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Disease control

Guide to Disease Control

Pythium, phytophthora and fusarium are some of the most common diseases in hydroponics.  They can spread rapidly throughout a system and kill plants within a few days. 

The following management practices will significantly reduce the risk of disease:disease-control-in-hydroponics

1. Maintain good general system hygiene: Diseased foliage should be promptly cut from plants and removed from the growing area along with other waste material. Surfaces must also be kept clean from dust, dirt and spillages.

2. Pest management: Insects spread disease from one plant to another via sap transfer and therefore must be prevented from entering the system (Fig 1). To help achieve this, filter the air supply and minimize traffic into the growing area.

3. Maintain the cleanliness of the nutrient solution: To achieve this dose the nutrient solution with FloraMax System Maintenance. A clean nutrient solution will help avoid issues such as root browning and fungus gnat infestation.

pythium-in-hydroponics4. Humidity: Controlling humidity will prevent spore germination for many diseases. Keeping ‘relative humidity’ at 60-70% offers the best compromise for both disease prevention and plant growth.

5. Pre-treat make-up water: Untreated surface waters (e.g. dam, creek) and stored water (e.g. rain tank) should be treated prior to use. To achieve this add Pythoff directly to the water at 0.4ml/L (1/3 tsp/gal) then stir well. Store this water in the dark and do not use in the system for at least 24 hours. Disregard this treatment process for new tap waters or waters being treated with reverse osmosis filtration.

6. Use a medium with good drainage properties: Poor drainage promotes fungal diseases.

7. Minimize plant stress: Maintain correct water and air temperature, light intensity, nutrient concentration and pH. Doing this will help produce a strong, healthy plant that is best able to defend itself against disease attack.

insects-in-hydroponics8. Clean the system thoroughly between crops. This will help prevent disease problems in the next crop:

  • Step 1. Remove plants and medium from the system then do as much manual cleaning as possible.
  • Step 2. Partly fill the reservoir with water and lower its pH to between 4.5 and 6.0. Then add FloraMax System Maintenance at 25ml/L (5 tsp/Qrt) and mix well.
  • Step 3. Over a period of 24 hours, run the pump at least once every hour. Note, ‘flooding’ may be necessary to contact hidden surfaces e.g. underneath the upper surface of channels.
  • Step 4. Discard this solution then flush the whole system several times with fresh water. Where fine drippers and sprayers are used it may be necessary to individually dismantle and clean each unit.

9. Seeds and cuttings: Ensure they are from a reliable source and disease free. Be aware that looks can be deceiving. An incubation period is required for spores to germinate and become recognizable. Also, “unfavorable” conditions can cause diseases to lay dormant until conditions become favorable.

For more see page 65 of the FloraMax Hydroponics Manual.

© Andrew M Taylor

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