Protect your plants from spider mites and whiteflies

June 23, 2015

Spider mites and whiteflies attack fruit trees, shrubs and indoor and outdoor plants. But there are some easy ways to keep the pests at bay and protect your plants.

Protect your plants from spider mites and whiteflies

Dealing with mites

Minuscule mites — called two-spotted spider mites, red mites and simply spider mites — attack fruit trees, shrubs, houseplants and greenhouse plants.

  • Although nearly invisible to the eye, they make themselves known by tiny webs on the undersides of leaves, as well as by leaves that are curled and greyish; the leaves usually become speckled with tiny yellow and brown dots.
  • If the infestation is severe, leaves and buds will fall off, and the plant will die.

Here are some ways to spot and control spider mites around your plants.

Do a test

Hold a sheet of white paper under a plant and tap the leaves gently. Any red spider mites will show up on the paper as little moving dots.

Know their favourite outdoor plants

Favourite outdoor targets include cucumbers, beans and strawberries. Hawthorns, rosebushes and other shrubs are also affected, as well as many annual flowers.

Encourage natural predators

  • Allow natural predators, such as ladybugs, green lacewings or Amblyseius californicus (a predator mite) to control outdoor infestations.

When impatiens or other temporary plants become infested, dispose of them before the mites spread to more long-lived plants.

Wet your plants

Spider mites thrive in dry, dusty conditions, which some mite predators dislike.

  • Invite predators by misting plants early in the morning, every three days.

Give plants a buttermilk bath

Many gardeners swear by a buttermilk spray as a defense against mites. Mix 125 millilitres (1/2 cup) of buttermilk, 800 millilitres (3 1/2 cups) of wheat flour and 19 litres (five gallons)of water and slather it on the undersides of infested leaves.

Don't handle clean plants

  • Avoid touching clean plants after you've touched infested ones, and never use a feather duster to clean houseplants.
  • Either action can spread mites from plant to plant.

Dealing with whiteflies

Tiny whitefly adults — about two millimetres long — resemble moths with white, powdery wings.

  • Shake a suspect plant.
  • If a white cloud rises, the plant has whiteflies. Here are some ways to eliminate the population.

Watch for whiteflies outdoors

As soon as the weather warms, keep an eye out for whiteflies outside.

  • They attack many vegetables and flowers.
  • Indoors, look for them in fall, when they come in from the cold; they particularly like chrysanthemums and poinsettias.
  • Affected plants have yellowing, sticky foliage and may become covered with black mold that grows on the honeydew secreted by whiteflies.

Make homemade sticky traps

Don't waste money buying yellow sticky traps to catch whiteflies.

  • Instead, make your own by coating yellow construction paper with petroleum jelly.
  • Place the traps on sticks on the ground a few inches from plant foliage or hang them over trays of seedlings or infested houseplants.

Use plants to attract and repel

  • Nicotiana or catnip (Nepeta cataria) lures whiteflies away from other plants, where you can destroy them.
  • To repel whiteflies, plant some marigolds or nasturtiums among more susceptible plants, such as salvias.

Make your own solutions

  • Control whiteflies on houseplants by wiping the leaves with cotton dipped in diluted rubbing alcohol.
  • You can also spray with insecticidal soap, pyrethrum or a solution made by mashing garlic cloves in water.

Suck them up

Use a small handheld vacuum to suck whiteflies off leaves — or even out of the air as they hover over plants.

The right tools

Using traps, tricks and the right plants, you have to the tools you need to fight whiteflies and spider mites, whether they're attacking your house plants or your garden.

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