Dry Bean Disease Control Research Program for the Northern Plains 2003
April 13, 2004
White mold: Lactofen (Phoenix) applied at 0.5 oz/A two weeks prior to flowering reduced white mold incidence on dry beans significantly (P=0.1) compared to the untreated control at Carrington. However, the numerical yield difference between lactofen and untreated plots (2171 vs 1985 lb/A, respectively) was not statistically significant. The experiment will be repeated in 2004. Experimental plots at Carrington and Mapleton, treated with Intercept at 1 or 2 lb/A in 2001, were planted to dry beans and sunflower in 2003. Intercept, a biofungicide recently introduced to the US market, is made out of spores of the fungus Coniothyrium minitans. This fungus destroys the sclerotia of the white mold pathogen before it can produce apothecia and spores to attack dry bean flowers. Sunflowers were planted along with dry beans because they can be attacked by sclerotia that germinate in the ground producing mycelium instead of apothecia. In this way, sunflowers are better bio-indicators of the presence of sclerotia in the ground. The mean incidence of Sclerotinia wilt of sunflower was reduced from 12% in 2002 to less than 2% in 2003; white mold did not develop on beans in 2003. Laboratory tests indicated that by the fall of 2002 Intercept had already invaded untreated plots and was attacking between 35 and 60% of the sclerotia used in the study. Samples taken in the fall of 2003 showed that Intercept was still active in the soil affecting between 5 and 35% of the sclerotia incubated in such samples. These results suggest that Intercept could be a valid alternative for white mold management. Additional fields will be sought in the 2004 season to provide confirmation of these results.
Anthracnose: Over 100 fields in 12 North Dakota counties were surveyed for presence of anthracnose in 2003. The disease was detected in only three fields, but was also observed in two Minnesota fields. Most cases were tracked back to use of infected seeds. All isolates belong to race 73. Several isolates retrieved from seed samples processed by the North Dakota State Seed Department are currently being evaluated. Collaborative efforts with NDSU bean breeding program to identify breeding lines with resistance to anthracnose continued in 2003. Resistant materials are being identified an advanced. Collaborative efforts will continue in 2004.
Root rots: Cold and rainy weather prevailed in late May and early June delaying planting and seedling emergence in several areas of the Red River Valley; as a consequence, root rots heavily affected some areas. A couple of studies conducted in the 2003 season evaluated the efficacy of seed treatments with Captan and Bacillus spp., a biocontrol agent, for control of root rots. Both treatments increased yields significantly, when compared to untreated plots under heavy root rot pressure. However, yields were very low due to excessive rain early in the season. This study will be repeated in 2004.
Rust: Out of 90 fields surveyed in 2003 in the Red River Valley area, only a handful, located in Pembina and Grand Forks counties, developed bean rust. Rust was detected in Navigator and Pintoba beans, but not on Norstar or Maverick. We will continue monitoring fields in the 2004 season. Since section 18 was not available for Tilt, and concerns have been raised regarding the efficacy of the new chemistries for rust control, a fungicide trial will be established in the 2004 season to compare these chemistries to Tilt.