Head smut
Sphacelotheca reiliana
What is Head smut (Sporisorium reilianum)?
Sporisorium reilianum (formerly Sphacelotheca reiliana) is a biotrophic fungus that infects maize(corn) and sorghum, causing head smut. It replaces the reproductive structures such as tassels, ears, and panicles with conspicuous galls covered by a fragile membrane. The membrane breaks easily, exposing dark brown spores and vascular bundles. Head smut is distinguished from common smut by its membrane consistency and the presence of vascular bundles. There are two specialized forms of S. reilianum: f. sp. reilianum for sorghum and f. sp. zeae for corn.
How does Head smut (Sporisorium reilianum)?
Sporisorium reilianum reproduces through sexual and asexual means. Teliospores are formed in infected tissues, germinating into basidiospores that disperse to infect new plants. The fungus forms spore masses called sori within the host, containing numerous spores. Upon maturation, sori rupture, releasing spores for further spread. Asexual reproduction also occurs within infected tissues. This reproductive cycle enables Sporisorium reilianum to persist and infect maize and sorghum, causing head smut.
Symptoms
1 - Crop Effects
• Head smut causes significant yield losses in maize and sorghum by replacing reproductive structures with spore masses. • Infected ears and panicles may have reduced grain quality due to spore presence.
2 - Soil Effects
• Sporisorium reilianum's dormant teliospores in soil or debris contribute to disease persistence. • Abundant spores are dispersed by wind, water, or human activities, spreading the disease to nearby fields.
3 - Environmental Effects
Head smut disrupt agricultural ecosystems, affecting crop productivity and food resources for wildlife.
Solutions
1 - Preventions
• Planting resistant maize, sorghum and other crop varieties can provide effective protection against head smut. • Implement long rotations to reduce the presence of teliospores in the soil, as they can remain viable for extended periods. It will help in breaking the disease cycle. • Removing and destroying infected plant debris, including tassels and ears, can help reduce the inoculum source. • Using disease-free seeds from reputable sources helps prevent the introduction of Sporisorium reilianum. • Ensure balanced soil fertility to promote plant vigor and enhance their natural resistance to diseases.
2 - Treatment
• Treating seeds with fungicides or hot water treatment can reduce the initial inoculum and prevent seed-borne infection. • Common fungicides used for head smut management include azoxystrobin, propiconazole, thiophanate-methyl, trifloxystrobin, tebuconazole, and flutriafol. • Availability and specific brand names may vary depending on location and regulations. Consult local agricultural authorities or pesticide specialists for approved fungicides and proper usage guidelines.
