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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Employing New Tools to Detect and Limit Phytophthora Root Rot, Downy Mildew, and Other Key Pathogens of Floral Crops

Location: Biological Integrated Pest Management Unit

2011 Annual Report


1a.Objectives (from AD-416)
Greenhouse-grown floral crops are constantly threatened by a great variety of pathogenic microorganisms and arthropod pests. Growers need integrated management strategies incorporating cultural practices and a wide variety of effective pesticides to grow a quality crop at a reasonable price. Reduced risk and biological pesticides with novel/unique modes of action are particularly needed for rotation schemes designed to manage resistance and reduce inputs of hazardous chemicals into the environment.

The overall objective of this cooperative research project is to develop new technologies and strategies for more effective management of diseases and insect pests of greenhouse floriculture crops. Specific objectives are to:.
1)determine the susceptibility among coleus cultivars to downy mildew;.
2)determine the host range and virulence of Phytophthora species that may infect floral crops within the Asteraceae, Fabaceae, and Solanaceae families;.
3)characterize the efficacy of new active ingredients, including reduced-risk fungicides, biocontrol agents, and biopesticides, against Botrytis cinerea, Phytophthora spp. (specifically to include P. cactorum, P. capsici, P. citricola, P. cryptogea, P. drechsleri, P. nicotianae, P. tropicalis), Pythium spp., Rhizoctonia solani, Thielaviopsis basicola, downy mildew and powdery mildew pathogens; and.
4)improve the integration of foliar plant disease management practices with biologically-based IPM programs being developed for insect pests.


1b.Approach (from AD-416)
Project objectives will be accomplished through establishment of an interdisciplinary research team that will pursue project objectives within the framework of our existing plant pathology research programs. Research will be conducted through close interaction with diverse growers throughout the United States. Research on new active ingredients and commercial products (including reduced risk fungicides and biopesticides) for control of Botrytis, Phytophthora, Pythium, Rhizoctonia, Thielaviopsis, downy mildew and powdery mildew pathogens will focus on identification of the most effective materials and determination of application rates, application intervals, and other factors that provide for highest and most consistent and reliable efficacy. Efficacy tests will be conducted in replicated research plots using susceptible crops. In collaboration with USDA-ARS researchers at Ithaca, NY, laboratory assays and small-scale greenhouse tests will assess compatibilities among fungicides used for control of foliar plant diseases and beneficial fungi (mycoinsecticides) used for insect pest management.


3.Progress Report

Objective 1. Determine the susceptibility of coleus cultivars to downy mildew. Two screens were completed, one of 13 and the other of 17 cultivars. Susceptible ‘Volcano’ and ‘Dragon Black’ were included in each trial.

Objective 2. Determine the host range and virulence of Phytophthora species that may infect floral crops within the Asteraceae, Fabaceae, and Solanaceae families. Two genera of Fabaceae (Lathyrus latifolius, Lupinus polyphyllus) and five of Solanaceae (Browallia speciosa, Calibrachoa xhybrida [2 cultivars], Nicotiana xsanderae, Nierembergia scoparia, Petunia xhybrida) were evaluated for susceptibility to one isolate of P. tropicalis and four isolates of P. capsici. Six cultivars of Calibrachoa xhybrida were evaluated for susceptibility to one P. tropicalis and one P. capsici isolates. Phytophthora-infected Lathyrus, Lupinus, Calibrachoa and Nicotiana exhibited varying disease symptoms, which were evaluated and recorded. Plants inoculated with P. tropicalis or P. capsici exhibited similar symptoms. No symptoms were observed on Browallia, Nierembergia or Petunia.

Objective 3. Characterize the efficacy of new active ingredients, including reduced-risk fungicides, biocontrol agents, and biopesticides against Botrytis cinerea, Phytophthora spp., Pythium spp., Rhizoctonia solani, Thielaviopsis basicola, downy mildew, and powdery mildew. Efficacy trials carried out in FY 2011 tested 33 products and included powdery mildew of calibrachoa (2 trials), downy mildew of coleus and of basil, Pythium root rot of geranium, Botrytis blight of poinsettia, Thielaviopsis root rot of pansy, Phytophthora root rot of osteospermum, and three trials of Rhizoctonia root rot of zinnia.

Technology transfer. Research advances were disseminated to agricultural extension scientists and commercial growers, and recommendations for effective use of novel control agents were formulated and made available to product manufacturers, growers, and agricultural researchers. As of June 1, 17 articles (6 extension, 5 Plant Disease Management Reports, 4 magazine, 2 proceedings) have been published and 7 presentations made at 2 international, 1 national and 4 Michigan growers meetings.

Project activities have been monitored by the ADODR via telephone conversations and e-mail communications with MSU.


Last Modified: 10/25/2014
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