This is neither normal or good. Infected plants develop a distinct white powdery film that covers their leaves. White blotches on zucchini leaves may be normal or may be fungus Question: My zucchini plants are large, but now they have large white spots on their leaves and stems. About a week ago the 'oldest' courgette leaves on some of my plants turned completely yellow. Hi, Some of the older, early leaves on my courgettes are turning yellow. The newer leaves look fine and there are courgettes forming, and the plant is growing. This is because they need a lot of pollination and generally, when the weather is cool, there are less pollinators about. Started by yorkiegal on Grow Your Own. Organic gardener Sally Smith answers your questions about what to do if you have mildew on your courgette leaves and how preparation is key to … B.G. The one crispy leaf on my courgettes is now turning into 2 crispy leaves, the first two leaves stay fine but it's the susequent ones that are going to Crispville. Cold weather: courgettes don't like it and will produce fewer fruits. 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. May 2019 in Fruit & veg. 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. 15 Replies 4701 Views July 01, 2012, 14:37 by Springlands white splodges on courgette leaves Started by flora on Grow Your Own. Alamogordo. What is this and should I be worried? The courgettes are a yellow variety that I have not grown before so I thought maybe it was normal Now however the leaves have developed brown patches that are joining up and the leaves are curling in at the edges which are also brown. This is nothing to worry about and the plant is healthy, it is part of the courgette leaf's appearance. Rob45 Posts: 14. Courgette leaves turning yellow. Do they need fed even though they're not flowering yet and are only at the four leaf stage? It looks like they have grains of white sand on the top surface, but there is much more on the lower surface of many of the leaves. Commonly found on a large range of plants, and is very common on pumpkins, cucumbers, courgettes, and dahlias – particularly towards the end of their growing season in autumn. They’re growing in standard bag-type multi purpose compost. I leave the greenhouse door and vent open during the day. The pot's big enough and I'm not overwatering. 7 Replies 12017 Views June 14, 2008, 10:06 by flora : white spots on courgette leaves As a Courgette plant matures the leaves often get white markings on them as in the image left. My courgette leaves are white.