soil makes it an easy target for fungal diseases, including damping off and seedling blight.

It’s important to note that these two terms are sometimes used interchangeably, although seedling blight more commonly refers to issues a seedling has once it has emerged, while damping off can affect seeds before they emerge. This is referred to more specifically as pre-emergent damping off.

If your seedlings turn yellow and wilt, or if they simply flop over and look damp and rotten at the base, they might be suffering from a fungal infection.

It can be nearly impossible to tell exactly which type of fungus is causing the infection, and sometimes, multiple types of fungi might be responsible!

The only way to know for sure what killed your plants is to send them to your local extension office for testing.

The most common fungal culprits that cause damping off species of Fusarium, which cause red-brown lesions on the young plants; Rhizoctonia, a tricky pathogen that shows no aboveground symptoms until plant death but that causes cankered, rotting roots; and Pythium, another “invisible” killer that causes dark lesions on the roots, which then rot and kill the plant.

These disease-causing pathogens easily overwinter in soil and on previously used gardening equipment. Damp conditions can increase the likelihood that they will emerge and destroy your young crop.

To prevent damping off:

• Always clean your gardening tools between uses.
• If you are reusing trays or containers, soak them for 30 minutes in a solution of 90% water and 10% bleach first, to kill off any lingering fungi.
• Use fresh potting mix and avoid using garden soil if you’re starting seeds indoors.
• Keep the seedlings in optimal conditions: give them enough warmth, enough sunlight, and just the right amount of water, and avoid adding fertilizer until they have at least four true leaves.
• Water seedlings with clean, room temperature water – 68-77°F is ideal.

You can learn more about corn seedling blight in our guide.

4. Herbicide Damage and Mineral Deficiencies

While it’s important to keep your garden clean and free of weeds, using herbicides can kill or damage young corn seedlings.

Even if you don’t use herbicides on your vegetable garden, if you use them on your lawn, the chemicals can drift over to your young plants and cause damage.

If young leaves look twisted, curled, knotted, or cupped, or they are lying flat on the ground, you might have a case of herbicide injury on your hands.

The most common lawn herbicides that also kill garden plants are those that contain 2,4-D, atrazine, dicamba, diquat, glyphosate, metsulfuron, and picloram.

So check the labels of your herbicides before you use them, or don’t use them at all. I personally embrace the abundance of cheery dandelions that pop up with my grass each year.

For seedlings that appear healthy except for certain abnormal colorations as described below, you might actually be dealing with a mineral deficiency.

A green leaf color that is unusually pale suggests a nitrogen or sulfur deficiency. Yellowed, dried-out leaf edges are probably caused by a lack of adequate potassium. If only the upper leaves are turning yellow, you’re likely looking at a magnesium deficiency.

For pale leaf color and yellowed leaf edges, apply a 10-10-10 NPK fertilizer. For a magnesium deficiency, add dolomitic lime (as opposed to calcitic lime, which does not have nearly as much magnesium in it) to the soil.

A phosphorus deficiency is easy to spot: the leaves turn purplish. This happened to my corn once, and I easily remedied it by adding phosphorus-rich bone meal to the soil around the plants every two weeks or so.

The best way to prevent mineral deficiencies is to conduct a soil test before you start growing corn. A little work before you plant can save you from a big headache later on!

But if you don’t do a soil test and you end up having issues with mineral deficiencies, it’s easy to find fertilizers and plant supplements to help replenish a lack of nutrients once you know what you’re dealing with.

5. Pests

Out of the many pests that can plague Z. mays, there are two that threaten young seedlings in particular: cutworms, particularly the black cutworm (Agrotis ipsilon), and corn wireworms (Melanotus communis).

Black cutworms are the larvae of a species of moth that lay their eggs on weeds and maize leaves. The brownish-black larvae are 1/8 of an inch long when they emerge, but they grow to a whopping two inches just before they leave the larval stage.

Cutworms do what their name suggests: they eat through the seedlings either just below the ground or just aboveground, resulting in visible decapitation or sudden wilting.

Present throughout most of the United States, while they can’t survive freezing temperatures, they migrate south in the fall and come back up north in the spring.

Wireworms, which are the larvae of click beetles, do the same by gnawing the roots and eating up through the young corn stems. Wireworms are orange-red in color and are about a half to one and a half inches long.

These pests are widespread in the midwestern and southeastern United States in particular, though they can be found nearly everywhere in the US, and around the world.

If you notice evidence of a cutworm infestation, remove and destroy as many of the worms as you can find.

NemAttack Pro Sc

Release beneficial nematodes into the planting area, like these Steinernema carpocapsae (Sc) beneficial nematodes from Arbico Organics.

If I catch sight of wireworm damage, l carefully disturb the soil near my corn plants by tilling it with a hand trowel to see if I can find any worms to manually remove.

Or, you could apply an insecticide that contains sulfur and pyrethrins, which work as a knockdown insecticide against click beetles.

Bonide Tomato and Vegetable Spray

I like this tomato and vegetable spray from Bonide, available at Arbico Organics.

Find more information on combating cutworms here.

Promote the Growth of Healthy Young Shoots

Now that you know the five most common reasons for sickly corn seedlings, you can plant your maize in ideal conditions and keep a close eye on it to catch potential problems early.

This’ll give you a chance to enjoy those juicy kernels or puffs of popcorn later on.

Have you ever dealt with sick seedlings before? Let us know in the comments section below!

And in the meantime, for more information on growing corn in your garden, check out these guides next:

• 9 of the Best Companion Plants to Grow with Corn
• How to Hand Pollinate Corn
• When and How to Harvest Corn
• 11 of the Best Varieties of Sweet Corn to Grow at Home

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