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15 Post-Planting Tips to Minimize Root Diseases

It is important to ensure that the growing environment for any crop is as free of pathogens as possible. It is a good start to sanitize greenhouses or the nursery and make sure the environment does not support pathogen growth. 

Once a crop has been planted, there are additional techniques that can be used to minimize potential root disease issues. Often, root disease pathogens are present somewhere in the greenhouse or nursery, so the goal is to manage the environment and crop inputs to create an environment that is not hospitable to pathogens.

Follow these post-planting tips to minimize root diseases in your crops:

  • Do not leave breakers or hose nozzles on the floor where plant pathogens are present.  Hang them on a hook.
  • Use horizontal air flow (HAF) fans to move humid air from the plant canopy to encourage faster water use by the plant and reduce potential for overwatering.  Also, HAF fans mix pockets of colder and warmer air in the greenhouse, which creates more uniform temperatures and a more even dry-out within a crop.

Hose on floor in algae

The hose is thrown on the floor where pathogens can enter through the breaker. It is best to hang up hoses. Source: Premier Tech

minimizing root disease haf fan

A horizontal air flow fan that helps move air, reduces humidity in the plant canopy and encourages a more uniform temperature distribution throughout the greenhouse. Source: Premier Tech

  • Reduce humidity levels in the greenhouse by heating the air and venting out saturated, warm air. Again, this encourages faster water usage by the plant, thereby reducing plant stress and susceptibility to root disease pathogens.
  • Space plants to improve air flow in the plant canopy.
  • Minimize the number of hanging baskets above a crop as shading slows the dry-out of the growing medium and limits air flow to reduce humidity.
  • Reduce watering frequency when it is cloudy or raining / snowing.
  • Reduce watering frequency when days are short during the late fall through early spring.
  • Monitor the growing medium's pH, making sure it is ideal for the crop, but not for the pathogen. For example, Thielaviopsis prefers a pH above 5.5, so grow susceptible crops (calibrachoa, petunia, verbena) at or below a pH of 5.5.
  • Monitor the E.C. of the crop. High salt levels in the growing medium burn roots, serving as entry points for root rot pathogens.
  • Do not underfertilize crops as they are under stress. This will slow plant growth and they can be more susceptible to root pathogens.
  • Avoid getting dust in the greenhouse from soil or gravel driveways as they harbor pathogens.
  • Monitor the roots of susceptible crops for root diseases.
  • If a root disease is found, have it tested by a lab as the choice of fungicide will vary depending on the pathogen.
  • Discard diseased plants as soon as possible. Make sure they are removed from the greenhouse.
  • If using a fungicide treatment program, rotate modes of action to reduce the resistance of pathogens.

iron deficiency wave petunia

Petunias are showing severe iron deficiency and thus are under stress. They are susceptible hosts for root rot pathogens. Source: Premier Tech


root rot poinsettia janoski

These poinsettias were overwatered due to shortening days and one poinsettia now has a root disease. Source: Premier Tech 

If you have further questions, please contact your Premier Tech Grower Services Representative or your Regional Sales Representative:

BLOE          PEEJ              LAWL

Ed Bloodnick
Horticulture Director
US-South East

JoAnn Peery
Horticulture Specialist
US-Central, Canada-Central

Lance Lawnson
Horticulture Specialist
US-West, Canada-West


Troy Buechel
Horticulture Specialist
US-North East

Susan Parent
Horticulture Specialist
Canada-East, US-New England

Jose Chen Lopez
Horticulture Specialist
Mexico, Latin & South America

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