Description of the Disease
Rust begins as small yellow spots on leaves and stems that form elongated, reddish-brown or orange pustules. Shoes and clothes are often stained orange by the spores when walking through infested areas. Rust kills leaves and debilitates plants when it is severe. The turfgrass quality is reduced because of poor color and reduced plant vigor. Rust survives as dormant mycelia in infected plants and as teliospores; it may spread to turf from infections on other grasses and woody ornamentals.
Susceptible Turfgrasses
Bluegrasses, ryegrasses, zoysiagrass, and tall fescue.
Conditions Favoring Disease
Moderately warm, moist weather favors rust development. Moisture in the form of dew for 10 to 12 hours is sufficient for the spores to infect plants. Warm air temperatures (70°to 75°F) and extended periods of leaf wetness favor the development of the disease. The disease is more severe in turf deficient in nitrogen.
Management
Rust can usually be managed with proper mowing, fertilizing, and irrigation practices.
Cultural Control
To reduce the incidence of rust, maintain turfgrass vigor by applying adequate but not excessive nitrogen fertilization and irrigate in the morning according to the evapotranspiration needs of the turfgrass. Provide good air movement on the surface of grass. Mow the turfgrass regularly and remove clippings if the lawn is infected to reduce the number of spores. Mixtures of several compatible turfgrass species fare better against rust than turfgrass composed of a single species. Most Kentucky bluegrass and tall fescue varieties currently marketed in California are fairly resistant to rust.
Treatment Decisions
Rust can usually be managed successfully through cultural practices, but in severe cases fungicide applications can be made.
| Common name | Amount to use | Ag Use REI‡ |
NonAg Use REI‡ |
|
|---|---|---|---|---|
| (Example trade name) | (hours) | (hours) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | AZOXYSTROBIN | |||
| (Heritage) | 0.2–0.4 oz/1000 sq ft | 4 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) | ||||
| B. | CHLOROTHALONIL | |||
| (Daconil Action) | Label rates | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) | ||||
| C. | MANCOZEB | |||
| (Fore 80WP, Dithane M-45) | 4 oz/1000 sq ft | 24 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M3) | ||||
| COMMENTS: Dithane M-45 registered for use on sod farms only. | ||||
| D. | MYCLOBUTANIL | |||
| (Eagle 20EW) | 1.2 fl oz/1000 sq ft | 24 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) | ||||
| E. | PROPICONAZOLE | |||
| (Banner Maxx) | 1–2 fl oz/1000 sq ft | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) | ||||
| F. | THIOPHANATE-METHYL | |||
| (Fungo Flo) | Label rates | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1) | ||||
| G. | TRIADIMEFON | |||
| (Bayleton 50 Turf and Ornamental) | Label rates | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) | ||||
| H. | TRIFLOXYSTROBIN | |||
| (Compass) | Label rates | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) | ||||
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode-of-action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode-of-action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to a fungicide with a different mode-of-action group number. |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production. |