|" I have this white stuff on the leaves of my plant..."|
24 May, 2016
June Gloom Brings On Powdery Mildew...
Oftentimes we refer to June Gloom – it's part and parcel of our climate. This year we've had the May Malaise and the April Anguish. Will June forego its gloom and set us free?
Somehow, I doubt it.
June Gloom is a phenomenon of our climate. Historically, June is an overcast month with little breeze. It is hot enough, and lacks sufficient air movement and hard direct sunlight, to foster the growth of fungi on the leaves of your plant. And once given the chance, the fungi doesn't stop at just making them ugly; it kills them.
The problem is not just the lack of sunlight from the morning cloud cover. Powdery mildew, which is a common name for many different kinds of fungi (each plant species has at least one fungi which are called “powdery mildew” - some lucky plants have more than one!) does not need moisture to live but does survive in heat – of which we have plenty. We have exacerbated this problem by walling our gardens off from neighbors with walls allowing the air in our gardens to remain stagnant. The price we pay to gain a little privacy in our crushing metropolis.
When someone says, “I have this white stuff on the leaves of my plant...” It's probably powdery mildew. The first thing I do is think of the recent weather and the second thing I do is ask, “Is your garden enclosed by a wall?” Not always, but more often than not, the answer is yes. Some folks just live in an air pocket that fosters the mildew – others may have trees shading the plant in the sunniest part of the day - but all of us are faced with it. All the squashes, melons, cucumbers and even other plants can get powdery mildew.
My grandfather used sulfur to combat most fungi. It's simple and it's not very toxic. However, sulfur and squash family members (including, melons, cucumbers, zucchini – all those big leaved climbers) are stressed by sulfur and most authorities discourage sulfur on those plants.
Once your plants have it, cut severely affected leaves from the plant. If is is so bad you are removing too much of the plant to produce a crop, toss the whole plant. If you have it now, you have time to even buy fresh seeds and start over. This is what I do – except for winter (hard rind) squashes. Those I take away the most offending leaves only and leave the rest and try to nurse the plant along till the squash is ripened. I've almost always been successful.
The first action you might try is to wash it off with a hard stream of water - I know it seems counter-intuitive, but if you can wash the spores off the leaves, you may well forestall a more devastating infestation.
Some folks have reported good control using 10% milk in water (1 cup milk; 9 cups water, for example – any amount milk with 9 times of the same amount of water) sprayed to cover.
Cornmeal has been effective as well. 1 cup of cornmeal in a muslin bag, left 24 hours in a gallon of water can be sprayed or splashed over affected plants. If you choose to spray something, do it as soon as you can. Every day the powdery mildew stays, it becomes harder to avoid damage.
There are those who used baking soda, but I don't like these kitchen recipes as they are NOT benign in the soil. They can change the soil and kill the critters in the soil, so I leave them be. (The concept of using vinegar in the garden appalls me as it is very harmful to soil critters!)
If you cut off infected leaves, do not try to compost them. Your compost will not probably kill the fungus and you'll only reinfect future gardens with i
NO fungus is worth poisoning your plants or the critters in the ground. We will all survive even if the squash looks like hell. It's OK. I've looked like hell some days and no one dumped me with sulfur or worse.