You walk into the garden, wiping sweat from your forehead in the summer’s boggy heat. The peppers are dangling like hidden jewels beneath their glossy leaves. The okra is dazzling with its tropical, hollyhock-like blooms. And the tomatoes are looking fine — even though you flicked a hornworm to your chickens as a treat.
But then you get to the squash patch and pea trellis, and things aren’t so dandy. The leaves look like they got dusted with powdered sugar overnight — and this is no sweet treat. You’ve got a powdery mildew problem on your hands.
What can you do about it? Let’s talk about the proactive and preventative measures that can be taken to banish this fungal destroyer from your garden.
What Is Powdery Mildew?
Powdery mildew is a garden disease caused by a fungus — theErysiphegenus for those interested. In order to understand the disease, you need to know a bit about the fungus that causes it first. You may remember from seventh-grade life science that plants use chlorophyll to transform the sun’s energy into a usable source of food for themselves. You may also remember that fungi don’t have it so easy. Lacking chlorophyll, they need to find a plant in order to parasitize some energy for themselves.
With mushrooms, dead plants are where it’s at (to our composting delight). But with other fungi like the nemesis in this article, living plants are on the menu, and it’s not to their benefit. When wind-borne fungal spores land on a nice, green leaf — from your zucchini, for example — they hang out there until conditions are right.
Then, they germinate into action, tunneling straight into the leaf so their root’s haustoriacan feed straight from the living plant. The white stuff you see on the leaf surface is the fruiting body that becomes apparent after several days of feeding.
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它几乎影响到每一种园林植物,尤其是来自芥菜、豌豆和葫芦科的植物。你可以很容易地通过白色或灰色的粉状斑点来识别它,这就是它的名字。它们从底部开始很小,最后覆盖整个叶子。
Though it does move slowly, if left unchecked, it will cause affected leaves to turn yellow and brown, and eventually shrivel. Remember, the leaf is basically being sucked dry. It can also attack developing fruit (cucumbers and pea pods are common targets) causing them to develop prematurely and have subpar flavor and texture since their tasty sugars never developed.
Sounds pretty dire, I know — but hang on. There is good news. Fungal diseases aren’t like bacterial or viral infections. In those cases, affected plants need to be uprooted and destroyed to halt the damage. With mildew problems, however, the plants in question can still give you a harvest with some careful management.
How Powdery Mildew Gets In The Garden
As a fungal infection, powdery mildew is spread by airborne spores. That basically means it doesn’t get into your garden. It’s already there, waiting for the right circumstances on the ideal plants — including your roses or lilacs.
A powdery mildew outbreak is really the result of a perfect combination of conditions. They are so specific, you can probably prepare in advance for it to emerge. As the summer passes its midpoint in your area and begins to cool off, watch for several conditions.
- Daytime temperatures with a high of 65-85 degrees Fahrenheit
- Daytime humidity between 45% and 75% (though it can be present at as low as 20%)
- Night temperatures at around 60 degrees Fahrenheit
- Night humidity around 90%
Check all those boxes, and you can almost guarantee that you will find powdery mildew somewhere in a susceptible garden. Fighting powdery mildew is basically keeping the situation in your garden from reaching the conditions it loves.
How To Get Rid Of Powdery Mildew
If you have a powdery mildew attack, you undoubtedly want it gone, but the reality is that you won’t get powdery mildew out of your garden. Even gardeners in northern areas not known for the disease can be affected by the spores when they are blown from the south on warm summer winds.
Fortunately, even though you can’t beat the unseen spread of the spores, you CAN tilt the scale in your favor by messing up powdery mildew’s favored conditions.
The passive way is to hope that temperatures peak over 85 degrees Fahrenheit again. The disease will halt in its tracks. On the other end of that spectrum, powdery mildew can’t germinate at temperatures lower than 30 degrees Fahrenheit — but by that point, your garden is certainly done growing for the year.
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假设你是一个园艺战士,不愿意让白色绒毛毫无反抗地杀死你的黄瓜和花园夹竹桃。这里有一些你可以做的想法。
Remove The Affected Leaves
除去长满霉菌的叶子。当然,你并不想让这株可怜的植物完全脱落,但去除叶子可以帮助阻止它的蔓延。此外,对整个花园进行一些仔细的修剪可能会带来更好的气流——喜欢潮湿的霉菌不喜欢气流。
Consider Sulfur, But Be Wary
You’ll see quite a bit of garden literature advocating the use ofsulfurin powdery mildew combat, but I always feel wary about spraying food plants with something that can be toxic to inhale or ingest. Additionally, sulfur is not a cure-all for plants. There are some it can actually harm such as apple trees or grapes.
As always when using garden chemicals, read the label carefully, and use them with discernment. If you’re protecting ornamentals like roses or phlox, I can understand, but surely there’s something a little safer to put on your future dinner!
Apply Neem Oil
Thankfully, there is a more natural, organic combatant to fungal outbreaks. Neem oil — an extract from a tree native to India — has been used as both pesticide and fungicide, and it can be used up to the day before harvest. Check outthis recipe for a homemade organic spray这可以帮助你阻止白粉病的传播。
Finally, as you wage fungal warfare, you can take steps to make your garden positively unhospitable. Enter my next points.
How to Prevent Powdery Mildew In Your Garden
在花园里,疾病是很难对付的。你不能让一株植物吃一片阿司匹林,然后把它的脚抬起来,直到它感觉好些。对抗白粉病的最后一步是拿走最初允许白粉病进入的欢迎垫。良好的园艺实践将使你的花园保持健康和强壮。足够强大,疾病将很难找到立足之地。
Consider Your Garden Location
Make sure your garden is in a good location with full sun and good air circulation. A low-lying area in the garden can create a little pocket of moist, damp air and that spells trouble.
Always Do A Fall Cleanup
In the fall,clean up your garden and remove all dead-plant debris. The spores chill out in fallen material through the winter, send them packing to a fall fire or a hot compost pile.
Work To Build Healthy Soil
Take the time to build healthy soil through constant additions of organic matter and green manures. Rich soil makes for strong plants that can resist diseases.
Choose Varieties Suited For Your Climate
Plant the varieties best suited to your specific climate. Growing heirlooms and thensaving seedsfrom the plants you grew in the previous year will help you start developing your own landrace.
This means that successive generations of plants will adapt over time and be naturally better at resisting the specific challenges that your climate offers.
Keep Plant Leaves Dry
尽可能避免湿润植物叶子。下班回家后给花园喷洒农药似乎是个好主意,但傍晚时分在豆子上喷洒农药意味着它们在日落前没有时间晾干。在凉爽的夜晚,叶子上覆盖着额外的水分,真菌就会在叶子上逗留并占据主导地位。
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当你需要给花园浇水时,最好在早上浇水,让阳光蒸发掉多余的水分。此外,尽量只给土壤浇水,而不是整株植物。滴灌软管是一个很好的工具,当你需要潮湿的根系,而不是浇到树叶。
尽量不要在潮湿的花园里工作。你可能不认为自己是疾病的传播媒介,但你的衣服和工具可以很方便地运输在水中搭便车的真菌孢子。
希望这些建议能帮助你度过下一个生长季节。如果你有任何额外的策略来赢得白粉病的胜利,把它们写在下面的评论中,我们可以从你的经验中学习。
Vivisays
如果你手边没有印楝油,除了受影响最严重的叶子不能去除,因为这样你的南瓜就没有叶子了,那么在受影响较小的叶子上喷洒牛奶(或者更好的是,无糖酸奶或类似的用大量水稀释的发酵乳制品)可以作为临时的补救措施。它不能完全治愈霉菌,但它有助于遏制它的蔓延,直到你找到一些更有效的抗真菌治疗方法,或者也许直到你在季末收获最后一个南瓜。(对我来说,霉斑总是在8月中下旬从西葫芦开始,这个时候植物的存活时间不会超过3到4周。不幸的是,在秋天晚些时候,霉菌会转移到西兰花和瑞士甜菜上,所以在南瓜上的霉菌释放孢子之前,努力控制它的传播仍然是值得的。)
The reason this works is the same as how your body (or that of your better half) keeps its constantly moist mucous membranes from developing a yeast / candida infection: microscopic fungii just don’t grow well in an acidic environment, so the body keeps a population of symbiotic bacteria around that produce lactic acid (a very mild organic acid, milder than vinegar). Only if you neutralize that acidic environment (e.g. by washing your nether bits with simple alkaline hand soap, instead of a pH neutral soap-substitute) can fungal microorganisms survive well enough to multiply and irritate the skin. The bacteria that naturally grow in milk (even sterilized milk will quickly get re-infected, if you spray it on an open surface like a leaf) also ferment the lactose sugars in the milk to lactic acid. This process eventually ends up with so much acidity that the proteins in the milk start to curdle, which is how yoghurt is made. (Cottage cheese, Mozzarella and similar white, semi-solid “fresh cheese” products are made differently, with an enzyme used to curdle the proteins instead of acid, so those wouldn’t work as a treatment against fungal diseases.)
Wren Everettsays
多么棒的小费,Vivi!我以前没有听说过这个——我喜欢你对它为什么有效的额外解释。对于我们这些不能立即获得像尼姆这样的外来产品的人来说——但我们有自己的奶动物——知道这个是很美妙的。2022欧洲杯葡萄牙vs德国我敢打赌,对于那些被他们的奶牛过度祝福的人来说,牛奶/生牛奶也会很好,哈哈。我非常感谢你的评论,希望你有一个美好的园艺季节!
Ray Whitesays
Wren,
What an excellent article. I would like your permission to share it with the readers of my Dying Time Newsletter–which is about Preparedness and frequently features gardening articles. If I am allowed to use your article I will provide full attribution to you.
I’m one of those gardeners who was told to use sulfur to fight powdery mildew and didn’t know Neem Oil could be used as well, so thank you for that information. I use Neem Oil on my fruit trees so always have it on hand. Vivi’s tip about using milk or yogurt was also news to me–and it shouldn’t have been because I recall my grandmother spraying diluted milk from her Jersey milk cow on her peas. I was a little kid at the time and never thought to ask her why she was doing that.
Please check me out on my author page athttp://www.RaymondDeanWhite.comand click on the Prepper Information button to see my archived newsletters. I hope to hear back from you soon.
Wren Everettsays
Thanks so much for the comment and nice words, Ray! We would be happy for you to share the article, especially since you’re thoughtfully remembering to provide attribution. Here’s Insteading’s requests for reposting content://m.emmstar.com/copyright/. And would you be able to follow up with a link to the newsletter, if possible? I’d like to see it!
Finally, that’s a neat memory to be able to bank on–so many Grandmas had so much knowledge that’s on the cusp of being forgotten! Thanks for helping keep it alive.
jacksays
Thanks