This year, my courgette plants have taken a real hammering from powdery mildew. A condition that will weaken and even kill courgette plants and other squashes. After all of that hard work, I wish I had invested in a few mildew resistant strains.

What it looks like

White, icing sugar like fungus forms on the top side of each leaf. This enviably results in a poor crop as many of the young fruits rot and fall off before maturing.

Resistant courgette varieties to try

Courgette ‘Soleil’

Courgette Soleil is a superb garden variety. Plants in our trials remained healthy and were slower to succumb to mildew than any other courgette variety, thus extending the harvesting period. The bushy plants of Courgette Soleil produce a huge number of smooth, straight, delicious, yellow courgettes, adding colour to your meals. Early maturing fruits and long harvest season if cut regularly. Seeds are in the RHS Vegetable Collection.

Courgette ‘Firenze’ F1

Cucurbita pepo. Easy to grow and very prolific and cost effective for the space each plant takes up. Courgette Firenze produces high yields of small, slender courgettes throughout summer if picked regularly. Perfect for growing in a bucket sized container on a sunny patio.

Marrow ‘Tiger Cross’ F1

A remarkable new F1 hybrid marrow of the Striped Green Bush type but which is earlier, better cropping and more uniform. Marrow Tiger Cross also carries resistance to cucumber mosaic virus which can be a real crop spoiler. The attractive fruits can either be cut at 10-15cm (4-6in) as courgettes or left to mature as marrows. Marrow Tiger Cross is excellent eaten lightly cooked, freshly picked or is suitable for winter storage.

Courgette ‘Defender’ F1

A very heavy and early yielder of solid mid-green courgettes. The early yield is almost twice that of some other courgette varieties and it just keeps producing firm, remarkably heavy fruit right through the season. Courgette Defender has an open habit which lets you see and pick the fruits easily, and it has excellent resistance to Cucumber Mosaic Virus.

Courgette ‘Dundoo’ F1

Courgette Dundoo produces huge yields of glossy, dark green courgettes. Large open bush habit for easy picking.

Avoiding & treating powdery mildew organically

  • Ensure that you treat your infected plants at the very onset of infection – copper or sulphur is the convention method for treatment.
  • Wet the leaves of vulnerable plants – water can kill the young mildew spores.
  • Ensure plants have good ventilation at all times. Avoid semi-shade.
  • Avoid excessive feeding as this may increase leaf formation – more food for the mildew.
  • Spray with a mixture of 1 teaspoon of baking soda in two pints of water, with a few drops of olive oil.
  • Rotate your crop so that the same plants aren’t placed in the same spot as last year’s infection.
  • Ensure that your plot/greenhouse is free from clutter.

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