Plant Parenting: How To Spot The Signs Of Sickness

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Hydroponic farming containers are closed systems where plants are given all the requirements they need for life – water, nutrients, light, air and an optimal temperature. Though your plants love these conditions, unfortunately, so do many pests and pathogens. Thankfully, container growing systems offer a controlled indoor environment, so it’s very difficult for pests to get in. However, in the case of infection, it’s important to know the signs and symptoms of these diseases and pests. The best management strategy for these pests and pathogens are preventative measures. This overview will discuss how to prevent the common diseases that love the warm and humid environment your hydroponic system hosts.

Common Fungal Diseases


Powdery Mildew

Powdery mildew is a disease caused by a variety of fungi in the Erysiphales and Podosphaera family. It is characterized by a white, powder-like appearance on the surface of any above-ground plant – stems, leaves, flowers, or fruits. The first sign of powdery mildew occurs on younger leaves as they begin to curl. The upper surface of the leaves starts to display a white or gray powdery growth in spots. The powdery growth may also appear on young flower buds and they may remain unopened. As the disease progresses, aged infected leaves turn brown and drop off.


Downy mildew

Downy mildew is caused by various fungal species. The most common genera are Peronospora, Plasmopara and Bremia. Downy mildew is a foliar disease (most commonly seen on leaves) that affects many edible plants, especially leafy greens and brassicas. Firstly, white, gray, or purple spots appear on the underside of the leaf surface. Discolouration on the upper leaf surface appears, corresponding to the spots on the lower surface. The leaves begin to turn yellow or brown and drop off. A severely affected plant will have stunted growth and will eventually die.


Gray Mold

This disease is caused by the necrotrophic fungus Botrytis cinerea. It is an airborne disease that affects mainly fruiting and flowering plants but can transfer to your leafy greens, brassicas and herbs. White or gray fuzzy masses (spores) appear on the lower, older foliage. The leaves and shoots form brown lesions, and they may drop off from the plant and die. On fruits, the fungus can spread all over, resulting in a gray-blue mold coating. Flower buds may also be affected and may fail to open.


Root Rot 

Root rot may be caused by a variety of fungi – Fusarium, Phytopthora, Pythium, and Thielaviopsis. They commonly show similar symptoms such as stunting and wilting despite the fact that the plant is still given a sufficient amount of water. In all cases, the key diagnostic feature is the roots. Healthy roots are white and branched, whereas roots affected by root rot are a discoloured brown and are often stunted. Once the roots are infected, the leaves may start to turn yellow and the plant will wilt and die.



The best way to address these diseases is by implementing strong prevention strategies. Fungi love a moist environment with poor airflow, something that is common when plants are overcrowded and form a dense canopy. Therefore, ensure that your system is set up with good air circulation. This could include keeping fans running consistently and avoiding dense seeding. As well, make sure that your system has proper drainage and is at a high enough temperature to avoid condensation. Foliar surfaces should be kept dry, as the moisture invites fungi. Similarly, overwatering your media invites fungi that primarily infect the roots of crops. 

As part of your standard operating procedures (SOPs), you should be completing a checklist of weekly tasks including scouting for diseases and pests. Watch out for signs of poor airflow, high moisture, and any oddities in plant growth. Keeping your plants healthy makes them less susceptible to disease, so it is important to limit plant stress by providing them with their optimal temperature, nutrients, and water supply.  Make sure to sanitize any tools or equipment regularly. Finally, there are many disease-resistant varieties of plants available that do very well hydroponically and can be included in your next crop rotation. 

Investing in prevention strategies will allow for early detection to limit the spread of fungal diseases. However, if you are noticing signs of disease such as discolouration, wilting, or the appearance of mold, contact an expert in your area to retrieve definite fungal classification. Be sure to collect samples before carefully removing all infected plant matter from your system.

Learn more about hydroponic farming, and how you can grow food locally year-round!

Molly Neave