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Courgette Problems & Allium Leaf Miner

A couple of readers wrote in about problems with their courgettes and another has lost his entire onion crop to allium leaf miner. That’s a problem that’s getting worse as time goes on.

Powdery Mildew on Courgettes

Powdery Mildew Cucumber

Powdery Mildew on Cucumber which also affects courgettes. Affected leaves left, new unaffected leaves to the right.

Spencer writes:

I have been growing courgettes in pots for the last few years with success but the leaves usually finish up with a white powdery dust on them. Is this a fungus and how can I stop it?

It sounds like powdery mildew which is very common on courgettes and can affect cucumbers and squashes too. There’s a diary post on this here: Cucumber Powdery Mildew,  and an article on a different control method here: Biological Control for Powdery Mildew

Finally,  I cover it in my book Vegetable Growing Month by Month

Hope that helps

Poor Courgette Seed Germination

Michael Ellis writes:

I have trouble germinating courgette seeds as they rarely germinate, so I buy a few plants from the local garden centre. Have you any tips about my courgette shortage i.e. lack of germination.

Usually I’ve had near 100% germination rates starting courgettes off in 3 inch pots of ordinary multi-purpose compost but this year only 50%. Then again, I only sowed 4 seeds so not a statistically relevant sample.

A couple of tips that may help solve your courgette germination problem.

First, sow the seeds on edge. The theory is that it stops water lying on the seed and causing rot. I’m not sure if it makes any great difference but it does no harm at worse.

More importantly for germinating courgette seeds is the temperature. The optimum temperature range for germinating courgettes is between 20ºC and 35ºC That’s the compost temperature, not the air temperature. See Best Temperatures for Seed Germination

If you’ve a thermostatically controlled propagator then set it around 25ºC – if not, start them off in the house. Once they show above the soil, remove from the heat. If you’ve got a greenhouse or cold frame keep in there until they’re a few inches tall and then harden off before planting out.

Allium Leaf Miner

Hi John, for the second year running I’ve lost my entire onion crop to Allium Leaf Miner. Is there anything you can suggest that will prevent this from happening again in the future? Any help or ideas would be much appreciated.
Regards Gareth Owen.

Allium Leaf Minor Tracks Leeks

Allium Leaf Minor Tracks in Leeks. The pest also affects onions, garlic etc.

Allium leaf miner is most often a problem with leeks but it can affect any of the onion family. I wrote a full article on the problem that should help you here: Allium Leaf Miner

Posted in Allotment Garden Diary
One comment on “Courgette Problems & Allium Leaf Miner
  1. Lew Blythin says:

    as for the Allium Leaf Miner the main problem we found down our allotment was plot holders leaving leaks in the ground through to late spring as the grub can overwinter in them so when everybody put onion sets in the grub just hatched and found another home best to dig up all your over winter leaks before planting your onion set/plants and some organic farmers around this area use seline solution as a preventative it’s a bit pricey but i use Epson salts
    seems to work also giving your onions a good feed

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