Maize Head Smut Disease Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

The Maize Head Smut Disease is a devastating fungal disease of maize caused by Sphacelotheca reiliana and is believed to have originated in Mexico. This disease can cause significant losses in maize yield as the galls replace kernels that would normally develop on the ears of the corn.

The disease can also cause the stunting of plants and often occurs along with other fungal diseases such as rust, leaf blight, and stalk rot. To effectively manage this disease, it is important to understand its disease cycle, the mode of disease spread, and the best methods for controlling it. This article will provide an overview and discussion of the Maize Head Smut Disease in Maize crops, including its symptoms, identification techniques, and control.

Maize Head Smut Disease Management

The Causal Organism of Maize Head Smut Disease

Sphacelotheca reiliana is a soil-borne obligate parasite that belongs to the Family Microbotryaceae of Order Microbotryales of the Phylum Basidiomycota.
The characteristic features of this pathogen include the production of a dark brown to black spore mass known as a teliospore.
The smut galls are round swollen tissue masses containing these spores on the plant’s surface. The smut galls are also known as sori.

The Disease Cycle of Maize Head Smut Disease

The disease cycle of the Sphacelotheca reiliana pathogen begins with releasing the primary source of inoculum, chlamydospores, from the black or dark brown galls on the maize heads. These spores are transmitted by wind and rain and can persist in the environment for at least two or three years. If the conditions are right, the spores will land on a maize plant and begin to germinate.

Once the spores have germinated, the fungal hyphae will enter the maize plant through its stomata or small openings in its leaves. Once inside the plant, the fungus will spread throughout the plant’s tissues and begin to produce more spores. These spores will be released from the plant, spreading the disease to nearby plants. The infection can spread rapidly and cause significant damage to the maize crop.

As the disease progresses, the affected heads will turn black or dark brown and form galls. These galls will contain large quantities of spores, which can spread to other plants, infect them, and start the cycle again.

Occurrence of Maize Head Smut Disease in Maize Crop

Location of Maize Head Smut disease: This disease occurs in maize crops in the USA, Mexico, Colombia, Argentina, Brazil, Ecuador, Peru, Africa, India, China, Japan, Korea, Thailand, Hungary, Italy, and Spain.
Host range: The most common crops affected by Maize Head Smut Disease are maize, barley, oats, wheat, sorghum, millet, rye, and triticale.

Favorable Conditions for Maize Head Smut Disease Spread in the Field

Low soil fertility and poor soil drainage also favor infection, as these conditions can lead to an accumulation of moisture in the soil.
Overcrowding of plants, high humidity levels, and heavy rainfalls can increase the chance of disease transmission from plant to plant.
Moist soil, warm temperatures, and humid environmental conditions favor the growth of the fungus and the spread of the disease, with infection occurring most frequently during the summer months when temperatures are highest.

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Damage Symptoms of Maize Head Smut Disease

The primary symptom is the presence of blackened, smutted structures on the cob and tassel of the maize plant, which are referred to as ‘smut galls.’ These are the sites at which the fungus produces its spores. Infected plants remain stunted, with poor vigor and poor yield, showing a yellow or white discoloration of the leaves and ear and dieback of leaves. This disease affects the maize plant’s reproductive organs by destroying the inflorescence and producing black, sooty-looking spores, which are then dispersed by wind.

The fungus infects maize plants at the flowering stage and causes smut galls to form on the ears of the corn. These galls are dark-brown, hard, and spore-filled and can cause serious yield losses. The spread of the disease is favored by warm and humid conditions and is typically spread by wind or rain and through contaminated seed or crop debris.

Percentage of Yield Loss due to Maize Head Smut Disease in Maize Crop

The disease has caused 10-15% yield losses in the United States. In Mexico, yield losses range from 20-30%. In India, yield loss is around 40%. In China, a 20-30% yield loss is seen.
In Africa, yield losses are between 10-90%. In Peru, it is around 10%. In Brazil, it was 15-25%. The Economic Threshold Level is generally determined at 5-10% of the total maize heads infected with the disease.

Cultural Control measures of Maize Head Smut Disease

Avoid overcrowding: The plants should be spaced out in the field to ensure adequate airflow between them so that the disease does not infect the healthy plants on contact.
Crop rotation: Rotating maize with other non-host crops, such as pulses, can help reduce the risk of disease incidence.
Roguing out: Removing and burning the infected plants is necessary to prevent the spread of this disease throughout the field by contact with the infected plants.
Sanitation: It involves removing crop residues from the field and cleaning equipment after harvest to reduce the number of spores and fungi available to cause infection.

Biological Control measures of Maize Head Smut Disease

The naturally occurring Biocontrol agents such as the fungus Trichoderma harzianum, the bacterium Bacillus subtilis, and the nematode Steinernema feltiae are effective methods of controlling the maize head rust disease caused by the pathogen Sphacelotheca reiliana. These organisms can be applied to the maize crop as a powder or liquid, which is then taken up by the plant and spread throughout the crop. The biocontrol agents are effective at controlling the disease in maize and can also help to reduce other fungal diseases in the crop.

Chemical Control measures of Maize Head Smut Disease

The common fungicides used to control head smut disease in maize are Chlorothalonil, Mancozeb, Propiconazole, Azoxystrobin, and Copper fungicides.
Seed treatment – Treat the seeds with Thiram or Captan of 4 grams per kg of seeds.

Preventive Measures for Control of Maize Head Smut Disease

Removing infected plants, reducing crop density, and avoiding late planting, can reduce the spread of the disease.
Planting maize crops earlier in the season can reduce the spread of the disease, as the maize plants will be more mature and less susceptible to the disease when the pathogen is most active.
Regularly monitoring fields for signs of disease will help to catch and manage it early before it spreads.
Practice sanitation, tillage, and crop rotation methods to suppress disease development. Ploughing down the crop debris will reduce early infection in the crop.

In case you missed it: Maize Rust Disease Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

Conclusion

The maize head smut disease is a major threat to maize crops worldwide. It can cause significant yield losses, reduce grain quality, and increase the risk of contamination with mycotoxins. Thus, farmers must take proactive steps to prevent, manage, and control this disease. Adopting an integrated pest management approach that involves cultural, chemical, and biological control measures can help reduce the spread and impact of this disease.

Maize Head Smut Disease Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

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