Plan the perfect garden with our interactive tool →

White Powdery Spots on a Meyer Lemon Tree

mucella/iStock/Getty Images

Looking more like oranges than lemons, Meyer lemons (Citrus x meyerii) offer a sweeter, less-acidic thinner-skinned alternative to their mouth-puckering, sunny-yellow relatives. Suitable for U.S. Department of Agriculture plant hardiness zones 9 through 11, Meyer lemons grow on compact trees with white blossoms and yellow-orange fruit glowing against their glossy, deep-green leaves. They paint a pretty picture, unless white powdery spots arrive to spoil it. Treating the disease or insects responsible is relatively easy.

Powdery Mildew Fungus

Powdery mildew disease occasionally blemishes Meyer lemon's leaves and fruit with white, talcum-powder textured spots. An airborne fungus partial to cool, dry conditions, it's most active between 60 and 80 degrees Fahrenheit.

Powdery mildew only attacks living plant parts. Affected leaves are likely to die and fall from the tree more quickly than uninfected ones.

Managing Powdery Mildew

Powdery mildew spores don't survive long when the sun raises leaf temperatures above 95 F. Planting a Meyer lemon where it gets gets six hours of daily sun may be enough to thwart an infection.

For organic, bee-friendly control of existing powdery mildew, thoroughly coat the leaves with a spray solution of 1 part raw or skim milk to 9 parts water. Weekly treatments when conditions favor the disease reduce symptoms by up to 90 percent, reports the National Gardening Association.

  • Powdery mildew disease occasionally blemishes Meyer lemon's leaves and fruit with white, talcum-powder textured spots.
  • An airborne fungus partial to cool, dry conditions, it's most active between 60 and 80 degrees Fahrenheit.
  • Powdery mildew only attacks living plant parts.
  • Affected leaves are likely to die and fall from the tree more quickly than uninfected ones.

Citrus Mealybugs

The insect version of wolves in sheep's clothing, mealybugs conceal themselves beneath layers of fluffy white wax, sink their sharp mouth parts into plants and drain them of sap and vigor. From a distance, they look like bits of cotton wool glued to the stems and leaves. A severely infested Meyer lemon may weaken and drop its fruit prematurely.

An early and obvious sign of mealybug infestation is honeydew, the bugs' sticky, transparent waste. Sooty mold spores cover honeydew-coated leaves in layers of greasy, black fungus and may interfere with photosynthesis.

Mealybug Control

Rinsing an infested Meyer lemon down with a sharp blast of hose water every few days may be enough to manage the problem. Regularly wetting the leaves also kills powdery mildew spores.

Ladybugs, green lacewings and syrphid flies all prey on mealybugs. To lure them to your tree, plant nectar-and pollen-producing flowers nearby.

The beneficial bugs seek out shallow-faced flowers such as sweet alyssum (Lobularia maritima), perennial in USDA zones 5 through 9, or wild bergamot (Monarda fistulosa), which grows in USDA zones 3 though 9.

If these methods don't keep the mealybugs in check, use organic, ready-to-use insecticidal soap. In the early morning or after sundown, when honeybees aren't foraging and no sun is on the tree, spray until all the tree's surfaces drip with the soap.

Repeat the application every two to three days, or at the label's suggested intervals, until the infestation is small enough for predators to control. Dress in protective clothing and eyewear and follow the label's application instructions when working with any insecticide.

  • The insect version of wolves in sheep's clothing, mealybugs conceal themselves beneath layers of fluffy white wax, sink their sharp mouth parts into plants and drain them of sap and vigor.
  • If these methods don't keep the mealybugs in check,* use organic, ready-to-use insecticidal soap.
  • In the early morning or after sundown, when honeybees aren't foraging and no sun is on the tree, spray until all the tree's surfaces drip with the soap.

Related Articles

Little White Bugs on Orchids
Little White Bugs on Orchids
How to Get Rid of the Insects on Your Lemon Tree
How to Get Rid of the Insects on Your Lemon Tree
Whitefly Control on Citrus Trees
Whitefly Control on Citrus Trees
White Fungus on a Japanese Maple
White Fungus on a Japanese Maple
How to Treat Powdery Mildew on Begonias
How to Treat Powdery Mildew on Begonias
How to Identify Lemon Tree Pests
How to Identify Lemon Tree Pests
Aphids on Succulents
Aphids on Succulents
Bugs on Plumeria Plants
Bugs on Plumeria Plants
How to Treat Orange Trees for Pests
How to Treat Orange Trees for Pests
How to Kill Whiteflies on Gardenias
How to Kill Whiteflies on Gardenias
Homemade Organic Pesticide for Fruit Trees
Homemade Organic Pesticide for Fruit Trees
Neem Oil for Spider Mites
Neem Oil for Spider Mites
Basil Plant and Mites
Basil Plant and Mites
Causes of Small White Spots on Tomato Plants
Causes of Small White Spots on Tomato Plants
Garden Guides
×