JESSICA DAMIANO The Associated Press
Imagine this: You have planted milkweed, bee balm or California lilac and are happy to see bees and butterflies fluttering around in your garden. They are comfortable feeding pollinators and love the life these plants attract to your garden.
As you stroll past your beds to check on your tomatoes, you notice that they are covered in black dots. Upon closer inspection, it turns out that your plants are affected by aphids.
If you instinctively want to reach for a chemical pesticide – stop. Although it might eliminate your aphid problem, it will also threaten beneficial insects that pollinate plants and keep pests under control. Instead, apply the principles of Integrated Pest Management or IPM.
The practice begins with accepting that a certain pest presence is tolerable. Only when this threshold is exceeded should an inspection be considered. Your first line of defense should always be the most benign method available. Common sense applies here, which should apply both in the house and in the garden.
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Take my basement: Every spring the ants come marching in, but instead of spraying the perimeter of my house with a pesticide, I put ant traps wherever I see activity. After a few days, the colony collapses and the problem is solved.
All butterflies start out as caterpillars, and all caterpillars chew on plants. Therefore, I consider any plant that doesn’t have at least some holes in its leaves to be useless to the ecosystem. Tolerate some leaf munching and let nature take its course.
Back to your tomatoes: IPM would mandate washing off aphids with a strong jet of water. It usually works. But if they keep coming back after multiple attempts and you feel you need to escalate, take small steps.
In this case, the next step would be an insecticidal soap, a non-toxic pesticide that’s safe for humans, beneficial insects (after drying), and most plants (read the label to make sure your plant isn’t one of the few who are sensitive to the product).
As a rule, prevention is the best treatment. Examine plants—even under their leaves—before you bring them home from the nursery. Reject anyone showing signs of disease or infestation.
Forego instant gratification and place plants appropriately to accommodate their adult size. Overcrowded plants retain moisture and encourage mold, mildew, and fungal diseases.
Practice good hygiene by regularly removing the plant’s fallen leaves, fruit, and debris, which invite insects, rodents, and pathogens if they are allowed to remain on the ground.
If you see pests like aphids, wash them away. Blot scale insects with a cotton swab dipped in rubbing alcohol. Hand-pick tomato hornworms and cabbage worms (unless they’re covered in the white eggs of braconid wasps, which are little parasite killers that do the killing for you).
Traps can be used to catch snails. Place shallow beer containers around affected plants or place small wooden planks on the surface of the soil overnight. Chances are you have a jar full of drowned snails – or a collection of live snails under the boards – to dispose of in the morning.
If you decide a pesticide is necessary, choose it carefully and follow label directions and precautions. Avoid using pesticides in extreme heat, on windy days, or when crops are damp, and only apply early in the morning or at night when pollinators are dormant. It might hurt, but consider removing blooms from the plant to reduce the risk to beneficial insects that forage for pollen and nectar. In most cases, more buds will come.
These pesticides are generally considered safe for pollinators when used correctly:
insecticidal soap is a non-toxic option that kills aphids, adelgids, lace bugs, leafhoppers, mealybugs, thrips, scale insects, sawfly larvae, spider mites and whiteflies by suffocation rather than poisoning. It has to be sprayed directly on the insects and loses its effect after drying.
garden oil, another smothering agent, is effective against adelgids, aphids, leafhoppers, mealybugs, mites, scale insects, spider mites, thrips and whiteflies. The product must come into direct contact with insects when wet and becomes safe for beneficial insects (and ineffective against pests) once dry.
neem oil, a pesticide derived from the seeds of the neem tree is effective against aphids, adelgids, beetles, borers, leafhoppers, leaf miners, mealybugs, scales, tentworms, thrips, webworms, weevils and whiteflies.
Bacillus thuringiensis (Bt) is a naturally occurring soil bacterium used as a pesticide. Several strains are available, each targeting different pests. So read the label to make sure the product you are buying is right for your needs. Some strains are toxic to monarch butterfly caterpillars, so don’t apply them on or near milkweed, which is their only food source.