Uromyces appendiculatus
Leaves, stem, pods
Rust symptoms first appear on the upper and/or lower surfaces of leaves as small yellow or white slightly raised spots. Green pods, and occasionally stems, also may become infected and develop typical rust pustules. These spots enlarge and raise further to form reddish-brown or rust-colored pustules which are about 1/8 inch diameter and contain thousands of microscopic spores called urediniospores (summer spores) which allow the fungus to spread within and between fields. Pustules may be surrounded by a yellow border. Spores are readily released from the pustule and give a rusty appearance to anything they contact. Spores feel like talcum powder when rubbed between the fingers. Severe infection results in premature leaf drop. Pod set, and especially pod fill, can be reduced if infection is severe during early reproductive development of the bean plant. Near the end of the season, many pustules change color, and form dark brown to black teliospores (winter spores) which allow the fungus to overwinter in some production areas.
Rust reoccurs next spring when teliospores germinate to form basidiospores which then infect volunteer beans. Infected plants produce pycnia (yellow blisters on the upper leaf surface) and aecia (white cups) on the lower leaf surface or stems near the soil line. Aeciospores move with the wind currents and infect new crop bean plants, resulting in summer spore production. Summer spores are produced in repeating cycles of progressive disease development throughout the summer. Summer spores are moved long distances (regionally) by wind.
Rust development is favored by cool to moderate temperatures less than 86° F with moisture conditions that result in prolonged periods of free water on the leaf surface. Repeating cycles of summer spore development may occur at 10 to 14 day intervals under favorable conditions. The earlier plants become infected during development, the greater the potential for yield loss. Anything that delays plant maturity, such as hail damage, excess nitrogen, or late planting increases the potential for significant yield loss in the event that environmental conditions favor a rust epidemic.
1. Plant certified seed of varieties resistant to the prevalent races of rust in the area.
2. Avoid the use of susceptible varieties, especially when planting after June 25, since plants may be exposed to more spore pressure from earlier maturing fields during late August and early September.
3. Incorporate infected bean debris into the soil after harvest and rotate with non-host crops for at least two years. Eliminate volunteer beans the following season.
4. Monitor fields frequently during blossom and early pod development for the initial signs of rust, especially if daily high temperatures are less than 86° F and there is more than 0.25 inches of rainfall per week.
5. Fungicides that prevent or reduce rust infection are more effective when applied early in the epidemic. Thorough coverage is essential.
Moderately to severely rusted bean plants require twice as much moisture from irrigation as uninfected plants to maintain pod set and seed fill.
Products for Rust:
Fungicide Common/Trade Name |
Product per Acre (ai oz) |
Application Frequency (days) |
PHI, remarks |
|
Bravo 720#1, (DF) Terranil 6L (90DF)
|
22-32 fl oz (11.9-17.3)
|
7-10 |
14 days (Colorado 24(c)). Do not feed debris. |
|
Endura (Boscalid)
|
8 – 11 oz/A |
|
21 days. Max of 2 times (22 oz) /season |
|
Headline |
6 – 9 oz |
7-14 days |
21 days to harvest. Never apply in sequential applications. Max of 2 times per season. |
|
Maneb 80W Maneb 75DF |
1.0-2.0 lb/ A
|
5-7 |
30 days, maximum of 12 lbs |
|
Manex
|
38-51 fl oz (14-18.9)
|
5-10 |
30 days, maximum of 19 pt |
|
Quadris |
6 fl oz |
7-14 days |
14 days to harvest |
|
Super Six |
64-128 fl oz (-) |
7-14 |
|
|
Top Cop+S |
64 fl oz (37.1) |
- |
1 day |
|
1Labeled for chemigation |
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed in neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact you State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Dry beans, Diseases, Rust
Date: 06/13/2007