Oakes Irrigation Research Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701) 742-2700, email: rgreenla@ndsuext.nodak.edu

 

Control of White Mold in Dry Beans using Topsin and Lactofen

Luis del Rio and Pat Gross

Department of Plant Pathology, NDSU


Results summary

Table 59. Schedule of applications of two formulations of thiophanate methyl

Table 60. Schedule of applications of two formulations of lactofen

Table 61. Effect of two formulations and two doses of thiophanate methyl on control of white mold

Table 62. Effect of different formulations and doses of lactofen on control of white mold


          Two studies were conducted at the NDSU Oakes Irrigation Research Site in the 2002 season. The first study compared the effectiveness of two doses of a new formulation of thiophanate methyl (Topsin) vs. two doses of the current commercial formulation (wettable powder) for control of white mold (Table 59). The second study compared the effectiveness of three doses of the herbicides Cobra and Phoenix as indirect methods for control of white mold (Table 60). Both experiments used a randomized complete block design with four replications. Each experimental plot had four rows 20 feet long planted to cv. ‘Buster’ at a density of 82,000 seeds per acre. Each row was planted 30 inches apart. Phytotoxicity of the herbicides, white mold incidence, white mold severity and yield were recorded from the two center rows. Weeds were controlled with Basagran, mechanical cultivation, and hand weeding. At flowering time, 250 ml of a 104 ascospore suspension was sprayed on the center two rows of each experimental plot. Fungicides were mixed with water buffered at pH 7.0 in Fargo and applied within 2 hours using a CO2 backpack sprayer. The sprayer was equipped with drop nozzles on a 10 ft boom set up to deliver 37 gal/acre at 35 psi.

          Twenty randomly selected plants from each experimental plot were evaluated for white mold incidence and severity on July 26 and Aug 9. Severity was evaluated using a 0 to 5 scale where 0 = 0%, 1 = 5%, 2 = 15%, 3 = 40%, 4 = 65%, and 5 = 85% or more of plant tissues infected. Phytotoxicity was measured as the proportion of canopy reduction of treated plants compared to the untreated plot in each replication. The center two rows of each plot were harvested on Aug 27. Beans were dried in forced air driers at 120 °F for approximately 5 days. Yields were expressed in pounds per acre at 8% moisture content. Statistical analysis was conducted using Proc GLM (SAS package). Probability levels of P=0.05 were used for all evaluations. LSD values were calculated and used for mean comparisons for incidence, severity and yield.


RESULTS


          White mold did not develop as aggressively as in previous years despite the ascospore inoculation and the continuous irrigation of experimental plots during and after flowering. Hot weather at flowering time slowed down white mold development. By the first week of August, white mold incidence was at almost one half of what is usually seen in these kinds of trials at Oakes. The new formulation, TD-244701, at both rates was as effective as the commercial bag formulation in controlling white mold. Untreated controls had a final white mold incidence of 33% with a severity of 17%. No differences in yield were detected among treatments (Table 61).

          A similar situation was observed in the lactofen study. The low disease pressure observed did not reduce yields significantly in the untreated control compared to plots protected with Topsin 70 WP. Likewise, plants treated with 2 or 3 fl oz of Phoenix had significantly less white mold incidence and severity than the untreated plots but similar yield (Table 62). The application of 1 fl oz of Phoenix/acre resulted in significantly less toxicity compared to other herbicide treatments, but did not result in less white mold or higher yields.

          This is the second season of evaluation of lactofen (as Phoenix or Cobra) for control of white mold on dry beans. In both seasons less disease was observed in herbicide-treated plots compared to the untreated controls, but these differences did not translate into higher yields. However, the yield gap between herbicide treated and untreated plots has been reduced from 2001 to 2002. Additional changes and fine tuning is required to optimize the use of lactofen as an alternative option to manage white mold on dry beans. We plan on continuing evaluating lactofen in future field and greenhouse studies.


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Table 59. Schedule of applications of two formulations of thiophanate methyl for control of white mold on dry beans.

Treatment

Rate/acre

Schedule

Untreated check

 

 

Topsin 70 WSB

1.5 lb

Single application at 100% bloom

Topsin 70 WSB

1.0 lb

First application at 20-30% bloom, second application 7 days later

TD-2447-01

32.0 oz fl

Single application at 100% bloom

TD-2447-01

21.3 oz fl

First application at 20-30% bloom, second application 7 days later


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Table 60. Schedule of applications of two formulations of lactofen for control of white mold on dry beans.

Treatment

Rate/acre

Number of applications

Schedule

Phoenix

1 fl oz

1

pre-bloom

Phoenix

2 fl oz

1

pre-bloom

Phoenix

3 fl oz

1

pre-bloom

Cobra

2 fl oz

1

pre-bloom

Cobra

3 fl oz

1

pre-bloom

Topsin 70 WP

1.5 lb

1

20-30% bloom

Untreated control

 

 

 


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Table 61. Effect of two formulations and two doses of thiophanate methyl on control of white mold on dry beans.

Treatment

Rate

Incidence1

Severity2

 

7/26

8/5

7/26

8/5

Yield3

 

 

-------------------- % --------------------

lbs/acre

 

Untreated check

 

10

33

13

17

2933

Topsin 70 WSB

1.5 lb

12

19

9

16

2988

Topsin 70 WSB

1.0 + 1.0 lb

12

24

7

10

2978

TD-2447-01

32 fl oz

2

18

5

14

2881

TD-2447-01

21.3 + 21.3 fl oz

8

21

6

17

2967

 

LSD (P=0.05)

10

13

2

10

257

1 Incidence based on number of infected plants divided by total number of observations.

2 Severity is based on average percentage disease of infected plants.

3 Yield expressed at 8% moisture content.


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Table 62. Effect of different formulations and doses of lactofen on control of white mold on dry beans.

Treatment

Rate

White mold (Aug 5)

Herbicide phytotoxicity

Dry bean

yield3

Incidence1

Severity2

8/8

8/15

 

 

--------------------------- % --------------------------

lbs/acre

 

Phoenix

1.0 fl. oz

25.0

5.8

18.8

12.5

2947

Phoenix

2.0 fl. oz

16.3

2.3

25.0

16.3

2833

Phoenix

3.0 fl. oz

18.8

2.3

25.5

22.5

2687

Cobra

2 fl oz.

37.5

7.7

21.3

17.5

2795

Cobra

3 fl oz.

31.3

6.2

22.5

15.0

2875

Topsin 70 WP

1.5 lb

30.0

6.8

0.0

0.0

3005

Untreated control

 

36.3

8.2

0.0

0.0

2882

 

LSD (P=0.05)

13.9

5.1

5.4

5.9

396

1 Incidence based on number of infected plants divided by total number of observations.

2 Severity is based on average percentage disease of infected plants.

3 Yield expressed at 8% moisture content.


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