Yellow Leaves & White Spot Leaf Problems for Courgettes and Pumpkins
Courgettes, Squash and Pumpkins have giant leaves, which unfortunately makes them vulnerable to a range of leaf diseases.
If leaf symptoms are spotted early, you might be able to save the plant.
Quick Signs to Look for:
- Yellowing leaves – round the edges or all over the leaves,
- White powdery spots – it looks like talcum powder,
- Brown or Black spots on leaves,
- Leaf stems wilting or bending over despite watering,
- Curling leaves.
Here’s some of the Leaf Diseases that I’ve had this year:
1.Yellowing Leaves
Yellowing leaves range from yellowing around the edges to covering all of the leafs surface area.
Causes of Yellowing Leaves
This is a tricky one as it could be a number of things like overwatering, but if you are watering regularly and you haven’t got any of the other leaf diseases, it is most likely to be a Nutrient deficiency.
Courgette, Pumpkin and Squashes are heavy feeders and need a constant supply of nutrients.
Adding Nutrients before Planting:
Multi-purpose Compost – You’ll need at least 2 bags of compost in the area you’ll be planting in for 1-2 pumpkin or courgette plants.
Well rotted manure or farmyard manure from the garden centre – Add this to your raised bed at least 6 weeks before planting. Manure needs to be dug into the soil and settle otherwise it could burn your plants.
Adding Nutrients whilst the Plant is Growing:
Multi-purpose Compost – Add another layer of compost to the surface of the soil and water so the nutrients get down to the plants roots.
Liquid Plant Food like Tomato Feed – Use liquid base Plant food so it gets absorbed quickly from the soil into the plant through its roots. Most liquid feed is mixed with water, check the instructions on the bottle.
After flowering, Pumpkins & courgettes need a high Potassium fertiliser for fruit formation (pumpkins or courgettes). Tomato feed or a balanced liquid feed will do the job.
Nutrient Ratio
On the back of your Liquid feed bottle, you may notice a Ratio of 3 numbers. It might look like this: 8-8-8 which is a balanced feed.
This example shows 8% Nitrogen (for green leaf growth), 8% Phosphorus (for flowers, root & stem growth) and 8% Potassium (for fruit & healthy growth).
2.Powdery Mildew
This is a common large leaf fungal disease that produces white talcum powder spots on the leaves. The fungus forms in cool, wet and humid conditions and where the leaves don’t dry out.
The fungus can jump from leaf to leaf in water splashes or even as the raindrop rolls onto another leaf so does the fungus. When the leaf is dry, the fungus can also be blown onto another leaf. Quickly the whole plant can succumb to the fungal disease.
How to get rid of the disease
- Cut a few of the leaves with the disease covering the whole of the leaf.
- Cut leaves off that open up the leaf canopy so the rain can fall on soil and not the leaves.
- Do not cut off too many leaves or the plant cannot photosynthesise and produce plant energy.
- Water at soil level not from above, to stop the disease spreading.
- A solution of 1 teaspoon of bicarbonate soda and 1 cup of water in a spray bottle to spray on leaves is supposed to stop the fungus.
Will my Pumpkins or Courgettes be affected by Powdery Mildew?
No, as long as they are growing already. as long as the vine and some leaves are still green, the plant will still be able to photosynthesise and send energy to the rest of the plant to grow.
If however your leaves are all covered in Powdery Mildew and your leaves are turning yellow to brown and dying, these are signs the plant is dying.
Leave the pumpkins on the vines until the stem at the top of the pumpkin goes brown. Then cut the stem off to store the pumpkin with the stem on for longer storage times.
My Pumpkin & Courgette Bed
Example of how quickly Yellowing leaves and Powdery Mildew diseases take hold of your plants.
Week 1 – Noticing Leaf Edges Yellow
Week 1 – beginning of August, I noticed the leaf edges have turned yellow. There are 2 pumpkin plants (& 3 pumpkins) and 2 courgette plants in this bed meaning, the nutrients might be stretched.
I topped up the compost on the soil around the plants and watered at soil level.
Powdery Mildew appeared on a few leaves, so cut off the 3 worst affected and opened up a gap to water in.
Week 2
The leaves are really suffering and some have turned more yellow than green. Powdery Mildew covers nearly the whole plant, some leaves worse than others.
The 3 pumpkins have been raised off the soil on small blocks of wood and have put on some growth from the compost addition.
This week I’m trying the spraying of 1 teaspoon of bicarbonate of soda and rest water method of spraying on the leaves to stop the fungus and cutting off severely affected powdery mildew leaves & old brown leaves in an attempt to stop the disease.
Pumpkins have not been affected and are growing well. I’m also still getting marrows off the courgette plants.
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