Disease control in hydroponics

Pythium, phytophthora and fusarium are some of the most common diseases found in hydroponically grown plants. They can spread rapidly throughout a system, are difficult to cure, and can kill plants within a few days.

Integrated Pest Management (IPM)

The 3 ‘ingredients’ that must be present for disease outbreak to occur are a fungal source, a suitable environment and a host. If you can eliminate one or more of these ingredients it is possible to avoid disease outbreak or prevent a disease from spreading.

The following management practices will significantly reduce the risk of disease

  1. Maintain good general hygiene.
  2. Pest management: Insects spread disease from one plant to another via sap transfer and therefore must be prevented from entering the system. To help achieve this, filter the air supply and minimize traffic into the growing area.
  3. Regularly disinfect the nutrient solution: This will help prevent disease ingress via the root zone.  For preventing diseases, the importance of points 1-3 cannot be overemphasized.
  4. 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. Disinfect make-up water: Untreated surface waters (e.g. dam, creek, lake) must be treated 24 hours prior to use. Fresh RO and scheme (tap) waters are normally sterile and therefore do not require further pre-treatment. Keep in mind that the quality of all water deteriorates over time. Therefore, stored water should be regularly disinfected and kept in the dark.
  6. Use a medium with good drainage properties: Poor drainage promotes fungal diseases.
  7. Minimize plant stress: Maintain correct water and air temperaturelight intensitynutrient concentration and pH. Doing this will help produce a strong, healthy plant that is best able to defend itself against disease attack.
  8. Clean system thoroughly between crops.
  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.
  10. Knowledge of disease type: This is critical if using chemical foliar sprays because most are useful against only one or two specific diseases. The wrong choice of spray can be costly for a large commercial operation. Therefore, consult your local grow shop for advice on the correct choice of spray.

Knowledge of the disease is also useful because the environmental conditions can then be modified accordingly to lower the rate at which the disease spreads.

Note, many diseases have similar symptoms and therefore professional diagnosis may be necessary.