White mold (WM) is a serious disease of snap beans and other vegetable crops in Oregon and nationwide. Fields with >6% infected bean pods are rejected by the processor. Ronilan, a highly effective fungicide, is no longer available, and alternative WM management was the top research need identified in the 2005 snap bean pest management strategic plan.
The objectives of this project were to 1)engage conventional/organic processed/fresh market vegetable growers in development, implementation and evaluation of white mold management tools and systems management planning, 2) investigate biological, cultural and integrated white mold management strategies, 3) demonstrate effective white mold management strategies with and to growers to facilitate adoption, and 4) disseminate project results to a wider audience of farmers and agricultural professionals.
The project demonstated that low rate applications of Contans (Coniothyrium minitans) in combination with a moderately resistant bean cultivar, reduced tillage, and a three-year rotation out of a host crop could be used as a low cost strategy to reduce white mold risk in a rotational system. Farmers and agricultural professionals were engaged with project findings through presentations at Oregon Processed Vegetable Commission meetings, grower meetings and a field day, as well as through two articles published to oregonvegetables.com. Project findings were extended to IPM and horticultural professionals through poster presentations at professional meetings. An eOrganic webinar will be presented in March 2014.
1) Engage conventional/organic processed/fresh market vegetable growers in development, implementation and evaluation of white mold management tools and systems management planning.
2) Investigate biological (Contans), cultural and integrated white mold management strategies.
3) Demonstrate effective white mold management strategies with and to growers to facilitate adoption.
4) Disseminate project results to a wider audience of farmers and agricultural professionals.
White mold is a serious disease of snap beans and other vegetable crops in Oregon and nationwide. Fields with >6% infected bean pods are rejected by the processor. Ronilan, a highly effective fungicide, is no longer available, and alternative white mold management was the top research need identified in the 2005 snap bean pest management strategic plan. A stakeholder group formed the Willamette Valley Bean Mold Task Force (BMTF) to identify solutions to this problem. In 2005, the BMTF demonstrated that two applications of Topsin/Rovral or Topsin/Endura effectively controlled the disease but are considerably more expensive. Farmers and processors are participating in sustainability and organic certification programs requiring progress in bio-intensive IPM. Fresh market organic vegetable and seed farmers grow many vegetable crops susceptible to white mold, and management strategies are limited.
This project evaluated the use of Contans (biological control agent Coniothyrium minitans) alone and in combination with reduced tillage, moderately resistant bean cultivars, and rotation for the management of white mold of snap bean.
Objective 1) Project farmers worked closely with project staff to develop and deliver project activities.
Exp. 1. A 90A commercial fall cauliflower crop infested with white mold (causal agent Sclerotinia sclerotiorum, Ss) was flailed in November 2007; Contans (2 lbs/A) was applied to the decomposing residues. Lab-grown sterile sclerotia were placed in bags (15 per bag), fixed to the soil surface with flags four times over 10 months, and removed one to three months later; after removal, sclerotia were washed, surface-disinfected, and plated to determine viability and colonization by the biocontrol fungus Coniothyrium minitans (C. minitans) and other fungi. (For more information and figures, see attached poster Experiment 1.)
Exp. 2. Eight snap bean 91G fields were planted in June 2009, inoculated with Ss, and flailed but not incorporated at bean maturity. Native sclerotia were collected from the soil surface of all fields in October, bagged (15 per bag), and replaced in each field on the surface and at 5.1 cm depth. Contans was applied to four of the fields at approximately 1.5lbs/A in early November. Bags were removed on six dates over two years and sclerotia were plated. Sclerotia developed on 2010 snap beans were collected after flailing; sclerotia were bagged and placed in field on surface and at five cm. Bags were collected three times in 10 months and sclerotia were plated. (For more information and figures, see attached poster Experiment 2.)
Exp. 3. Four treatments were applied at bloom to two bean fields (one with and one without a history of Contans): 1) water, 2) 1 lb/A Contans, 3) Contans/low rate Topsin and 4) high rate Topsin. White mold sclerotia were collected at harvest and evaluated for Cm colonization. (For more information and figures, see attached poster Experiment 3.)
Exp. 4. Snap beans 91G (susceptible to white mold) and OR-6230 (moderately resistant to white mold) were planted in a randomized complete block design (six plots of each variety in each of the eight fields, four of which had a history of C. minitans application). Pod disease incidence and foliar disease severity were evaluated at harvest. (For more information and figures, see attached word document Experiment 4.)
Objectives 3 and 4) See Publication/Outreach Section below
EXP. 1. Contans applications to sclerotia left on the soil surface ‘grew up’ C. minitans in the field and provided a long term reservoir of C. minitans (Cm) in the field.
EXP. 2. Sclerotia that developed on beans grown in fields with a recent history of Contans application were colonized by (and ultimately destroyed by) C. minitans even though Contans was not applied in that production season, due to the reservoir of C. minitans in sclerotia surviving in the field from historic bean crops and Contans applications.
EXP. 3. Contans applications during bean bloom were dramatically more effective in destroying sclerotia generated on the bean crop than applications to diseased residues after harvest; however, at-bloom applications are not currently a registered use of Contans. C. minitans destroys sclerotia more rapidly when introduced earlier in the process of white mold and sclerotia development on the plant.
EXP. 4. At harvest, pod white mold incidence in the control fields was approximately 17 and 11% in 91G and OR-6230, respectively, and 7 and 3%, respectively, in the Cm treatment fields. The lowest pod disease incidence was observed in the OR-6230 plants grown in Cm-treated fields
Contans in combination with a moderately resistant bean cultivar suppressed bean mold to a greater degree than either strategy employed alone. These strategies, in combination with reduced tillage and a three-year rotation out of a host crop, could be used to reduce white mold risk in a rotational system.
Low rate Contans in combination with a moderately resistant bean cultivar, reduced tillage and a three year rotation out of a host crop, could be used as a low cost strategy to reduce white mold risk in a rotational system.
Educational & Outreach Activities
Outreach: A group of 15 farmer and processor representatives discussed project findings and plans at Oregon Processed Vegetable Commission meetings in winters 2009-10, 2010-11 and 2011-12. In addition, 30 farmers and agricultural professionals walked the field trials and discussed the results at a 2010 summer field day at the OSU vegetable farm, and more than 150 growers and agricultural professionals learned about project findings at the Oregon Processed Vegetable grower meetings in January of 2010, 2011 and 2013. A workshop on farm systems analyses and systems soil/pest management was coordinated in February 2013.
Stone, A. and M. Miyazoe, 2012. Biological control of white mold of snap bean with low rate Contans application. National IPM Symposium 2012. Poster. Available at http://www.ipmcenters.org/ipmsymposium12/023_Stone.pdf.
Stone, A., M. Miyazoe, and A. Heinrich, 2013. Biological control of white mold of snap bean with low rate Contans application. ASHS abstract. Available at http://ashs.org/abstracts/2013/abstracts13/abstract_id_15868.html.
Stone, A., 2013. White mold of snap bean and other vegetable crops. Oregonvegetables. Available at http://horticulture.oregonstate.edu/content/white-mold-vegetable-crops
Stone, A., 2013. What is Contans and how can it be used to control white mold? Oregonvegetables. Available at http://horticulture.oregonstate.edu/content/what-contans-and-how-can-it-be-used-western-oregon-control-white-mold
An eOrganic webinar on the use of Contans in organic production systems was delivered in March 2014. Available as powerpoint file and webinar at http://www.extension.org/pages/69132
Journal articles are in preparation.
This project’s field experiments were not completed until summer 2013, so research results are only now being developed into outreach publications. Farmers are learning about how to incorporate Contans into systems management of white mold through workshops conducted as part of a new project “Integrating Research and Practice in Systems Management of Organic Farms.”