IPM Identification and Mangement Of Turfgrass Diseases

Author(s)

Rust

Pathogen: Puccinia spp.
Hosts: All turfgrasses

Symptoms and signs

From a distance, rust-infected turf appears dull yellow or dark brown to purple (Figure 1). The rust fungi that infect turfgrasses produce two types of spores that are easily observable in grass leaf blades. The first to develop are urediniospores. The fruiting bodies containing urediniospores rupture the leaf epidermis, resulting in rust pustules that are visible to the naked eye (Figure 2). Rust pustules range in color from cinnamon brown to orange or yellow, depending on the species of rust fungus (Figure 3). The powdery spore mass rubs off easily on fingers, shoes or clothing. The color, size and shape of urediniospores vary with Puccinia sp. (Figure 4). Urediniospores serve as a source of inoculum to reinfect healthy turfgrass in the local area or, when wind-borne, to initiate infection in other areas.

The disease may be more difficult to diagnose later when pustules turn black (Figure 5). The blackened fruiting bodies contain a second type of spore — teliospores (Figure 6). Teliospores germinate to produce basidiospores that are dispersed by wind to infect alternate non-grass hosts. Although sexual reproduction and recombination occurs on the alternate host, which varies with rust species, this stage of the rust disease cycle is considered of minor importance in turfgrass. Continuous heavy infection causes grass blades to turn yellow, wither and die, resulting in stand thinning (Figure 7). Severely rusted stands are more prone to winterkill.

Conditions

The rust fungi (Puccinia spp.) overwinter as urediniospores in infected plants or are reintroduced each summer by wind-blown spores. Infection of leaf blades is favored by moderate temperatures (68 to 85°F) and extended wet periods. The disease tends to be more severe in partially shaded areas, such as under trees or along fence rows. Once infection occurs, slightly higher temperatures favor symptom development. Turfgrasses under stress (nutrient deficiency, drought, shading, close mowing heights and high temperatures) are more likely to be seriously damaged by the disease.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.