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LifestyleColumnistsJessica Damiano

How to control scale insects on houseplants

Scale infests a gardenia plant. Persistence is necessary

Scale infests a gardenia plant. Persistence is necessary to control it. Credit: Kim Clarke

DEAR JESSICA: I have a gardenia plant that I am attempting to overwinter indoors, but it has developed a white substance on the leaves. I also noticed quite a few ants nearby. I’m not sure what this is or what I can do to save the plant. I water it regularly and have a humidifier nearby to try to mimic a more tropical environment. Any suggestions would be greatly appreciated.Kim Clarke, Smithtown

DEAR KIM: The bumps you’re seeing on leaves (and perhaps on stems, as well) are scale insects. Gardenias are notoriously susceptible to such an infestation.

Scale are insects with piercing and sucking mouthparts that penetrate plant tissue and extract sap and other fluids. Then, as if that weren’t bad enough, they excrete a sticky substance called honeydew all over a plant, attracting ants, which feed on it. To make things worse, black sooty mold grows on honeydew, so leaves and stems often become coated, not to mention ugly.

To understand how to control them, you first need to understand their life cycle. Scale emerge as nymphs in spring, mature and mate during summer, and give birth in time for Labor Day. Those crawling newborns develop into nymphs that attach themselves to plant parts, where they quietly spend winter, which is what you’ve noticed. In spring, they’ll repeat the cycle — unless you stop it.

The easiest way to lessen their numbers and possibly eradicate them (fingers crossed!) would be to scrape them off gently using the side of a dull blade, such as that of a butter knife, and discard them in the trash. Then rinse honeydew and sooty mold off leaves and stems with water, rubbing gently if necessary.

Because you mentioned overwintering the plant indoors, I assume you intend to return it outdoors when weather permits. Keep an eye on it over summer, and if you spot any activity, be prepared to spray the plant in late August or early September, when the next crawlers would develop. The crawling stage is the only stage that is susceptible to insecticides. At that point, apply neem oil, mixing and spraying according to package directions, taking care to coat the entire plant (tops and bottom of leaves as well as stems). Only use neem oil when the temperature is below 80 degrees; repeat once a week for four weeks or until you no longer see any insects.

DEAR JESSICA: I have several large trees on my property that are over 40 feet tall. In addition, my house faces east so the afternoon sun is blocked by the house. I’m having a tough time maintaining a nice lawn because of all the shade. I have in-ground sprinklers so water is not the problem. Any ideas?— Joel Beja, Commack

DEAR JOEL: The problem clearly is a lack of sufficient sunlight and, unfortunately, there is no grass variety that will grow thick and lush in deep shade (fine fescue can handle some shade if the soil is well-drained).

So, unless you’re willing to severely prune or remove the trees altogether, my recommendation would be to plant shade-loving ground cover, such as pachysandra, dead nettle, periwinkle or sweet woodruff. You might even incorporate all of them and plant hostas around the trees for more interest, turning the lawn area into a shade garden.

DEAR JESSICA: When is the best time to apply pre-emergents for crabgrass?— Larry Shivers, TK

DEAR LARRY: Pre-emergents such as Preen and corn gluten meal (a natural alternative) prevent the germination of crabgrass (and other seeds) if applied during the window of time between when the forsythia begins blooming and the lilacs fade on your side of the street; note that the flowers may be on a slightly different schedule across the street because of differing sunlight exposure.

Don’t apply any pre-emergent if you’re also sowing grass or other seeds, or if you’re depending on self-sowing annuals to take hold; it will inhibit them, as well.

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