Corn Stunt

Growing corn makes a dramatic statement in the garden. Reaching ten feet or more, modern corn plants can be grown alongside other garden giants, such as sunflowers and hollyhocks. Unless they become infected with corn stunt, that is.

Corn growing in schoolyard (Michael Zimmer) CC BY-SA 2.0

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 practically eliminating kernel production.

Corn stunt disease complex

Some people see corn stunt as a single disease. Other people see it as part of a complex along with maize bushy stunt mycoplasma and maize rayado fino virus (MRFV). Other people include maize chlorotic dwarf virus in the corn stunt complex. Any combination of these diseases can be devastating to your corn crop. [And you don't need to remember all the names to be able to see there is a problem.]

Corn stunt symptoms

Healthy corn plants produce one or two ears of corn, depending on whether they are early or late-maturing varieties. Plants infected with corn stunt are significantly shorter, 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 in completely. You end up with a lot of empty spaces. The kernels that 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.

Corn plant infected with corn stunt (Clemson University Extension, CC BY-SA 3.0)

How corn stunt spreads

Corn stunt is carried by leafhoppers. Corn leafhoppers (Dalbulus maidis), in particular, host the bacteria (Spiroplasma kunkelii), 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. The first generations of emerging bacteria are less effective at spreading the disease than those that occur later in the season. Insecticides are generally not effective.