Backyard Aquaponics
A place to discuss aquaponics

My cucumber plants seems very badly. I don't know why this happened, a week ago they were very healthy. . All the other plants are fine, only cucumber has this problem.

Powdery mildew...it sucks on cubrits. I've tried milk sprays, baking soda, and Neem(rafts), but the best thing I've used is Seranade. it's an OMRI approved fungicide that is bacteria based. pricey, but seems to work the best. Once they get that bad, I've never been able to get much fruit to mature...no shade and they burn up here. Almost have to strip off all infected leaves, spray all daily for a few weeks and try and protect any new growth. No overhead watering, and lots of air movement will help also. Good luck.

Despite what many otherwise reliable gardening sources may say, Powdery Mildew thrives on leaves in dry conditions, not wet. Wetting of leaves, even without any anti-mildew sprays, does help keep it under control.
As Chris says though, the leaves in your pics are beyond saving. Best to remove then, carefully so as not to spread the mildew further.

Have to disagree with that one. Every single time we start getting our Summer rains, typically late afternoon, we have huge issues with powdery mildew, as well with other fungal pathogens. In turf, the same hold true. Last year was very wet, and grey leaf spot and Brown patch were the worst in decades. Wet leaves = fungus problems.

It is the humidity that makes it worse. I get it every year on my curcurbits especially late in summer when there is high humidity overnight


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Plants that have nutrient deficiencies can also be extra proone to mildew. A shot of potassium (bicarbonate or hydroxide (but not too much) in the system water and a foliar spray can help but as others have said most of those leaves have had it.

Last winter, which was very dry with very low humidity, with no rain for many weeks at a time, my peas in the greenhouse were covered in Powdery Mildew, and they had never had a drop of water on them since I planted them.
High humidity certainly encourages fungal growth of many types, but Powdery Mildew isn't one of them, in my experience.

After some research, it can and does occur in dry conditions as well. We just always see it during the Summer, which also is our wet time. Coincidence I guess. It did mention washing spores off, but also said that could lead to additional problems. Damned if you do....