As the name of this fungus suggests, it is a downy mildew that affects almost all vegetables. It occurs on the surface of the fruit or leaves, and is formed by the fibres of a microscopic fungus. Where else can grey mould cause damage?
On vegetables
It forms grey-green and watery patches, or white to yellow rings, on the surface of vegetables. Over time, these areas develop a grey “skin.” Lettuce, for example, develops a grey coating and the head begins to rot. The danger of grey mould is that it can infect not only cucumbers and fruiting vegetables, but also cruciferous vegetables (e.g. broccoli, cauliflower, cabbage). It is transmitted through the air, but it can also survive on plant debris or weeds, from which it can reappear on vegetables the following year. It can be prevented by sufficient spacing, regular pruning and disposal of infested pieces.
On fruit
In fruit, grey mould is primarily found on strawberry, where it appears exclusively on the fruit. On these, it forms lighter or brown spots that gradually spread and darken. They then develop the typical grey “skin”. The disease affects ripe and maturing fruit and can destroy more than half the crop. As with vegetables, it is advisable to keep the fruit more widely spaced and not too dense. For strawberries, understocking and frequent weed control is recommended.
What about houseplants?
In the same way as on fruit and vegetables, grey mould appears on houseplants. It thrives best in a moist environment, i.e. in pots. The species does not mind the cold either, so flowers in corridors, for example, are a common target. Therefore, the best place to grow them is where there is sufficient air flow. A reasonable temperature is also important. Although these spaces will control grey mould, such conditions are suitable for other pests such as aphids. So if you find signs of grey mould in your pot, reduce the watering rate and move the flower to a warmer location.