Disastrous Diseases - Leaf Diseases (Part Two)
Leading on from our introduction to diseases we take a closer look at three common leaf diseases and how you can identify them in your hydroponic growing environment.
The most common plant diseases you'll find in your greenhouse will be moulds and mildews - there is no better home for these fungi to thrive in.
1. Powdery mildew
Powdery mildew appears on the front of the leaf surface and resembles a fine white coating; these are actually thousands of tiny spores. Powdery mildew comes from a family of diseases that include podosphaera, microsphaera, erysiphe, sphaerotheca and leveillula - all are a form of fungi.
It's actually quite easy to control an outbreak if you notice it early enough, but it's a disease you need to monitor regularly, especially in indoor gardens and hydroponic gardens. You may not lose your crop to a powdery mildew infection but it can heavily affect your plant yield outcome. Some research indicates a thirty precent reduction in yield from a heavy infection.
You can expect leaf spotting, bud abnormalities, discoloration, stunted growth, reduction of foliage and upturned leaves.
If you increase the air movement in your greenhouse you can hold a level of control over powdery mildew outbreaks. Another tip is not packing your plants into your hydroponic channels like they pack sardines into a can. Otherwise you restrict the air movement between the plants and their leaves. Remember - mildews love a humid environment.
Botrytis or grey mould as it's commonly known, has a greyish brown appearance on your plants leaves and looks quite furry. Infection can spread rapidly if not dealt with quickly and once grey mould gets out of hand you can have trouble getting it under control.
Tomato crops are particularly susceptible to grey mould when cultivated indoors.
Grey mould spores appear in humid environments and are spread from leaves and petal’s to a plants fruit, eventually covering the entire plant if left to its natural course of action.
Characteristic symptoms are greyish brown spores in a consistent covering (as opposed to the spotting of powdery mildew), rings around fruit (known as ghost or halo rings) and wilting above the infected area.
To avoid botrytis in your indoor hydroponic garden make sure you keep the area free from cuttings and dropped leaves, the fungus can be spread by the old, infected cuttings touching any part of a remaining plant.
Infection in new plant stock generally comes from spores travelling on the wind or spores spread through air circulation in your hydroponic greenhouse. Make sure you remove any dead plants from the hydroponic grow room before you begin any new pruning. And check new plants when you are buying them, make sure they look healthy all over.
Again sufficient ventilation is a must to keep grey mould at bay. If you do opt for a spray make sure you spray the entire plant including the underside of the leaves.
There are two schools of thought on Botrytis - some recommend trying to gently wash the leaves while scraping off the mould and then others recommend removing the infected plant all together to avoid spreading the disease through your hydroponic equipment and crop – at the very least cut away the infected area of the plant.
Either way, you should boost your plants immunity by dosing it with a product like Nutrifield Herbal Boost or Defence System - You need to build your crops immunity so it can resist re-infection. Your plant has suffered stress through these diseases and will need a boost to encourage vigorous health and abundant growth - plus it doesn't hurt to safe guard increased yield potential. A healthy plant is a happy plant after all.
3. Alternaria leaf spot
Alternaria leaf spot is known as a major plant pathogen, you might also hear this fungus called early blight or target spot.
It appears on your plants leaves in varying shades of brown. Light brown to tan to dark brown with a distinct spot in the middle that can resemble something of a bullseye. These brown spots are known as necrosis.
It can cause the leaf tissue around the infected area to turn a light green to yellow colour and in severe cases cause defoliation of the outer leaves. The discolouration occurs because the pathogen kills off the surrounding leaf tissue.
The best cure is always prevention and planning from the seedling stage is your best bet. Incorporate a defence system into your hydroponic schedule that will build resistance to disease and infection and make sure if you are working from cuttings, that the mother plant is free from disease before planting. And remember to keep your hydroponic equipment and greenhouse clean.
If you do find indictors of alternaria leaf spot, trim the infected leaves and dispose of them carefully. This fungus can make its way into your hydroponic garden via infected seeds, debris in soil outside and even from weeds unexpectedly brought in on the bottom of shoes or from a slack nursery assistant.
Interestingly enough, it can also cause common allergens in people and be the culprit of hay fever or hypersensitivity which can both lead to asthma.
Get to know the plants you are cultivating, know exactly what a healthy species looks like, and then when problems show themselves you can identify and treat them quickly. Those first tiny little spots or spores are when you want the problem brought to your attention.
Find books and reliable photographs of the plant species you are cultivating. Or if you know someone who has a disease outbreak, see if you can have a look first hand, it could help you identify your own plant diseases in the future.