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United States Department of Agriculture

Agricultural Research Service

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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

2012 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:

A 9-cultivar trial found that Eckes 1201 and Hunky Dory remained healthy. A 15-cultivar trial in progress is being complicated by the excessive summer heat. Five genera were inoculated with 6 Phytophthora spp. Drendranthema xgrandiflorum ‘Alcala Red’ (chrysanthemum, Asteraceae) did not develop disease. P. citricola, P. drechsleri were most virulent on Osteospermum ‘Soprano Purple’ (Asteraceae). P. nicotianae, P. cryptogea, P. citricola, P. drechsleri were most virulent on Lathyrus odoratus ‘Incense Mix’ and P. drechsleri on Lupinus polyphyllus ‘Russell Mix’ (both Fabaceae). P. cryptogea, P. dreschleri were most virulent on Calibrachoa xhybrida ‘Cabaret Red Improved’ (Solanaceae). P. cactorum and P. capsici were included in the experiment. Six cultivars of Osteospermum (Asteraceae) were evaluated for susceptibility to P. drechsleri. Sunny Olivia was statistically similar to Sunbrella Taurus (no plant death); all Soprano plants died. Although virulence of Phytophthora spp. differed within crops, symptoms were similar. Dendranthema was not infected. Our efficacy trials supported 24(c) Special Local Needs labeling of Subdue and Quadris in MI, CA, AL, TX and FL, and Section 18 labeling of Revus, Ranman in CA, AL and TX for greenhouse basil downy mildew. MILESTONE C1. Screen active ingredients to identify those with potentially useful activity against each pathogen. Ten efficacy trials tested 32 products (4 biopesticides, 10 reduced risk fungicides, 5 experimentals, 13 industry standards and other chemistries). Trials included downy mildew-basil, Phytophthora-calibrachoa, Botrytis-poinsettia, Pythium-poinsettia (2 trials), downy mildew-impatiens (2 trials), powdery mildew-petunia (2 trials), and Rhizoctonia root rot-pansy. In the initial screening and characterization tests, products will be tested using one susceptible crop per pathogen. Dosages, application intervals, and drenches vs. foliar sprays were tested in 7, 4, and 1 trials, respectively.


Last Modified: 8/19/2014
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