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Management of Dry Bean Root Rot in Minnesota
April 01, 2001

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Consuelo Estevez de Jensen, James E. Kurle,
and James A. Percich, Department of  Plant
Pathology, University of Minnesota

Bean root rot has become more severe in Minnesota. Yield losses of as much as 50% have been observed in fields in highly infested areas. In Minnesota, root rot is caused primarily by the fungus Fusarium solani f. sp. phaseoli in association with F. oxysporum and Rhizoctonia solani.  Increased root rot severity has been attributed to shortening of rotation intervals and use of susceptible cultivars.

We evaluated various combinations of a peat-based formulation containing Bacillus subtilis and Rhizobium, the standard seed treatment (SST) Captan plus Streptomycin and Lorsban and an untreated control. Two different B. subtilis strains (GBO3 and MBI600) alone or in combinations with R. tropici UMR1899 and R. etli RCR3622 were evaluated.  Plant stands in the field were significantly increased with B. subtilis GBO3 plus R. etli RCR 3622 as well as with the B. sutilis GBO3 plus R. tropici UMR 1899 combination (Table 1). When either Rhizobium strain UMR1899 or RCR 3622 was used as an inoculant disease severity (DS) was reduced when compared to the untreated control (Table 1). Bean yields from seed treated with B. subtilis GBO3 plus R. etli RCR 3622 were significantly higher than yields of either the untreated control or SST (Table 1). The SST was not effective in controlling root rot and yields were similar to those of the untreated control. Captan appears to have limited effectiveness against root rot because it does not provide protection as the root elongates.  Captan and Streptomycin may inhibit colonization by Rhizobia.  The use of the co-formulated biocontrols of B. subtilis and Rhizobium strains may be a good strategy to maintain sustainable bean productivity and reduce the use of chemical seed treatments. 

Table 1. Effect of seed treatments on bean root rot at Verndale, Minnesota



Treatments

Emergence
of plants

Disease
Severity
(1-9)

Plant Dry
Weight
(g)

Root Dry
Weight
(g)

Yield
lb/acre

Bacillus subtilis GBO3 +Rhizobium etli RCR 3622

 223 a*

3.8 c

37.7 ab

 6.1 a

 1,699 a

Bacillus subtilis MBI600

161 d

4.3 bc

57.5 a

5.1 abc

1,331 ab

R. etli RCR 3622

188 bc

4.1 bc

34.9 ab

3.1 d

1,334 ab

B. subtilis MBI600+ R. etli RCR3622

191 bc

4.4 bc

33.1 b

3.8 cd

1,333 ab

B. subtilis MBI600+ R. tropici UMR1899

 191 bc

 3.8 c

39.2 ab

 4.3 bcd

 1,491 ab

B. subtilis GBO3 + R. tropici UMR1899

 219 a

 4.0 bc

35.7 ab

 4.5 bcd

 1,458 ab

Rhizobium tropici UMR1899               

176 c

4.2 bc

29.0 b

5.1 abc

1,478 ab

B. subtilis GBO3

186 c

2.8 d

37.8 ab

3.6 cd

1,443 ab

Untreated control

183 c

5.4 a

36.6 ab

5.7 ab

1,293 b   

Captan+Streptomycin+Lorsban (SST)

207 ab

4.7 ab

34.1 ab

4.54 bcd

1,236 b


 

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Northarvest Bean Growers Association | 50072 East Lake Seven Road | Frazee, MN 56544
Ph: 218-334-6351 | Fax: 218-334-6360 | Email: nhbean@loretel.net