What is the Difference Between Rust and Smut

The key difference between rust and smut is that rust is a fungal disease that causes a rusty yellow appearance in affected plants, while smut is a fungal disease that causes a sooty, black appearance in affected plants.

Rust and smut are fungal diseases that affect plants. Rust and smut are perhaps the most economically important plant fungal pathogens. Rusts are identified to be more dangerous fungal pathogens to agriculture, forestry, and horticulture, while smuts mostly affect cereal crops, which are the members of the grass family (Poaceae) and sedges (Cyperaceae). Moreover, it is highly important to know about these fungal diseases as they affect a large variety of plants, including valuable crop plants.

CONTENTS

1. Overview and Key Difference
2. What is Rust 
3. What is Smut
4. Similarities – Rust and Smut
5. Rust vs Smut in Tabular Form
6. Summary

What is Rust?

Rust is a fungal disease that causes a rusty yellow appearance in affected plants. Rust plant disease is caused by pathogenic fungi of the class pucciniomycetes. An estimated 168 rust genera and approximately 7000 species have already been identified. Rust fungi are highly specialized plant pathogens. They have several unique features. Rust fungi are diverse and affect different kinds of plants. Anyhow, each rust species has a very narrow range of hosts. They cannot be transmitted to non-host plants. Moreover, most rust fungi cannot grow in pure cultures as well. A single species of rust can infect two different plant hosts in different stages of its life cycle. It may produce up to five distinct spore-producing structures such as spermogonia, aecia, uredinia, telia, and basidia in the stages of reproduction. These spores are host specific. Each spore can typically infect only one kind of plant.

Furthermore, rust fungi are obligate plant pathogens. The infection begins when a spore lands on the plant surface. This spore germinates and invades its host. The signs of infection include stunted appearance, chlorotic (yellowed), rust fruiting bodies, etc. However, rust can be managed using fungicides such as mancozeb or triforine.

What is Smut?

Smut is a fungal disease that causes a sooty, black appearance in the affected plants. Smuts are multicellular fungi. They are characterized by large numbers of teliospores. These fungi mostly belong to class ustilaginomycetes that cause plant diseases. Smut fungi usually affect cereal crops. They most notably affect members of the grass family and sedges.

Smut disease can be observed in economically important crop plants such as barley, maize, wheat, oats, sugarcane, and forage grasses. After infection, smut fungi hijack the reproductive systems of plants, forming galls that darken and burst. This process releases fungal teliospores that infect other nearby plants. Fungicides propiconazole, flutriafol, imazalil sulphate, carbendazim, tebuconazole and azoxystrobin are typically used to manage the smut disease.

What are the Similarities Between Rust and Smut?

• Rust and smut are fungal diseases affecting plants.
• These fungi are obligate plant pathogens.
• The mycelium in both fungi that cause rust and smut diseases pass through two stages; the monokaryotic (primary) stage and dikaryotic (secondary) stage.
• Both rust and smut are observed in most economically important plants.

What is the Difference Between Rust and Smut?

Rust is a fungal disease that causes a rusty yellow appearance in the affected plants, while smut is a fungal disease that causes a sooty, black appearance in the affected plants. So, this is the key difference between rust and smut. Furthermore, rust is caused by heteroecious and autoecious fungi, while smut is only caused by autoecious fungi.

The following infographic lists more differences between rust and smut in tabular form for side by side comparison.

Summary – Rust vs Smut

Rust and smut are fungal diseases seen in plants. They are obligate plant pathogens. Rust is a fungal disease that causes a rusty yellow appearance in the affected plants, while smut is a fungal disease that causes a sooty, black appearance in the affected plants. Thus, this summarizes the difference between rust and smut.

Reference:

1.“Learn About Plant Rust Disease And Rust Treatment.” StackPath.
2. “How a Smut Fungus Prepares to Infect.” ELife, ELife Sciences Publications, Ltd, 2 Dec. 2019.

Image Courtesy:

1. “Rust fungus – Flickr – gailhampshire” By gailhampshire from Cradley, Malvern, U.K – Rust fungus (CC BY 2.0) via Commons Wikimedia
2. “Smut fungus” By UGA CAES/Extension (CC BY-NC 2.0) via Flickr