Pests in Gardens and Landscapes: Quick Tips


Published   6/23

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Rose aphids on young blossom.

Rose aphids on young blossom.

Mummified aphids that were parasitized by a wasp.

Mummified aphids that were parasitized by a wasp.

Lady beetle larva eating an aphid.

Lady beetle larva eating an aphid.

Most plants have one or more aphid species that feed on it, but feeding usually does not damage or kill established plants. Aphids can curl leaves and produce sticky honeydew that may attract ants and sooty mold. Aphids have many naturally occurring predators and parasites that feed on them. On sturdy plants, aphids can be knocked off with a strong stream of water. When aphid numbers are high and other control methods aren’t effective, pesticides such as insecticidal soaps and oils are available.

Aphids are common in gardens and landscapes.

  • Aphids feed on soft, new plant growth. Protect young plants. Don’t over fertilize; use organic or slow-release products.
  • Aphids build up on flowering plums, roses, tulip trees, crape myrtles, apples, and many vegetables. Expect aphids when you grow these plants.
  • Most established plants can tolerate aphid feeding and will outgrow any damage.

How can I reduce aphid numbers?

  • Prune infested leaves and stems.
  • Knock aphid populations off plants by shaking the plant or spraying it with a strong stream of water.
  • Protect seedlings with covers or aluminum foil mulches.
  • Wait for hot weather; some aphids are heat-intolerant and will be gone by mid-summer.

Are there any good bugs that will eat aphids?

Naturally occurring insect predators such as lady beetles and lacewings will visit plants when aphids are abundant. The larval, or immature stage, of these “natural enemies” most often feed on aphids. Ants protect aphids from natural enemies. Keep ants off plants to help beneficial insects do their job. Encourage natural enemies by avoiding the use of broad-spectrum insecticides that can be toxic to them and by planting flowering plants that provide nectar and pollen for them. Common natural enemies of aphids include:

  • Lady beetles (ladybugs
  • Lacewings
  • Syrphid fly larvae
  • Soldier beetles
  • Tiny parasitic wasps that turn aphids into crusty, round “mummies”

What about pesticides?

  • Use nonchemical methods first to manage aphid populations.
  • If insecticides seem necessary, choose products that are less toxic to natural enemies, such as commercially available insecticidal oils and soaps. When properly used, these materials solve most aphid problems.
  • Oils and soaps work by smothering aphids, so apply these products thoroughly. Don’t apply them to drought-stressed plants or when it is very hot. Some plants are sensitive to these products.
  • Aphids hidden within curled leaves will not be affected by pesticides that work on contact. Prune these out.
  • Systemic insecticides can kill hidden aphids, but they are much more toxic and might also harm bees and other beneficial insects on flowering plants.

Read more about Aphids.

Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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