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HPIPM:Rust
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Author: Howard F. Schwartz, Gary D. Franc & Eric D. Kerr
HPIPM:Home > Crops > Dry Beans > Rust
rust
Photo by Howard F. Schwartz, Colorado State University, Bugwood.org
Taxonomy
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Fungi
Basidiomycota
Urediniomycetes
Uredinales
Pucciniaceae
Uromyces
appendiculatus
Scientific Name
Uromyces appendiculatus
F. Strauss
Scientific Name Synonym
Uromyces phaseoli
G. Winter
Contents
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1 Part of Plant Affected
2 Symptoms and Damage
3 Factors Favoring Disease Development
4 Management Approaches
Part of Plant Affected
Leaves, stem, pods
Symptoms and Damage
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.
Factors Favoring Disease Development
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.
Management Approaches
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
Application
Acre (ai oz) Frequency (days)
PHI, remarks
Bravo 720#1, (DF)
22-32 fl oz
7-10
Terranil 6L (90DF)
(11.9-17.3)
(Colorado 24(c)).
Do not feed
debris.
Endura (Boscalid)
8-11 oz
Folicur 3.6F
(Tebuconazole)
4-6 fl oz
14
Maximum of 12 fl oz; 14 day PHI
Headline
6-9 oz
7-14
Never apply in sequential
applications. Max of 2 times per
season; 21 days PHI.
Maneb 80W
1.0-2.0 lb
5-7
30 days PHI
14 days PHI
Maximum of 2 applications (22 oz)
/season; 21 days PHI
Maneb 75DF
Maximum of 12 lbs
Manex
38-51 fl oz
(14-18.9)
5-10
Maximum of 19 pt ; 30 days PHI
Proline 480SC
5.7 fl oz
5-14
Begin at first signs of disease,
(Prothioconazole)
Maximum of 3 applications (17.1 fl
oz); 7 day PHI
Quadris
6 fl oz
7-14
Super Six
64-128 fl oz
7-14
Top Cop+S
64 fl oz
(37.1)
1
14 days PHI
1 day PHI
Labeled for chemigation
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 is 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 your State Department of Agriculture for the rules, regulations and allowances applicable in your state
and locality.
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