Now here’s something you might be able to use in your propagation area when you start taking shrub cuttings this season.
DLV Plant in Wageningen, Netherlands has done some commercial sized research using UV lights on plant cuttings. A UV light is simply a “black light”.
They exposed plants three times a week to 75 watt UV light bulbs and evaluated the crop at the end of the propagation cycle for powdery mildew.
The treated plants had significantly less PM than the chemical sprayed or untreated plants.
But here’s the thing – you have to start the light treatment before the problem becomes apparent as it doesn’t stop PM, it mostly prevents it.
How to Do This At Home
Get a UV light bulb. You’ll find them at specialty stores or online – sometimes sold for the treatment of seasonal affective disorder (not enough sunlight during the winter causing different amounts of depression). So check specialty health stores. You may also find them at party stores or specialty lighting shops.
The light has to hit the spores before they germinate so do not crowd your cuttings at all – the light has to reach the bottom leaves.
Three times a week, expose all leaf surfaces to the light. This is likely as simple as moving the tray of cuttings at angles under the stationery light (multiple passes at different angles) rather than trying to move the light.
That takes care of the powdery mildew with no sprays or problems.
Bottom line
The first line of defense is obviously to space the cuttings out so leaves don’t touch and not to have your humidity too high (good air circulation)
But if you’ve had a problem with powdery mildew – this is a good starting point so you don’t have to use chemicals.
I do not know if it works on other fungal problems but …..
