Location: Horticultural Crops Disease and Pest Management Research Unit
Project Number: 2072-22000-045-062-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2025
End Date: Oct 31, 2026
Objective:
Plant health and profitability of flowering crops that are in demand by florists, landscapers and homeowners will be saved through developing biological-based control strategies to stop profit-stealing molds, mildews, root rot and leaf blights. The U.S. floriculture industry has a value of $6.7 billion annually. Michigan ranks third in production behind California and Florida and accounts for 10% of the nation's wholesale value of these floriculture crops. Our project will replace current chemical-dependent strategies with biocontrols and other novel strategies that are safe for producers and the environment while providing a high level of plant protection for a reliable and steady supply of U.S. product and decrease reliance on imports.
Specific objectives include:
Activity 1: Test new plant-protection products, including reduced-risk fungicides, biopesticides, and biocontrols against root rot (e.g. Thielaviopsis basicola, Rhizoctonia solani, Phytophthora spp., and Pythium spp.) and foliar spots (e.g. black spot), mildews (e.g. downy mildew, powdery mildew) and leaf mold (Botrytis blight). We will screen key active ingredients to evaluate efficacy against each pathogen. Dosages and application frequencies of active ingredients showing potential for disease suppression will be evaluated. In the initial screening products will be tested using one susceptible crop per pathogen.
Activity 2: Use whole-genome sequencing data to confirm B. cinerea is the dominant pathogen of Botrytis blight in ornamental greenhouses, evaluate genetic differentiation and population structure among hosts, greenhouses, growing cycles, and fungicide response phenotypes, and identify genomic regions associated with multifungicide resistance.
Activity 3: Provide results and recommendations directly to producers and allied industries via publication in trade magazines, website updates, and presentations. We will report directly to producers and allied industries via publication in trade magazines, website updates, and presentations.
Approach:
We will complete activities in close connection with U.S. growers to increase plant quality, health, and size for high profitability and increased domestic production. Our experienced team including a research technician, post-docs, graduate and undergraduate students will conduct controlled and replicated greenhouse studies to identify the leading biocontrol and other novel approaches for plant health. We will develop plant protection strategies for the highly destructive plant pathogens that cause root rot (Pythium, Thielaviopsis, Phytophthora, and Rhizoctonia), leaf mold (Botrytis) and mildew (powdery and downy), and leaf blights (black spot). The disease control studies that target the above-mentioned diseases and plant pathogens will be replicated and include varying application rates and intervals of natural plant protection products. To ensure reliable results for U.S. growers, our targeted studies will be conducted under different growing scenarios. Additional studies will be conducted on leaf mold (Botrytis) which is the second most destructive plant pathogen as it infects a high number of flowering and food crops. This leaf mold causes annual losses of up to $100 billion worldwide. We will use molecular approaches to advance our understanding of how this leaf mold can be best controlled in the U.S. which will help save crops beyond those specifically targeted by this proposal.
Specifically, Activity 1 will focus on diseases and plant pathogens identified as being highly destructive. Efficacy trials for downy and powdery mildew and Botrytis blight plant protections products will include single active ingredients and programs with tank-mixes that combine and alternate modes of action. Pythium, Rhizoctonia, and Thielaviopsis will be used to inoculate susceptible plants in individual trials. Replicated studies will include varying application rates and intervals of reduced-risk fungicides and biocontrols. Data will include plant quality, health, and size. Activity 2 will include single-spored Botrytis cinerea isolates collected from symptomatic petunia, geranium, or poinsettia growing in Michigan ornamental greenhouses. Some of these isolates have been screened for resistance to specific plant protection products including thiophanate-methyl, boscalid, fluopyram, iprodione, fenhexamid, fludioxonil, pyraclostrobin, and cyprodinil in a discriminatory dose germination-based assay. Activity 3 ensures the results and recommendations are disseminated to extension educators, growers, florists, registrants, and allied industries via presentations and publications.