Every nursery should have a scouting program to detect and control Phytophthora species. This section describes a general scouting program specially adapted for Phytophthora diseases, but the program can also be used for many other pests and diseases.

Step 1: Setting Up a Phytophthora Scouting Program.

The first step in starting a Phytophthora scouting program is to list what plants are grown in each area of the nursery. While all plants will need to be scouted, areas where susceptible hosts are grown and where the conditions most favor the growth of Phytophthora disease are your “high-risk” areas and will need more frequent and thorough inspections. These areas might include:

  • Low areas in fields or container yards, or any place where water puddles and contacts plants. Low areas are great growing grounds for Phytophthora disease development.
  • Any place where leaf debris has collected.
  • Any areas where plants have recently been brought into the nursery from another location.
  • Areas with Rhododendron, Camellia, Kalmia, Viburnum, and Pieris which are highly susceptible to Phytophthora ramorum and other Phytophthora species.

Step 2A: Inspections in the Field

  • Scout every block of plants regularly; 10 to 12 times a year is good.
  • Visually evaluate every block as a whole. Try not to just zero in on a single, sick-looking plant. The entire block may be involved.
  • If you see a problem, increase scouting in that area to determine probable cause. This is when you CAN zero in on the sick-looking plant. Work carefully and keep records.
  • If the entire block appears normal, then select a small subsample (5 to 10 plants) for closer inspection. Randomly select plants in the middle of the block. They may all look fine, but as you have learned, the disease may be in a part of the plant that is underground or difficult to see.
  • Examine symptomatic plants as carefully as possible to determine a cause. Since it is impossible to examine the underground portions of the plant in the field, carefully examine the aboveground portions.
  • Send symptomatic samples to a laboratory for analysis.

Step 2B: Inspections in the Container Yard

  • Scout every block of plants regularly, regardless of size; 10 to 12 times a year is good. Training employees to inspect constantly might be one way to accomplish this goal.
  • Visually evaluate every block as a whole. Try not to just zero in on a single, sick-looking plant. The entire block may be involved.
  • If you see a problem, increase scouting in that area to determine probable cause. This is when you CAN zero in on the sick-looking plant. Work carefully and keep records.
  • If the entire block appears normal, then select a small subsample (5 to 10 plants) for closer inspection. Randomly select plants in the middle of the block. They may all look fine, but as you have learned, the disease may affect the roots and be difficult to inspect.
    • It may be necessary to remove the container from the block to make a really close inspection.
    • Look for leaf discoloration or leaf drop.
    • Remove the plant from the pot. Examine the roots.
    • If the roots appear healthy, return the plant to the pot and record your findings.
  • If you observe any disease symptoms such as off-color leaves, drooping or wilted leaves, or dead or dying branch tips or buds, carefully inspect the entire plant to determine the cause. You will need to remove it from the pot to examine the roots and media.
    • Excessively wet media may indicate a drainage problem which could lead to a Phytophthora problem.
    • Insect presence and feeding can indicate both insect and disease problems.
    • If you find a disease problem, refer back to the Diagnosis and Sampling part of this course.
  • Keep in mind the nursery’s pest history, environmental conditions, product line, and shipping destinations. Growing conditions and shipping requirements may mean increasing the number of inspections during a critical time of pest development or inspecting for specific symptoms such as root rot, cankers, or leaf and shoot blight.
  • Make notes about nursery operations; for example, new plant introductions, pruning, major spray applications, flooding, irrigation mishaps, and recent weather. These all may be clues to identifying a problem later.

Step 3: Inspection Reports

  • Record all inspections, dates, what was inspected, what was found, who did the inspection, and any nursery cultural notes.
  • File all reports so that they can be reviewed before the next inspection.
  • Inspections that reveal any pest or disease problems need to trigger an action plan to correct the problem.
    • If you have discovered a problem area, and no controls are available, destroying the infected nursery stock may be your only option.
    • Note cultural practices or chemical controls on the inspection report for future reference, if the disease persists.
  • Inspections that do not result in identifying pest or disease problems still need to be recorded.
  • Evaluate all action plans and scouting programs continually. Weather conditions change. Plant material will change. Cultural conditions change. With all these variables, your scouting plan and action plans to solve problems will need to change, too. If you are finding pest and disease problems when plants are on your loading dock about to be shipped, your scouting program is missing them. Alternatively, if you catch problems before they enter the nursery, then you are doing well.

Importance

You can see why it is important for every nursery to develop and maintain a scouting program. It is critical to detect diseases, such as those caused by Phytophthora ramorum, as early as possible to prevent the spread in your nursery or the inadvertent spread from your nursery. You will learn more about Phytophthora ramorum in the next chapter.