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  • How do I kill aphids, but not lacewings?

    Created by Cindy Wittmier on

    I have a 22′ geodesic dome greenhouse with many green lacewings that have emerged and seem to be recycling on their own for the past 6 months.

    My question; how do I kill aphids without harming my beneficial insects. Will diatomaceous earth kill beneficial insects? I still have a very uncontrollable aphid infestation yet have released lacewing larva by the 1000’s.

  • Author
  • #263810 Reply

    E. Vinje

    Hi Cindy –

    Diatomaceous Earth is made from the fossilized remains of tiny freshwater algae-like creatures called diatoms. A mild abrasive, it kills insects pests, including aphids, within 48 hours of contact. It’s not a poison, but works by scoring an insect’s hide as it crawls over the powder. Unfortunately, this would include any soft-bodied lacewing larvae that may crawl through it.

    To kill aphids, but not beneficial insects, we recommend providing stable, continuous suppression of pests by promoting their natural enemies. This long term approach is also the least toxic method of controlling insects.

    1. Do a little reading on common insect pests of the plants you want to grow. Field scout and monitor with traps to identify pests. Learn the pest’s life cycle so that treatment can be chosen and timed to be most effective.

    2. Establish a level of acceptable damage.

    3. Monitor the pest situation regularly. Only when monitoring has indicated that the pest will cause unacceptable damage should treatment be considered.

    4. If pest populations are high, use a least-toxic, short-lived organic pesticide (Safer® Soap is a favorite!) to establish control while reducing damage to pest predators and the environment. Spot spray problem areas, especially new growth, and stay vigilant. Eventually your lacewing population will gain the upper hand.

    Hope it helps!

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