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)
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
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.
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.
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.
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 pretreatment. 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 temperature,
nutrient concentration and
pH. Doing this will help produce a strong,
healthy plant that is best able to defend itself against disease attack.
Clean system thoroughly
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
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.