Go Back to Garlic Rust
Outbreak in California
Kern County Garlic Rust Trial - 1998
Joe Nunez, Farm Advisor
UCCE Kern County
Garlic rust is usually a disease of only minor concern in California. It appears sporadically in the state, but generally causes little damage. This year, however, garlic rust has appeared in several garlic growing areas of the state as a serious pest problem. In Kern County, the amount of infection varies widely from field to field with only a few fields particularly hard hit with this disease.
Garlic rust, caused by the fungus Puccinia porri, can also infect onions and other Allium species. However, in California it is usually found only on garlic and rarely on onions.
Infection begins as small light colored spots on the leaves that later enlarge to become orange pustules filled with spores. These orange spores from within the pustules are easily rubbed off. The leaves of infected plants become yellow and eventually senesce prematurely as the disease progresses. The older outer leaves show symptom's first and are more heavily infected than the younger inner leaves. As the disease progresses further, a second type of spore is produced. When this occurs, the orange pustules become black and dark colored spores are then produced.
Several fungicide trials are in various stages of completion by UCCE researchers to determine which fungicides are most effective for the control of garlic rust. From the trial conducted in Kern County, chlorothalonil and metalaxyl/mancozeb appear the materials of choice. Neither material provides complete control, but they are effective in protecting the new leaves and slowing the progress of the disease. Copper hydroxide and sulfur fungicides provide little or no protection from this particular disease. These materials may need to be applied on a 7 to 10 day schedule, depending on rate of growth, amount of rainfall, and if sprinkler irrigation is used.
Results
|
|
Leaf Infection |
Top Weight (Kg) |
| 1 |
Control |
3.2 |
0.45 AB |
| 2 |
Ridomil/MZ 2.5 lb/A |
1.8 |
0.48 AB |
| 3 |
Bravp 720 3 pt/A |
2.2 |
0.54 A |
| 4 |
Thiolux 10 lb/A |
3.1 |
0.45 AB |
| 5 |
Kocide DF 2 lb/A |
3.0 |
0.40 B |
| 6 |
Manex 2.4 qt/A |
1.9 |
0.52 AB |
|
|
P=0.09 |
P=0.055 |
|
|
|
LSD,0.05=0.095 |
This page was updated on Monday March 17 2008
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