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Project Abstract: Managing Pests in Dry Bean

Dry bean (Phaseolus vulgaris L.) has several fungal, insect and bacterial pests that cause serious damage to yield and seed quality. Since dry bean is typically consumed with minimal processing, visual seed quality is very important.

The goal of this project is to evaluate the efficacy of new pest control options, and to develop a comprehensive management strategy for each pest. Once sufficient efficacy data has been collected, the economic impact of each new control product is determined. This is a key component, so growers make correct management decisions. Individual trial summaries are published on-line at: http://www.ridgetownc.uoguelph.ca/research/documents/gillard_Dry_Bean_Annual_Research_Report_2017.pdf

Two key fungal pests of dry bean are anthracnose (Colletotrichum lindemuthianum) and white mold (Sclerotinia sclerotiorum). Genetic resistance and cultural management play a role, but foliar fungicides are a key component to manage each pest. Research is conducted each year to evaluate new foliar fungicides for efficacy. In 2016, a total of 19 and 17 treatments evaluated for anthracnose and white mold, respectively, using small plot replicated field experiments. There was unusually low disease pressure for all studies in 2016, due to high temperature during the infection period. This underlines the importance of developing a long term data set, as conditions for disease expression can vary dramatically from year to year. Long term data from 11 white mold studies over 5 years (2011-2015) is currently being compiled, to provide further evidence of the long term efficacy and economics of key fungicide products. A new study in 2016 investigated the impact of row width/plant population on white mold disease pressure in a dry bean canopy. This research ties in nicely with leading edge production practices, as growers are currently experimenting with variable plant populations on a field scale, to manage white mold. A refereed publication on foliar fungicide performance for anthracnose is anticipated, following the completion of field studies in 2017.

Common bacterial blight (CBB, Xanthomonas axonopodis pv. phaseoli) is a prevalent foliar pest of dry bean, causing yield losses up to 21% (Can. J. Plant Sci. 89:405-410). Plant breeders have worked extensively on genetic resistance for 15 years. Given the rate of cultivar development and grower uptake, it will take many years before genetic tolerance will have a large impact on this disease. This is particularly evident in the large seeded market classes, which are considered more susceptible than small seeded classes to CBB. Cultural methods including the production of ‘disease-free’ seed in dry land regions of the U.S. (e.g. Idaho) is the key for CBB management. This project looks at new foliar and seed treatment controls for CBB, as alternative control measures. Several compounds have been identified that can impact the pest, but none provide season-long disease control. In 2016, four new compounds were evaluated in navy and kidney beans.

Root rot is the largest pest of dry bean, with Fusarium spp. and Rhizoctonia spp. being the most common organisms. Genetic and cultural controls do not have a large impact, while chemical controls (e.g. fungicide seed treatments) protect seedlings only for a few weeks after planting. Commercial dry bean seed typically has 4 or more fungicide seed treatments applied, with almost 100% of the seed lots treated. A number of new seed treatment compounds are available, so there are a several possible combinations to manage each fungus. This project measures the efficacy of new control measures for Fusarium spp. and Rhizoctonia spp. In 2016, several treatments increased plant stand by 50% and plant vigour by 40% at 4 weeks after planting, compared to an untreated control. This resulted in yield increases of 100% or more. Synergy has been measured repeatedly between some compounds (e.g. sedaxane and ipconazole), which is important information to develop commercial seed treatment formulations. Although seed treatments only provide short term control of root rot, maintaining early season plant health and strong plant stands are important considerations for high yielding crops.

Soybean Cyst Nematode (SCN) is the largest pest of soybean in North America. Dry bean is an alternate host to SCN, and the threat to commercial bean production has been largely ignored. In dry bean, there are no clearly defined control measures. Genetic resistance is not understood. Several chemical and biological controls have recently been registered for other field crops, but have not been evaluated on dry bean. These controls may play a key role in managing SCN, particularly when soybean and dry bean are both present in a crop rotation. Field based SCN studies were conducted by a grad student (X. Zhang), but variations in pest populations and environmental conditions resulted in few treatment differences. Controlled environment studies have commenced with a grad student (W. Zhang), and preliminary results demonstrate much less variability in treatment performance. Other graduate student projects should come on line in 2017. The first will evaluate new biological and chemical seed treatments to manage SCN. A second study will determine the tolerance of dry bean cultivars and market classes to SCN.

 

Project lead: Chris Gillard (519) 674-1500 Ext 63632 Cgillard@uoguelph.ca

 

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