Powdery Mildew should be familiar to anyone who has perpetrated a vegetable garden for more than a few seasons. It is a powdery white / off white residue that appears on many different plants but is particularly fond of pumpkin, Squash, cucumbers and melon, curcubits. Other fruits, vegetables and herbs are also afflicted. Powdery mildew destroys a plants ability to produce chlrophyl via photosynthesis, it by blocks out sunlight. It spreads rapidly from leaf to leaf and plant to plant even amongst different species.
There are of course a multitude of chemicals available that claim to control or reduce powdery mildew, none are 100% effective, none are even 90% effective, all help curtail this menace to one degree or another. A simple and inexpensive DIY remedy that has the endorsement of many field studies is a simple foliar spray made from milk.
The initial scientific endorsement of milk as a treatment and prevention of powdery mildew was from Canadian researchers back in the 1960s. Many studies since than have replicated and added to the peer reviewed consensus that milk is an effective treatment for powdery mildew.
Effectiveness of cow's milk against zucchini squash powdery mildew (Sphaerotheca fuliginea) in greenhouse conditions
Mode of action of milk and whey in the control of grapevine powdery mildew
The effect of milk-based foliar sprays on yield components of field pumpkins with powdery mildew
There are several theories as to why milk works, but from a gardeners perspective the only thing we really care about is that it works with minimal side effects. It is hypothesized by some researchers that the proteins / lactaids in milk interact with sunlight to create an antiseptic with anti fungal properties. Powdery mildew and other fungi are scorched away fairly quickly. In order to be effective, the milk sprays should be applied durring the day in bright sunlight. Repeated weekly applications are also advisable.
You may or may not experience a foul sour milk odor for a brief period if you apply it heavily, but this has not been my experience, only a very mild short lived smell taht dissipates quickly.
To make your milk spray add whole milk and water, 70% water 30% whole milk. This dillution ratio is not written in stone, it is simply what I use, other gardeners use various formulas, but it should most definitely be dilluted. Even if you have not noticed powdery mildew, it is advisable to periodically use the milk spray as a preventative measure, particularly if you've had fungal issues in the past.
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