Topic: Mottled cucumbers and courgettes

[littleweed]

My cucumber and courgette plants, about 6-8 inches, both have white and brown papery patches all over the true leaves.  They look a bit like splashes but I have watered only the soil not over the plants.  They are on the sunny windsill in the garage which adjoins the house so not centrally heated but warmer than outside.
What have I done ? Are they OK ? Help ! :(

[Mrs Ava]

And no water on the leaves......the frost couldn't have got them could it?  Very curious.  In the garage, are you sure nothing else could have splashed on them?  Sorry, not much help am I.  :-\

[derbex]

Beasties? Mildew? Mine go like this in the greenhouse -sometimes from a very obvious mould, & sometimes from spider mite. Have a good look at the leaves especially underneath. I control with soft soap spray for beasties and bicarb or milk solution for the fungii.

Jeremy.

[Gadfium]

Similar thing happened to my freshly germinated cucumber plants on a south facing windowsill. I looked up the problem in D G Hessayon's 'Vegetable & Herb Expert' and on p.56 I found a drawing which looked to give the perfect explaination... 

SUN SCALD - pale brown, papery patches sometimes occur on the margins of the leaves & shrinkage of the areas takes place; caused by exposure to bright sunlight.

Whipped the plants away from their glass-magnified roasting residence, & stuck them on a much cooler, shadier, west windowsill for a couple of weeks to recover. The papery patches gradually dried out, and I rubbed the dead bits off. An appraisal of the damage revealed that I'd managed to roast off all the seed leaves and most of their first true leaves. Needless to say, it has taken the plants a long time to pick up (I really did have them in a hot spot  :( ), but they are still alive, and were looking healthy enough to go into the greenhouse four days ago.

[tim]

Could you have answered my query?

But my patches (on potatoes in the greenhouse) have a glasslike back to them, with all the green gone.

[sweet-pea]

Tim

I think that could be due to a caterpillar/larvae.  I seem to remember reading about a pest whose larvae eat the tissue between the leaf upper and lower surfaces leaving it looking like your photo.  Can't remember what it was at the moment though.

[sweet-pea]

I've just had a quick google, and didn't find anything relating to potato, so I'm probably completely wrong!

[tim]

Thanks - it seems more like a creature than physiological. But it must be a B clever creature. I check constantly & there's nothing to be seen. Any similarity to yours, littleweed?

Here's another version. Remember that these are greenhouse plants.

[aquilegia]

I was thinking some kind of insect/larvae too. It looks like all the green tasty bits have been munched.

[sandersj89]

Could it be some sort of Leaf Miner?

Jerry

[Gadfium]

Tim - The closest thing in Hessayon's 'Potato Troubles' section, seems to be caused by a capsid bug... 'small brown spots which later turn into holes appear on the foliage. Young shoots may be distorted and the crinkling of small leaflets may be severe'. Treatment - damage usually too small to affect yield. If severe spray with permethrin/fenitrothion. Capsid bugs are about 1/4" long & greenish in colour. Their saliva is toxic to the plant, so when they suck the sap, they kill the tissue.

But... although your 'above' pic fits the bill, your underleaf picture looks more like a straight munch attack... possibly leafhoppers? Green/yellow insects 2-3mm long (1/16" - 1/8") that leap from the plant when disturbed; symptoms 'a coarse pale spotting appears on the upper leaf surface'.

 ???

[tim]

I'm sorry that I seem to have diverted attention from the courgette thread.

[cleo]

In my experience `blotches` are notorious on courgettes and yes somtimes on Cus too-never stopped them cropping well though.

Just keep an eye on them.

Stephan

[littleweed]

 :D  Thanks for all that, I think the sun scald seems most likely, the garage window sill is SW facing.  Have moved them to a spot in less direct sunlight.  Will try to take a piccy of them later if I can master it.

[the_snail]

Courgettes and cucumbers can be prone to mosaic virus which caused bloches on the leaves. The bloches in the picture you provided look to me as though they have been munched by a snail or a slug. a good tip is to look for any slime trails or if there is like a silky web at the base of the plant then you might have red spider might.