Symptoms and Signs
Symptoms are usually not apparent until heading. Smutted heads usually emerge earlier than healthy heads. Diseased heads consist of olive-black masses of spores, called teliospores, in the place of kernels. The smut spores are enclosed in a fragile, gray membrane that soon ruptures to release the airborne spores. By the time the grain matures, the spores are dispersed, leaving only a bare rachis.
Comments on the Disease
Most loose smut pathogens survive from one season to the next as dormant mycelium inside infected seed. The fungus that causes false loose smut survives as teliospores on the surface of contaminated seed. The false loose smut strains that infect oats are different from those that infect barley. False loose smut of barley and oats was formerly called black loose smut.
Management
Cultural Control
Use certified smut-free seed. A hot water treatment can eliminate smut fungi from contaminated seed, but it must be used carefully to avoid reducing seed vitality. For information on hot water treatments, see UC ANR Publication 3333, Integrated Pest Management for Small Grains.
Chemical Control
Systemic fungicides are necessary when treating seed because loose smuts are borne internally in seed.
| Common name | Amount per 100 lb of seed | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are listed alphabetically. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, resistance risk, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| SEED TREATMENT | ||||
| CARBOXIN | ||||
| (Vitavax-34) | Label rates | 12 | NA | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Carboxamide (7) | ||||
| COMMENTS: This product is not labeled for use in California, but seed treated in and obtained from another state can be legally used in California even for a pesticide not registered on small grains in California. Contact your retail seed dealer for information and availability. For use on barley, oats, triticale, and wheat. Do not use treated seed for food, feed, or oil purposes. Do not graze or feed livestock on treated areas for 6 weeks after planting. | ||||
| DIFENOCONAZOLE/MEFENOXAM | ||||
| (Dividend Extreme) | Label rates | 48 | NA | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)/phenylamide (4) | ||||
| COMMENTS: For use on wheat, triticale, and barley. Do not use treated seed for food, feed, or oil purposes. Do not graze wheat or triticale forage for 55 days after planting and barley for 30 days after planting. Do not plant any crop other than those listed on the label within 30 days to fields in which treated seed was planted. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. 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 different group numbers are suitable to alternate in a resistance management program. In California, make no more than one application of a fungicide with a mode-of-action group number associated with high resistance risk before rotating to a fungicide with a different mode-of-action group number; for other fungicides, make no more than two consecutive applications before rotating to fungicide with a different mode-of-action group number. |
| NA | Not applicable. |
Text Updated: 04/26
Treatment Table Updated: 07/25