Powdery white mildew

[Lazylightningny]

I have a constant battle with this stuff at my house, especially in one corner of the yard where a big wild cherry is. It usually comes on strong in August, and by this time of year, leaves are getting whitish and crispy. I can alleviate it somewhat by moving the affected plants away from the big cherry tree and into a more open area of the yard, also by not getting leaves wet, not watering at night, not this and not that. Too many nots. To be honest, I'm a little lazy with the fungicides. I use them as needed, but I rarely remember to spray prophylactically. It affects my prunus and malus, and my acer sacchs and japs. It has NOT, for some wonderful reason, affected my trident, for which I am very happy. So I think going forward, for my sanity, I'll just avoid the species that are affected and stick with tridents and any other prunus and malus I can find that are resistant.

 

[0soyoung]

I have some plants that get this late in the season, most notably some deciduous azaleas.But I have a new volunteer maple that has it now, I have cherry trees, and a larger variety of maples (among lots of other species) but downy mildew has never shown up on any other them (in the landscape or in pots). Regardless, I don't worry about it because the leaves will be dropping before much longer and (in close to a decade) I've not seen any lasting ill effects.

Out of curiosity, I have tried my favorite peroxide solution antifungal and it didn't seem to phase it. So, if it is really damaging your trees, you will need to exercise a nuclear option (hazardous chemicals). Maybe using a systemic (if they are legal in NY) would be a good idea.

 

[GGB]

Bummer, I've never had issues with my trees at any apartment and now that I finally own a home I'm getting barraged. I may be doing the same thing. Avoiding the trouble trees to spare nasty chemicals and constant fighting.
Thank God my pines are happy

 

[defra]

I know some people in the netherlands spray the affected leaves with milk to kill the milldew they say it works i never tried it myself tough

 

[twisted trees]

There was a bad mildew problem here due to rain almost every day from spring through summer. Neem oil solved the problem but needed to be applied often.

 

[petegreg]

I've got many species put side by side, but only E. oak and A. monspessulanum get affected by this disease. Copper fungicides work well or I've been using a product called RockEffect (sth. similar to neem oil?) recently and it works well too.

 

[Lazylightningny]

. So, if it is really damaging your trees, you will need to exercise a nuclear option (hazardous chemicals). Maybe using a systemic (if they are legal in NY) would be a good idea.

Sadly, systemics are not legal here.

I haven't found anything that actually kills existing powdery mildew. Environmental controls, pruning affected areas, and diligent spraying help to a large degree, but I'm a fail at the diligent spraying. I usually forget until it's too late. Daconil seems a pretty decent antifungal, if sprayed prophylactically. One time I went as far as spraying with daconil and using a toothbrush on each leaf, but I don't see myself doing that very often. It seems easier to just not grow the species that are most affected.

 

[Paradox]

This year has been bad for fungus issues.

Too much rain, too frequent rain, too humid.

 

[Maros]

I've got many species put side by side, but only E. oak and A. monspessulanum get affected by this disease. Copper fungicides work well or I've been using a product called RockEffect (sth. similar to neem oil?) recently and it works well too.

I use Rockeffect as well and it works partly. Product is based on pangam oil. If you start to use it in spring and use it regularly throughout the season results are rather good.

 

[Nybonsai12]

This year has been bad for fungus issues.

Too much rain, too frequent rain, too humid.

Agreed... My J. Maples have taken a beating. I think its leaf curl. I use a bayer granular at the start of the season but it didn't help prevent the problem, so i started to spray alternating a bayer spray and daconil. I was too late to help this season, growth stopped in it's tracks, leaves curled and any new growth was very small and misformed. Very disappointing year for sure on a few trees.

It's so bad I've even noticed the lower branches of a VERY large oak in the yard exhibiting leaf curl symptoms. Right above my freaking grow bed.

 

[Paradox]

Agreed... My J. Maples have taken a beating. I think its leaf curl. I use a bayer granular at the start of the season but it didn't help prevent the problem, so i started to spray alternating a bayer spray and daconil. I was too late to help this season, growth stopped in it's tracks, leaves curled and any new growth was very small and misformed. Very disappointing year for sure on a few trees.

It's so bad I've even noticed the lower branches of a VERY large oak in the yard exhibiting leaf curl symptoms. Right above my freaking grow bed.

I've seen quite a number of oaks while driving around that are showing a lot of leaf curl/fungus issues.

 

[clive bennett]

I tried the milk just make all the plants smell terrible, have you tried pruning the cherry tree, and allow more light and air around your bonsai?

 

[Lazylightningny]

My Japanese maples have dropped the leaves at the ends of the branches, but so far, the buds look healthy, so I am hopeful. I just really need to be more diligent with spraying.

Does anyone give the soil a good watering after spraying to flush any chemicals through?

 

[Nybonsai12]

My Japanese maples have dropped the leaves at the ends of the branches, but so far, the buds look healthy, so I am hopeful. I just really need to be more diligent with spraying.

Does anyone give the soil a good watering after spraying to flush any chemicals through?

Cover the soil when you spray. You don't want copper getting in the soil. I believe the same goes for daconil.