Growing your own corn makes a dramatic statement in the garden. Reaching 10 to 12 feet in height, modern corn plants grow in tandem with other giants, such as sunflowers and hollyhocks. Unless they become infected with corn stunt.
Corn stunt does not mean ears of corn will suddenly start doing gymnastics over the fence into your neighbor’s yard. Instead, this bacterial disease will infect the phloem of corn plants, reducing them in size and all but eliminating kernel production.
Corn stunt disease complex
Some people see corn stunt as a single disease, while others see it as one part of a complex of three disease, the other two being maize bushy stunt mycoplasma and maize rayado fino virus (MRFV). Yet others include maize chlorotic dwarf virus in the corn stunt complex. Any combination of these diseases can be devastating to your corn crop.
Corn stunt symptoms
Healthy corn plants produce one or two ears of corn, depending on whether they are early or late maturing varieties, respectively. Plants infected with corn stunt are significantly shorter than normal, often only 5 feet tall, and may produce 6 or 7 ears. That may sound great, but it’s not. These ears are small and they do not fill properly, meaning there ends up being a lot of empty spaces. The kernels that do develop are not well attached, in a condition known as “loose tooth ears”. Infected plants will also exhibit pale yellow new leaves at the top. As these leaves mature, they tend to turn reddish.
How corn stunt spreads
Corn stunt is caused by Spiroplasma kunkeliiI, which is carried by leafhoppers. Corn leafhoppers (Dalbulus maidis), in particular, carry this disease with them, spreading it as they feed.
Corn stunt management
You can prevent corn stunt by using reflective mulches that deter leafhoppers. Planting your corn as early as possible in the growing season has been shown to reduce the impact of corn stunt infections. Apparently, the first generation of emerging bacterium are not as effective at spreading the disease as those that occur later in the season. Insecticides are generally not effective.
Juicy, sweet kernels of corn transform, overnight, into hideous, purple-grey, tumors. And these tumorous galls are delicious!
Introducing, corn smut.
Now, corn has many pests and diseases: corn earworms, European corn borers, seed-corn maggots, soft rot, seed rot, fusarium root and ear rot, maize dwarf mosaic, pythium stalk rot, and damping-off disease, just to name a few. If you are an American corn farmer, corn smut is not what you want to see in your field. A lot of money and effort have gone into eradicating corn smut in North America.
Corn smut in your garden is something else entirely.
While this distant cousin of mushrooms reduces crop size and makes ears of corn unmarketable for July picnics and canning purposes, it is edible and delicious. Unlike other corn problems, corn smut is said to taste like truffles, with a sweet, earthy, inky flavor. If it appears in your garden and you don’t want it, your local chef would love to hear from you!
To my way of thinking, if life gives you lemons, make lemonade. Or, if you are given corn smut, make quesadillas! Corn smut can be eaten raw, or added to many dishes, such as omelets, soups, sauces, meat dishes, or even desserts! As an extra bonus, corn smut is high in lysine. This means eating it with corn, or any other seed, provides a complete dietary protein.
Corn smut description
Also known as devil’s corn, common smut, boil smut, Mexican truffles, or huitlacoche [pronounced weet-la-COH-cheh], corn smut is a parasitic fungus that can occur on any aboveground portion of a corn plant as purplish blobs covered with papery greenish-white tissue. These fungi prefer meristem tissue and the galls are mostly seen on the ears of corn. Ear galls are significantly larger than those which form elsewhere on the corn plant.
Corn smut gets its purple color from pigments called anthocyanins. These are the same pigments found in blueberries, raspberries, and purple cauliflower. When you cook with corn smut, don’t be surprised to see the purple color change to black, because it will. Purple pigments generally don’t hold up well to heat.
Corn smut lifecycle
The corn smut fungus (Ustilago maydis) infects plant ovaries, causing kernels to swell up into large purple galls that are filled with fungal threads, called hyphae, and spores. Corn smut spores are already in the soil and can be carried on the slightest breeze or splashed water from rain or irrigation. Dry conditions and temperatures between 78°F and 93°F are all that corn smut needs to get started. Adding nitrogen or applying manure increases the chance of corn smut developing on your corn plants. Plant injuries also increase infection rates.
Corn plants try to defend themselves against corn smut by blasting the invaders with reactive oxygen (hydrogen peroxide). Sadly, from the corn plant’s perspective, this bubbling action simply spreads the smut spores.
If smut appears on your corn, fear not! Instead, harvest the galls while they are young and have the texture of a foamy popcorn, kind of firm and spongy. These moist galls are ready for harvesting 2 or 3 weeks after infection appears. As the galls mature, they turn dry and are mostly filled with unappetizing dry, black fungal spores.
Love it or hate it, corn smut is here to stay, so you may as well learn to cook with it (or sell it).
Corn is the biggest U.S. grain crop and you can grow it, too!
Fresh from the garden ears of sweet corn, heated, and then topped with butter, salt, and pepper, well, life just doesn’t get much better than that! Now, we are not talking about the corn used to feed livestock. That brand is called grain corn. Sadly, I wasn’t particularly happy with my Indian corn crop experience, either. It may have historical merit, but the kernels were tough and very starchy. Call me spoiled, but I prefer my corn with fat, sugar-filled kernels that burst on my tongue with every bite.
History of corn
For anyone who has had the opportunity to explore Mitchell, South Dakota, you know there’s a lot to be said for corn. Corn, or maize, was domesticated by people in what is now Mexico nearly 10,000 years ago. Early corn plants only grew 1-inch long cobs, and only one cob per plant. Selective breeding brought us to cobs of several inches in length and plants capable of producing multiple cobs on each plant. One of the three most genetically modified crops, nearly 90% of the U.S. corn harvest is of GMO corn. In addition to being eaten from the ear, or as grits or meal, corn (Zea mays) is also used as a sweetener (high fructose corn syrup), biofuel, and to make plastics, fabrics, adhesives, and liquor. There are six types of naturally occurring corn (and 142 GMO types, as of 2015). Those six types are dent corn, pod corn, flour corn, flint corn, popcorn, and our beloved sweet corn.
How corn grows
Being a member of the grass family (Poaceae or Gramineae), corn is cousin to bamboo, rice, and your lawn. Corn grows a hollow stem that is wrapped with leaf blades. Each corn plant produces both female and male flowers, but they are not self-pollinating. This is called monoecious. These flowers both start out bisexual (referred to as ‘perfect’ in the world of botany), and then develop into one gender or the other.
Corn kernels are actually female inflorescences, or flower clusters, that turn into fruit. These fruits are protected by tightly wrapped leaves that we call husks. At the top of each stem (or cob) is a male inflorescence (tassel) that releases pollen onto the wind. The silks we work so hard to remove are actually elongated stigmas from the female flower. There is an ovary at the end of each silk thread that must be pollinated for fertilization to occur, allowing a kernel to develop. Since pollen is carried on the wind, corn must be planted in blocks, rather than rows.
How to grow corn
Corn needs lots of nutrients in the soil, so be sure to prepare the beds ahead of time with plenty of aged compost. Corn does not transplant very well, so wait a couple of weeks after your last frost date before planting. Seeds should be planted one inch deep and 4 to 6 inches apart. Soil needs to be at least 60°F for germination to occur. Once your corn seedlings emerge, thin them to 8 to 12 inches apart. Corn plants have very shallow roots, so proper irrigation is important. In the heat of summer, your corn plants may need an average of 5 gallons of water per square yard each week. Since each microclimate is different, you will have to make your own adjustments. Just keep in mind that insufficient irrigation can reduce the number of silks that emerge and that means less developed kernels on your ears of corn. One way to give your corn seedlings an extra boost of nitrogen is to use the Three Sisters Method and plant corn with beans and squash. The beans ‘fix’ atmospheric nitrogen, making it available to nearby plants, and the squash produce large leaves that shade the soil.
Corn pests and diseases
We are not alone in our love of corn. An old saying tells us, “One for the blackbird, one for the crow, one for the soil, and one to grow.” You may or may not be able to scare away the crows (and chickens) with scarecrows (I use my dogs), but nothing can stop a determined raccoon. It is the smaller pests, however, that will probably cause you the most problems. These generalists include: armyworms, aphids, spider mites, thrips, wireworms, cutworms, flea beetles, cucumber beetles, and grasshoppers. Corn-specific pests you might see are leafhoppers, leaf miners, seed-corn maggots, and corn earworms. Corn is also subject to fungal and bacterial diseases, such as smut, soft rot, fusarium root and ear rot, maize dwarf mosaic, pythium stalk rot, seed rot, and damping-off disease. Of course, corn smut really is delicious, so don't panic if it shows up.
Sweet corn loses its sweetness soon after harvesting, so pick it as you will be eating it. Corn is ready for harvest when the tassels turn brown. If your harvest is bigger than you can eat, corn freezes well.
If you have a patch of ground, give corn a try!
You can grow a surprising amount of food in your own yard. Ask me how!
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