white spots on plants

How to Get White Stuff Off Houseplants

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You may think that houseplants, being indoors, would be protected from diseases and insect pests. Unfortunately, that is not the case. Insect pests can hitch a ride indoors on other plants and pets, and some houseplants are even infected or infested when purchased. The white stuff on your houseplants is likely mealybugs or powdery mildew. The former may be confused for the latter, according to the University of Minnesota Extension website.

Identifying Mealybugs

When on a plant, mealybugs look somewhat like tiny pieces of cotton stuck to the plant. In fact, the pests secrete a cottony substance in which to lay their eggs. Mealybugs cluster along the undersides of leaves and where the leaves meet stems. These sap-sucking pests drain a plant of its juices. A few mealybugs here and there probably won’t severely affect the health of your plants, but enough of them can cause the plants’ leaves to turn yellow and drop off.

Getting Rid of Mealybugs

Chemical methods usually are not recommended for getting rid of insect pests, especially on houseplants. Light infestations of mealybugs can be removed by picking them off the plants. Kill them first, if you prefer, by dipping a cotton swab in rubbing alcohol and dabbing the swab on the mealybugs. Because rubbing alcohol may damage or discolor some plants’ leaves, test it on an inconspicuous portion of a plant’s leaf before you use it on another portion of the plant. If a plant is heavily infested with mealybugs and is very weak or damaged as a result, then simply throwing away the plant may be the best option.

Identifying Powdery Mildew

Powdery mildew is a fungal disease. It usually appears in winter on plant leaves and flowers. Signs of the disease first appear as small, white spots that quickly grow and merge. Entire leaves may be covered with the thin, white layer of fungus, which may be mistaken for dust. Unlike dust, however, simply wiping off the substance is not enough to help an affected plant.

Getting Rid of Powdery Mildew

As with insect pests, chemical controls are not recommended for use in getting rid of powdery mildew, especially on indoor plants. Move an infected plant away from nearby plants, and then remove infected parts of the solitary plant. As you clip off infected leaves and/or stems, dip your cutting tool into bleach to disinfect it. Taking that measure helps to prevent the fungus from spreading to other parts of the plant. If an infection is severe, the plant may need to be thrown away, according to the Purdue Plant and Pest Diagnostic Laboratory website.

How to Get White Stuff Off Houseplants. You may think that houseplants, being indoors, would be protected from diseases and insect pests. Unfortunately, that is not the case. Insect pests can hitch a ride indoors on other plants and pets, and some houseplants are even infected or infested when purchased. The white …

How to Prevent Powdery Mildew on Plants Using Baking Soda

A Home Remedy for Fungus Diseases

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The Spruce / Cori Sears

Powdery mildew is one of the most commonly occurring plant problems.   It is a fungal disease that affects plant leaves and stems, coating them in what looks like a white or gray powder-like substance. In severe cases, powdery mildew can even spread to the buds, flowers, and fruits of plants. Although any plant can get powdery mildew, some are very susceptible—such as crab apples, cucumbers and all types of squash, lilacs, phlox, and roses.

The white coating greatly diminishes the appearance of the plant, but it is not fatal unless left uncontrolled.   However, as it spreads, it stresses and weakens the plant and makes it hard for photosynthesis to occur. Left untreated, powdery mildew can leech nutrients from the plant, cause leaves to yellow and wither, exposing fruit to sunburn. It can even affect the flavor of fruit and reduce blooms on plants. Most importantly, powdery mildew on one plant can quickly spread to other plants, so it’s important to prevent its spread.

Controlling Powdery Mildew With Baking Soda

Baking soda alone isn’t effective in controlling powdery mildew, but when combined with liquid, non-detergent soap and water, it works well as a preventative. If you know which plants are susceptible, spraying them weekly with the baking soda/soap recipe (and reapplying after rain) can greatly reduce the incidence of powdery mildew in your garden. Powdery mildew typically occurs in late spring/early summer.   New foliage is especially susceptible to the fungus, which, unlike other mildews, occurs in moderate temperatures with warm days/cool evenings, low light, high humidity–but dry foliage. Spacing plants for good air circulation also helps prevent the spread of powdery mildew.

To control powdery mildew on plants, mix together the following:

  • 1 tablespoon of baking soda
  • 1/2 teaspoon of liquid, non-detergent soap
  • 1 gallon of water

Pour the mix into a sprayer, and evenly coat all areas of the plant, including the underside of leaves and stems.

Do not store unused mixture. While this recipe has been known to be effective, it can burn the leaves of some plants. It is recommended that you water your infected plants well a couple of days before applying this mixture and don’t apply it in full sun. Try on a small area first to test the plant’s response before spraying the entire plant.

The soap helps the mix spread and cling to the leaf surface.

Control Versus Cure

Unfortunately, this baking soda mixture works best as a preventative, applied before powdery mildew has a chance to spread on your plant. It is less effective as a cure once the fungus has taken hold. If you know a plant is affected by powdery mildew year after year, as is the case with many monarda, phlox, and lilacs, then spraying early in the season may prevent any occurrence that year. In the first signs of infection on a plant, remove the leaves with powdery mildew, if there aren’t too many, and spray the rest of the plant. Spray any susceptible plants located nearby, too.  

Additional Uses?

Researchers are still studying the effects of using a baking soda mixture on other fungal diseases such as black spot, rust, and anthracnose.

Powdery mildew, a plant fungus disease, has long been controlled with a home remedy of baking soda, water, and soap.