Pests such as fungus gnat and diseases like pythium can rapidly spread throughout a system causing severe damage, or even plant death.
The following management practices will significantly reduce the risk of pests and diseases.
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.
Fig 11.1 A magnifying glass and ‘yellow sticky traps’ are invaluable for detecting the presence of insects in hydroponics.
2. Pest Management
Insects feed off plant foliage causing leaves to turn pale and then drop. Some insects target and destroy roots (e.g. fungus gnat – Fig 11.2). They also spread diseases 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. To detect the presence of insects, use a magnifying glass to routinely inspect both sides of leaves, stems, medium and roots. “Yellow sticky traps” are also useful as a forewarning (Fig 11.1).
3. Maintain the Cleanliness of the Nutrient Solution
Fig 11.3 Root browning is a typical symptom of the root disease ‘pythium’.
4. Humidity
Controlling humidity will prevent spore germination for many diseases. Keeping ‘relative humidity’ at 50-70% offers the best compromise for both disease prevention and plant growth.
Sample of Aug 19 VegaFlora test batch with all FloraMax additives and SYSTEM MAINTENANCE. Despite being exposed to indirect sunlight for 19-months there is no sign of white, stringy muck @floramaxlab
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 PLUS directly to the water at 0.5ml/L (2ml/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 ‘fresh’ RO (reverse osmosis) waters.
6. Use a Medium with Good Drainage Properties
Poor drainage promotes fungal diseases and pest infestations.
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.
8. Clean the System Thoroughly Between Crops
Fig 11.2 Common insects found in hydroponics. Insects spread disease and destroy foliage
This will help prevent disease problems in the next crop:
Washing grow systems:
Step 1. Remove plants and non-recyclable substrate then do as much manual cleaning as possible.
Step 2. Partly fill reservoir with water then add 2-4ml/L Pythoff PLUS. Ensure pH 5 – 6 and low light levels. Run pump 1-2 times per hour over 24-hours.
Step 3. Discard this solution then flush several times with fresh water. Drippers may need to be dismantled and cleaned.
Washing floors and walls:
Spray surfaces with 25ml/L FloraMax System Maintenance. Scrub well then wait 30 minutes before rinsing clean with water.
9. Seeds and Cuttings
Ensure they are from a reliable source and disease free. Be aware that looks can be deceiving i.e. 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.
