White powder on plants

It can be pretty heartbreaking when your plants look less than stellar. Sometimes an easy remedy to restore plant health is adding more water or moving to a sunnier spot. If that doesn’t work and you’ve tried many options, it could be a sign of a larger problem. Your plant could have a disease.

To help you quickly diagnose and keep your plants looking fresh, we’ve compiled a handy guide below of most common plant diseases you can encounter. So the next time you see a weird substance forming on the soil or strange discoloration of leaves, you’ll be an expert.

What About Fungicide?

Fungicide can be a useful preventative measure for gardeners with plants that are especially prone to rot and disease. If you’re concerned about adding chemicals to your garden, depending on the condition and the disease, there are some natural alternatives:

  • Milk is known as an effective treatment for powdery mildew. Mix a 50:50 milk to water solution in a spray bottle and apply to leaves of plants.
  • Sulfur in dust form can keep disease at bay. Be sure to apply while wearing a mask so the dust doesn’t irritate your eyes and mouth.
  • The “Cornell Formula” is a well known natural fungicide, which includes mixing 1 tablespoon baking soda, 1 tablespoon horticultural oil and 1 to 2 drops dishwashing liquid.

How to Dispose of a Diseased Plant

Many plant diseases can quickly return if the dead plant matter isn’t properly disposed of. In fact, most fungal, bacterial and viral plant diseases are spread naturally by wind currents, rain, soil seeds, insects and other animals. Others can survive on nearby dead plants or infected gardening tools. When you think you’ve collected all of the dead plant, follow these disposal tips:

  • Compost: For less persistent diseases like powdery mildew, simply removing from live plants and allow to die off in compost. If you don’t have a compost at home, check with your local government for a nearby green waster center.
  • Burial: For leaves or fruits with rot, burying the decay in a 1 foot deep hole will work.
  • Bonfires: Dry, woody material like branches can be disposed of by setting a small bonfire. Be sure to handle on a non-windy day to reduce the risk of the fire spreading.
  • Household trash: Infected bulbs, small wooden pruning and collapsed seedling can be tossed into your home garbage can.

How to Keep Your Home Vibrant

While you await the first sign of spring, browse our bright blooms to bring some sunshine inside.

Images used in graphic are courtesy of Scot Nelson and Virens.

Tiny white spots appearing on mint leaf

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more hot questions

Ask Gardenerd: Spots on My Herbs

A question came in this week to Ask Gardenerd that I have been asking myself for awhile, but never felt compelled to research the answer. Now I have no excuse:

“Hello! The leaves of many of my herbs have white speckles on them
lately. (It almost looks like they’re variegated). It’s definitely not
on the leaves, but more so ‘in’ the leaves and is appearing on many of
the varieties, such as thyme, basil, and cilantro. Any ideas on what
might be the cause? Many thanks!!”

I’ve seen this in my own garden – and this web forum not only has a great picture of the damage to several different types of herbs, but also offers a possible cause and solution:

White Spots on Herbs – take note of the homemade spray recipe listed in the forum.

It’s possible that you have either leafhoppers or thrips.

Various Leafhoppers. Photo courtesy of Illinois Natural History Research

Leafhoppers come in many shapes and colors, but they are usually small and deftly jump off your plants just when you think you might be able to catch them. They have sucking mouth-parts and can transmit diseases to plants, though most commonly they just damage them in the way you have experienced.


Image courtesy of IPM Labs

It seems like there’s a specific type of thrip for every veggie out there. I’ve experienced damage from onion thrips, found larvae on my strawberries, and obviously the herbs are well acquainted with thrips as well. They are harder to find, but the damage is easy to spot. Some of them pupate on the leaf, but most seem to reproduce and pupate on the ground.

UPDATE: It could also be spider mites. See this newsletter for a solution.


While most plants will out-produce the damage, it’s still annoying, so there are a couple things you can do:
Sticky Traps
– These yellow traps help with all kinds of small insects, including thrips and soil gnats, aphids and more.

Moisture – keeping your plants well watered will help, as thrips and leafhoppers like dry conditions.

Natural Predators – lacewings, ladybugs and parasitic wasps tackle your leafhopper problem, so plant beneficial flowers that attract them to your garden.

I hope this helps. Thanks for writing in, and keep us posted on your results.

Mealybugs: White Residue On Plant’s Leaves

Houseplants can be found in many homes and many houseplants are pretty, yet easy to care for plants. Unfortunately, due to the enclosed environment that a houseplant is normally found in, houseplants are susceptible to pests. One of those pests is mealybugs.

Does My Houseplant Have Mealybugs?

Mealybugs will commonly leave a white residue on a plant’s leaves that resembles cotton. You will find this residue mostly on the stems and leaves. This residue is either the egg sacs of the mealybugs or the pests themselves.

You may also find that the plant has a sticky residue on it. This is honeydew and is secreted by the mealybugs. It can also attract ants.

Mealybugs look like small,

flat oval white spots on plant leaves. They are also fuzzy or powdery looking.

How Do Mealybugs Hurt My Houseplant?

Besides the unsightly white residue and spots on plants’ leaves, mealybugs will literally suck the life out of your houseplant. When they reach maturity, a mealybug will insert a sucking mouth into the flesh of your houseplant. One mealybug will not hurt your plant, but they multiply quickly and if a plant is badly affected, the mealybugs may overwhelm the plant.

Mealybug Home Pest Control

If you have found the white residue on plant’s leaves that indicates a mealybug infestation, immediately isolate the plant. One mealybug home pest control is to scrape away any white residue and spots on plants leaves that you can find. Then, using a solution of one part alcohol to three parts water with some dish soap (without bleach) mixed in, wash down the entire plant. Let the plant sit for a few days and repeat the process.

Another mealybug home pest control is to apply neem oil or a pesticide to the plant. You will most likely need several treatments.

Mealybugs are damaging and difficult to eliminate, but it can be done with prompt attention to the signs of a mealybug infestation.

Powdery Mildew Treatment Indoors: How To Get Rid Of Powdery Mildew On Houseplants

It’s not talcum powder and it’s not flour. That white chalky stuff on your plants is powdery mildew and it needs to be dealt with as the fungus spreads easily. Read on to learn how to get rid of powdery mildew on your indoor plants.

Powdery Mildew on Houseplants

Powdery mildew on houseplants is a fungal disease. Initially, it produces circular powdery white spots on the foliage of plants. As the disease spreads, the entire plant material can be affected with the fluffy white fungus. Over time parts of the plant will succumb to the disease and die. It is very contagious and once one part is affected, it will infect the rest of the plant if not checked.

The fungus can affect plants outdoors, but indoor powdery mildew is more common due to conditions. The indoor powdery mildew requires temperatures around 70 F. (21 C.). It occurs when there is poor air circulation, low light, and unlike outdoor powdery mildew, thrives in drier conditions.

The mycelium formed from the fungal spores is the source of the fluffy stuff on the plant parts. The spores spread in the air

and when water splashes on plants. Powdery mildew control is essential in the home due to this aggressive, contagious state.

How to Get Rid of Powdery Mildew

The white substance rubs off easily with your fingers or a cloth. Don’t mist plants. Prevent the foliage from getting wet when watering. Keep plants spaced to enhance air flow or use a small fan to circulate the air.

Once one plant shows signs of infection, isolate it to prevent the spread of the fungus. Pinch off the affected areas and discard. Common plants affected by indoor powdery mildew are:

  • Begonia
  • African violet
  • Kalanchoe
  • Ivy
  • Jade

If powdery mildew on houseplants is present on all specimens and cultural control is not effective, advance to chemical control. Powdery mildew treatment indoors may be achieved with common household ingredients.

Water the plants well from under the foliage, then apply a spray of 1 tablespoon baking soda, 1/2 teaspoon liquid soap and 1 gallon of water. You may also add 1 tablespoon of horticultural oil to help the mixture adhere to the fungus. Apply to the top and bottom of the foliage to get all the fungal areas. Using this powdery mildew control indoors is safe and non-toxic and effective on some, but not all, species of plants.

Another organic method to try is a milk spray. Use organic milk that is free of hormones and preservatives. Mix one part organic milk with nine parts water and spray once per week on all surfaces of the plant. Provide adequate ventilation while the spray dries on the foliage to prevent mold.

Fungicides for Powdery Mildew on Houseplants

When all else fails, use a household fungicide to kill the spores and prevent the spread of indoor powdery mildew. There is some risk of toxicity in any preparation you purchase so read the label carefully and apply as the product is intended. It’s best to apply any fungicidal spray outside to prevent drift of the particles in your home.

The use of neem oil as a fungicide for powdery mildew on houseplants can also be used.

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