The term mildew refers to a group of phytopathogenic fungi that causes diseases in plants. Mildew is also known as ‘powdery mildew’ and as the disease spreads, the leaves curl up, necrotize and eventually fall off. The parts of the mycelium that contain the spores of the fungus emerge through the stomata of the plant. In good light it can readily be identified by the gray or purple felt like covering on the back of the leaves.
Mildew is typically found on the upper side of the leaf, however, there are exceptions. One type of mildew that only grows on the underside of the leaf is called ‘’downy mildew’’. The leaf looks as if it has been dusted with powder.
Powdery Mildew vs Downy Mildew
|Powdery Mildew||Downy Mildew|
|Fungal spots have a circular white appearance||Fungal spots have an angular and gray appearance|
|Fungus can be anywhere on the leaf surface||Fungus is limited by leaf veins|
|Leaves yellow after fungus has been present for a while||Leaves may yellow before the presence of fungus is even evident|
Treatment & Prevention
Keep humidity low and keep your growing area clean. Use GrowSafe™ as per instructions on the label referring to preventative protocol. The best treatment against these types of fungi is prevention; once they have set in and developed, they are very difficult to eradicate. Ideally, try to prevent spores coming in from elsewhere and contaminating your plants by keeping your growing area clean. You can do this by using only clean equipment and washing your hands thoroughly before entering.