White spots on Courgette leaves in Green House

selinasally

My first time growing them - when I water I try not to get the leaves but the humidity is high in there despite the door and windows being opened …should I take the leaves off ? Can it spread to my tomatoes ?or even within the same plant ?

Dovefromabove

That looks like powdery mildew which usually appears on plants that are stressed by drought … I see that your courgettes are in growbags … although the manufacturers recommend them for such use, I find that the amount of space and compost is inadequate for them. However we are where we are, so what I would do is ensure that they are kept well watered. Courgettes need more water than tomatoes. 

There are different sorts of powdery mildew and they tend to be host specific so your tomatoes are likely to be affected by the mildew on your courgettes. 

😊 

selinasally

Dovefromabove said:

That looks like powdery mildew which usually appears on plants that are stressed by drought … I see that your courgettes are in growbags … although the manufacturers recommend them for such use, I find that the amount of space and compost is inadequate for them. However we are where we are, so what I would do is ensure that they are kept well watered. Courgettes need more water than tomatoes. 

There are different sorts of powdery mildew and they tend to be host specific so your tomatoes are likely to be affected by the mildew on your courgettes. 

😊 

Thank you this is what I thought - so they have all got these growing collars on so they get plenty of water - I water them thoroughly daily so don’t feel that it is a water issue - should I cut the leaves off ?

Kili

I think its lack of ventilation. As with most greenhouses there's no mechanical ventilation to keep the air moving and replacing with fresh . The humidity and lack of forced air movement even with doors and vents open can create this situation. My cucumbers at the moment are in the same situation. That said the plant continues to produce cucumbers so I just let it run and just remove the worst of the leaves.

There all well watered using a wicking system to ensure they only take up the water they require so its unlikely ( at least in my case that lack of water is the issues).

There's some interesting information on this page which suggests a fungicide may be used to treat the condition.

As Dove says growing courgettes in a grow bag is very limiting there hungry beasts and like to spread I would were possible grow them in the ground  outside in future. Better ventilation and no restricted root growth.

it's probably to late, but I would drag the grow bag outside and leave it there. Take off the worst affected leaves and spray with a fungicide

Good luck hope you get some courgettes.

selinasally

Thank you - I was wondering about taking them outside 

Dovefromabove

I've always grown mine outside ... the only time we had real problems with powdery mildew was when they were in a raised bed which dried out much quicker than  the ground, even with rigorous watering.  

selinasally

would it help to cut the leaves off ?

Dovefromabove

I always feel that as long as there’s some good green tissue then they’re photosynthesising and feeding the plant. If the leaves start to shrivel then I cut them off at the base of the stem.