This morning, one of our customers asked us if we had any advice on Powdery Mildew, a fungal disease that you might have seen on the leaves (and sometimes stems and flowers) of your courgette plants. It affects lots of other plants too, like cucumbers, peas and some fruit trees/shrubs, and is easily recognisable for the white patches that start appearing on the leaves and soon spread. Here are our mildewy thoughts…
The main cause of powdery mildew is a lack of water, particularly if this is then followed by a bit of water logging. It’ll often happen when a dry spell is followed by a downpour of British Summer proportions.
How to avoid it.
Firstly, make sure your courgette plants have good drainage to prevent any water logging. Secondly, when it’s dry, make sure you give them plenty of water, regularly, and apply a mulch to prevent the soil from drying out.
The other thing to do is ensure they have enough space for the air to circulate. This is where plant spacing comes in – if they’re a little close together then you could move one to give the others more space. 1 metre between plants is a good spacing.
How to treat it.
If you already have this problem with your courgettes, or any other plant, don’t panic. As long as they’re not too badly affected then you should still get a decent crop from them.
To keep the problem at bay, you need to cut off badly affected leaves and preferably burn them (otherwise the mildew will spread). To treat the problem organically you could try mixing one part milk to nine parts water and spraying the leaves lightly on a warm, dry day. Make sure it’s done in the morning, not the evening. Leave it for a couple of weeks and then repeat. It’s not 100% effective, but it’s worth a try.