Dry Bean Disease Control Research Program for the Northern Plains
April 15, 2002
By Luis del Rio Medoza Dept. of Plant Pathology North Dakota State University
This is the first report of activities from Luis del Rio. Luis replaced J. Venette as the bean pathologist at NDSU in March of 2001.
White mold is one of the most serious diseases affecting dry bean production in the region. Two chemical control alternatives were evaluated in 2001. All experiments had four replications at each of two locations, Carrington and Oakes.
Foliar calcium applications -- Calcium has been proposed as an inexpensive alternative to control white mold. Foliar applications of calcium (sulfate and chloride), alone or in combination with one half of the recommended doses of thiophanate methyl (Topsin) were compared to current NDSU recommendations (two applications of 1.5 lb fungicide per acre during flowering). Results of these experiments were combined with data collected in experiments conducted between 1997 and 2000 at both locations.
The combined analysis indicated that calcium does not have an effect on incidence or severity of white mold, and does not increase yields. Applying one half of the recommended doses of fungicide alone had the same effect on white mold and yield than applying it in combination with calcium. Fungicide applications at the full- recommended rate (1.5 lb/acre) provided the best protection and highest yields in all years and environments.
Foliar applications of lactofen -- The herbicide lactofen has been associated with reduced incidence of white mold in soybeans when applied at flowering time. In 2001 two concentrations of two lactofen formulations (Cobra and Phoenix), applied at flowering time, were compared to Topsin applications.
Lactofen applications provided protection levels similar to that produced by Topsin applications, and significantly better than the untreated controls. However, no differences in yield were detected. Experiments to be conducted in 2002 will be oriented to optimize the benefits of lactofen by reducing the amount of tissue burnt while keeping the same level of protection.
Race 73 of dry bean anthracnose (Colletotrichum lindemuthianum) (Figure 1) was detected for the first time in commercial fields in seven North Dakota counties in 2001. Thirty of the most popular cultivars planted in the region were screened for their reaction to this race. All pinto beans, including Maverick, and one half of the navy beans evaluated, including Norstar, were highly susceptible. All kidney beans were resistant. Intense efforts are being dedicated to screen the advanced lines from the breeding program to identify resistant materials. Such activities will continue in 2002.
A complex of soil fungi are responsible for root rots. Isolates of Rhizoctonia solani and Fusarium solani have been obtained and preliminary trials are in progress to develop an inoculation technique that will allow us to screen materials in the greenhouse during the winter. Experimental products were evaluated as seed treatments and foliar applications to control root rots in Fargo during 2001, but without positive results. Seed treatments will be evaluated again in the 2002 season.
No rust epidemics were detected in fields in 2001. Rust isolates collected between 1995 and 2000 were inoculated in sets of differential cultivars to identify the races present. This is the first time the race composition of bean rust is characterized in North Dakota. Five races were identified, 52, 54, 69, 70 and 71. Race 54 was the most prevalent, being retrieved from 90% of the collections evaluated. This information will be used to redirect breeding efforts and to conduct genetic studies on rust resistance.
A complex of three bacterial diseases are grouped under this category. A total of 161 isolates of the species that causes halo blight (Pseudomonas syringae pv. phaseolicola), collected between 1995 and 2000 at several bean fields in North Dakota, were inoculated on a set of eight differential cultivars in order to identify the races present. Races 6 and 2 were identified. Race 2 constituted less than 2% of the isolates evaluated and could be an indication of a recent introduction. Over 90% of the isolates were identified as race 6. Race 6 is also present in other midwestern states. This is the first report on halo blight race identification in North Dakota. This information will be provided to the breeding program for future germplasm screenings.