My research focuses on integrated disease management (IDM) for regionally important diseases that are difficult to control in ornamental plant nursery production. My approach in selecting potential control options is to first consider what biological information may be lacking about the plant pathogen to change our status quo; second to evaluate relevant sanitation, cultural and chemical controls to verify efficacy; and third to determine what combination of controls provides the best balance of control and cost. IDM is justified when no single control works well.
Ornamental plant production is a complex cropping system. The industry markets a broad diversity of horticultural plant selections and traits (environmental tolerance, flower color, plant form, etc.), often growing multiple cultivars of a single plant species. Disease tolerance is specific to each cultivar and a number of valuable cultivars have moderate disease susceptibility issues. In an IDM approach, sanitation and/or cultural management practices serve as a first line of defense to contain spread and create an environment unfavorable for disease development. Fungicides provide a second line of defense to reduce infection and/or development of inoculum. Disease control options should be flexible so producers can select based on efficacy and cost relative to the environment, disease problems and management styles of their production facility.
My five year project plan includes the following projects.
IRRIGATION WATER TREATMENTS.
Objective 1. Determine efficacy of disinfectant flow rates in irrigation water.
Approach. Chlorine dioxide dose responses to control Phytophthora nicotianae will be evaluated under various water quality treatments in the laboratory, than validated in a field scale irrigation system.
Objective 2. Determine seasonal dispersal of Phytophthora propagules in containment ponds.
Approach. In-ground tanks will collect irrigation run-off from container-grown shrubs infected with Phytophthora species. The water will be monitored for the seasonal presence of Phytophthora propagules and be used to irrigate healthy container-grown shrubs.
Objective 3. Evaluate seasonal treatment of irrigation water with disinfectants.
Approach. Seasonal treatment periods will be selected from the results in Objective 2. Seasonal and continuous water treatments will be evaluated by the severity of disease development.
INTEGRATED DISEASE MANAGEMENT IN PROPAGATION.
Objective. Evaluate preventive and reactive disease management strategies to control Pseudomonas, Colletotrichum, and Rhizoctonia in plant propagation facilities.
Approach. Initially, single control methods will be evaluated in response to problematic dispersal mechanisms relative to each pathogen. A series of experiments will follow to challenge control adding complexity by integrating preventive and/or reactive disease management strategies.
CONTROL OF LEYLAND CYPRESS BLIGHT.
Objective 1. Monitor seasonal and distance dispersal patterns of Passalora sequoiae spores.
Approach. A 24-hour continuous Buchner air spore trap will monitor aerial spore dissemination. Intermittent 10-minute rotorod spore traps will be set out at regular intervals to a maximum distance of 100 meters. Healthy plants will serve as sentinel bait plants to monitor infection and will be swapped at regular intervals for new sets of healthy plants.
Objective 2. Evaluate timing of fungicide applications and pruning periods to control Leyland Cypress blight.
Approach. Based on results in objective 1, fungicide timing strategies and pruning periods will be evaluated. Healthy and diseased plants will be placed in experiment plots and treated according to schedules. Disease development will be evaluated at regular intervals.
FUNGICIDE COVERAGE USING AIRBLAST SPRAYERS.
Objective. Identify degree of fungicide coverage needed to achieve control and optimal nozzle patterns needed to achieve sufficient coverage in ornamental container-grown shrubs.
Approach. 1) Measure disease development of Rhizoctonia web blight on container-grown azaleas that have been sprayed with a range of fungicide coverage patterns to determine the level of coverage associated with no, low, moderate, and high levels of disease development.
2) Compare flow rate arrangements of nozzle types and sizes, and tractor speeds with several types of commercial airblast sprayers to control disease across a 100 foot block of container-grown plants.