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Why you should take steps if you see a grayish powder on your plants. It’s powdery mildew

By Ashley Davis Fri, Jul 12, 2024

PHOTO: Yueke

As the growing season advances, be on the lookout for a white or grayish-white powder on your plants. This is powdery mildew, a fungus that can affect a broad spectrum of fruits, vegetables, and flowers, covering their leaves, stems, blossoms, and, in severe cases, entire plants. It's not a sight for sore eyes.

Certain plants are more prone to infection, with hydrangeas, lilacs, phlox, and peonies being the most susceptible. Other vulnerable species include azaleas, blueberries, dahlias, delphinium, cucumbers, euonymus, lilacs, rhododendrons, roses, snapdragon, spirea, squash, wisteria, and zinnias. If you grow any of these, keep a close watch for symptoms.

The silver lining is that powdery mildew typically won't kill your plants unless the infection is incredibly severe.

However, if left unattended, leaves may curl and turn yellow or brown, flowers may drop, and bloom periods may be abbreviated. The fungus can also weaken plants and stunt their growth, hindering photosynthesis and reducing their nutrient absorption capabilities.

WHAT SHOULD YOU DO?

As soon as you detect the powdery coating that characterizes the disease, remove the affected leaves and discard them in the trash. Don't leave them lying around because their spores can continue to infect neighboring plants.

If the disease has spread beyond a few leaves or you're witnessing a worsening of symptoms, apply horticultural or Neem oil as directed on the package.

Alternatively, combine 1 tablespoon of baking soda with 1/2 teaspoon of horticultural oil or liquid dish soap (not dishwasher detergent) in a gallon of water, and spray the entire plant, including the undersides of the leaves, with the solution.

While baking soda isn't a fungicide, its alkalinity hinders the germination of spores, which prefer acidic environments. As the pH balance is restored, the fungus will start to grow again, so repeated applications may be necessary. Nonetheless, be cautious not to overapply, as baking soda contains salt, and excessive salt can harm plants.

Dealing with severe infections necessitates the use of synthetic, sulfur-based, or biological fungicides.

If your plants have been affected before, proactively treating them with your chosen fungicide can help prevent another outbreak.

GENERAL PRECAUTIONS

Powdery mildew typically emerges in spring or early summer. Although it flourishes in warm, humid conditions, it can also be found in cooler climates. Simple, non-chemical strategies can significantly reduce the risk of infection wherever you garden.

• Plant resistant varieties of plants, if available.

• Ensure that plants that thrive in sunlight receive at least 6 hours of direct sunlight daily.

• Plant young plants with proper spacing in mind, considering their mature sizes, and divide overgrown plants. Overcrowding retains moisture, which promotes mold, mildew, and fungal diseases.

• Avoid overhead irrigation. Instead, direct water to the soil above the root zone.

• Prune branches and stems regularly to improve airflow and expose more plant parts to sunlight.

• Remove fallen leaves and plant debris from the garden beds when your plants become infected to prevent further spread and recurrence.


NEXT: You're damaging glass hobs without even realising - expert shares common mistake
A glass expert is warning cleaning fans to think twice before scrubbing their glass hob a certain way. The routine often puts us on autopilot. Perhaps we use any sort of surface spray lying around, before quickly pressing on with other tasks. But one leading glass expert claims you're probably doing this all wrong and, when it comes to scrubbing your hobs, you ought to be a little more careful. John Cutts, founder of , warns that using abrasive sponges, too much water, and even wiping the wrong way are among the countless rookie errors he's seen in the kitchen. "There are several common mistakes many of us are making when it comes to cleaning glass hobs and surfaces," he said. "It might seem like an obvious and quick solution to use a glass cleaner, but the harsh chemicals inside this product can actually do more harm than good to the surface. "Abrasive sponges should also be avoided, and instead, you should use a microfiber cloth to clean in gentle circular motions." Several window and glass cleaners contain ammonia, which is generally effective at breaking down tough grime and stains, but may etch into the surface of your worktop over time. Switching the heat up while this chemical is still lingering may also release corrosive ammonia gas into the air. In the worst cases, this burns your eyes, nose, throat, and respiratory tract, which can even result in lung damage or death. So, to stay on the safe side, John recommends using white vinegar as a cleaner instead. This contains acetic acid which works to break down grease and grime while banishing any tough stains. And you may be surprised to know it's useful for many other household tasks too - from killing bacteria to even banishing t-shirt stains. John claims this should be wiped in circular motions to prevent scratches and marks. And no matter what, steer clear from scraping the final bits off with a knife or adding water too. Splashing this around can cause damage to the electrical parts of the hob when used in excess. He continued: "It's [also] important to clean up any big spillages when cooking as soon as possible to prevent food substances from sticking to the glass and liquids, making a semi-permanent mark on the hob. "When cleaning the hob, use a dry microfiber cloth to wipe away any dust, grime, and crumbs first to be able to properly clean the glass."

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