Symptoms and Signs
Rust begins as small, grayish purple pustules on the underside of older leaves. As pustules mature, the leaf tissue ruptures to expose red-brown uredospores. Premature leaf senescence and death occur. If favorable conditions continue, the rust infections progress up the stem of the plant to younger leaves.
Comments on the Disease
Rust in bermudagrass seed fields is often not obvious in the early stages. The first indication of a problem may be red-brown rust spores clinging to the shoes and lower pant legs of scouts walking through the seed field. The causal fungus, Puccinia cynodontis, survives on infected bermudagrass and bermudagrass residues in the field as well as in weedy borders and ditches. Humid, moderate temperatures are conducive to rust disease development. Periods of leaf wetness (dew) must occur for infection to take place.
Management
Cultural Control
Keep plants growing vigorously with adequate, but not excessive, nitrogen fertilization and irrigation. If possible, irrigate during normal dew periods so plant foliage is not wet any longer than normal night and morning leaf wetness periods. Remove straw from the field by burning (preferred) or baling.
Chemical Control
Apply fungicides as soon as environmental conditions favor rust development or when rust pustules first appear.
| Common name | Amount per acre** | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| 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, efficacy, application timing, honey bees, and environmental impact. Always read label of product being used. | ||||
| A. | TEBUCONAZOLE | |||
| (Folicur) 3.6F | 4–8 fl oz | 12 | 4 | |
| MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) | ||||
| COMMENTS: Read label for restrictions if bermudagrass seed is used for animal feed. | ||||
| B. | PYRACLOSTROBIN | |||
| (Headline) | 6-12 fl oz | 12 | 14 | |
| MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) | ||||
| COMMENTS: Do not graze or feed for age or hay to livestock within 27 days of last application. | ||||
| C. | SULFUR | |||
| (various) | 3–10 lb (80% sulfur) | 24 | 0 | |
| MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M2) | ||||
| COMMENTS: Was not effective in 2 replicated trials conducted in Imperial County. | ||||
| ** | Amount of formulated product |
| ‡ | Restricted entry interval (REI) is the number of hours from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest. |
| 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. |