Please help!! New farmer. What is this disease growing on my crops?


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My family began farming Asian vegetables just this year, so were fairly new to plant diseases and infections. The vegetable of concern is Tong choy, (ong choy). They are grown in greenhouses, and the disease is beginning to spread to other greenhouses nearby. This is very concerning for me as i have had to destroy the previous crop because of this bacterial infection. I don't want this crop to have the same disease again!! What kind of treatments can I do to help prevent/cure this infection? I've done hours of research and tried multiple fungicides with no effect. I think it might be downy mildew , but the spots underneath do not look like flour , they are spotted underneath the leaves. We have switched irrigation to early mornings and increased ventilation by opening greenhouse windows and doors.

Any help is greatly appreciated as I am out of ideas!
 

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zigs

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Welcome to the forums :)

Any chance of a macro pic? Looks more like insect eggs from what I can make out.
 
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Thank you! The last picture is a close up on what they look like, I will try to attach more pictures in a few minutes though. The specs have an appearance that looks like salt. They are not insect eggs, they attach onto the leaves and cannot be scraped off. It definately does look like some sort of fungal or bacterial infection.
 
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Looks like aphids to me too but a macro pic would be a big help
 
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Definately not aphids, they aren't bugs. Looks a lot like it though, but when I try to remove the specs they don't come off at all. These grey-white dots cover the under leaves of this plant.
 
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Definately not aphids, they aren't bugs. Looks a lot like it though, but when I try to remove the specs they don't come off at all. These grey-white dots cover the under leaves of this plant.
Then if not aphids, which do attach themselves to plants, it is hard scale insects. You cannot remove hard scale. And a disease does not normally make tiny holes in the leaves. Spray them with neem oil once every 5-7 days for 3 weeks. They will still be stuck to the leaves but they will be dead.
 
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Hmm...that might be a real possibility. I will definately look more into scale bugs. There are no holes in the leaves though, the surface of the leaf shows micro yellow spots: the under showing what is pictured above. In the past, i have tried to scrape this off the leaf to see if they were removable, but they weren't. The leaves ripped as a result of my attempt to scrape whatever this is, off. I will attach a macro picture soon to maybe help narrow down what this might be. Is it possible that this is downy mildew ? Or is it more likely to be scale parasites ?
 
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Hmm...that might be a real possibility. I will definately look more into scale bugs. There are no holes in the leaves though, the surface of the leaf shows micro yellow spots: the under showing what is pictured above. In the past, i have tried to scrape this off the leaf to see if they were removable, but they weren't. The leaves ripped as a result of my attempt to scrape whatever this is, off. I will attach a macro picture soon to maybe help narrow down what this might be. Is it possible that this is downy mildew ? Or is it more likely to be scale parasites ?
It isn't mildew, downy or sooty. It's insects thankfully. They are much easier to deal with than mildew.
 
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I found this picture on Google of downy mildew, it looks a lot like it. Any thoughts ? The conditions for it to thrive also match my conditions as well, that's why I'm starting to believe it is downy mildew.
 
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I found this picture on Google of downy mildew, it looks a lot like it. Any thoughts ? The conditions for it to thrive also match my conditions as well, that's why I'm starting to believe it is downy mildew.
IT IS NOT MILDEW, either powdery or downy. IT IS INSECTS, PROBABLY HARD SCALE. Spray with neem and you will see. Take some macro shots
 
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