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How to Manage Pests
UC Pest Management Guidelines
Onion and Garlic
Rust
Pathogen: Puccinia porri
(Reviewed 1/07,
updated 1/07)
In this Guideline:
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Rust is primarily a disease of garlic, although onion, leeks,
shallots, and wild species of Allium are
hosts. Small, reddish to dull orange oval-shaped pustules develop on leaf
blades. Reddish airborne urediospores are copiously produced within the
lesions. Later in the growing season, the lesions may appear dark because black
teliospores develop within the pustules. Heavily infected leaves turn yellow
and may collapse prematurely. When infection is severe, bulb size and quality
are reduced.
Rust is a sporadic disease that generally causes little or no
economic damage. Since 1998, however, rust has caused severe damage in some
garlic-growing areas. Apparently, the disease only damages onions when they are
planted next to a heavily infected garlic field. The fungus probably
overwinters on garlic and volunteer Allium crops.
Rotate away from Allium crops
for 2 to 3 years and destroy volunteer Allium plants during this period. Fungicides may be
warranted if more than a few pustules develop on plants.
| Common name |
Amount/Acre |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
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| When choosing a pesticide, consider information relating
to environmental quality.
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| A. |
AZOXYSTROBIN |
| |
(Amistar) |
2–4 oz |
4 |
0 |
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(Quadris) |
6.2–12.3 fl oz |
4 |
0 |
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MODE OF ACTION: A QoI (Group 11)1 fungicide. |
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COMMENTS: Begin applications before disease development and repeat every 7–14 days up to 3 applications. |
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| B. |
MANCOZEB |
| |
(Penncozeb) 75DF |
2–3 lb |
24 |
7 |
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MODE OF ACTION: A QoI (Group 11)1 fungicide. |
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COMMENTS: Applied as a protectant and in mixes, or used in rotation with systemic fungicides for disease resistance management. |
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| C. |
MANEB 75DF |
2–3 lb |
24 |
7 |
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MODE OF ACTION: A multi-site contact (Group M3)1
dithiocarbamate fungicide.
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COMMENTS: Applied as a protectant and in mixes, or used
in rotation with systemic fungicides for disease resistance management. |
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| D. |
TEBUCONAZOLE |
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(Folicur) 3.6 F |
Label rates |
12 |
see label |
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MODE OF ACTION: A DMI (Group 3)1
triazole fungicide.
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COMMENTS: Use allowed under a Section 18; check with your County Agricultural Commissioner. |
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UC IPM Pest Management Guidelines: Onion and Garlic
UC ANR Publication 3453
Diseases
R. M. Davis, Plant Pathology, UC Davis
B. J. Aegerter, UC Cooperative Extension, San Joaquin Co.
Acknowledgment for contributions to the diseases section:
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara/San Luis Obispo counties
R. E. Voss, Vegetable Crops, UC Davis
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