Home & Garden

Pest management and a healthy garden

Ladybugs and tansy flowers help to keep your garden pest free.

The benefits of choosing a less-toxic approach for pest control are plentiful: a more healthful home for you, your kids, and pets; an ecologically balanced garden where less pest control will be necessary in the future; and a clear conscience from doing your best to reduce pollution. Everything done in a garden environment will eventually have an impact on the garden’s pest population. Resistant, suitable plants and good soil and plant care are powerful preventive measures.


A healthy garden filled with a variety of flowering plants will be significantly more resistant to pest and disease damage. Diversity will also help attract beneficial creatures to your garden, creating a balanced ecosystem and reducing the need for chemical controls. Also, if you should have a pest problem on one type of plant it will not decimate your entire garden.

Pest insects have always been with us and so have beneficial insects to maintain the balance of nature. They fill two main roles in the garden ecosystem: pollinators of plants and predators of pest insects.

The first step in attracting beneficial insects is to reduce or eliminate the use of broad-spectrum pesticides. Not only will your garden be free of chemical residue, but birds, pollinators (like bumblebees), and good insects are often more susceptible to pesticides than the insects you are trying to eliminate.


Ladybugs add attractive color to a garden while fighting pests. Release them at night (so they don’t fly away), at the base of plants. They naturally climb up plants and will eat aphids, mealy bugs, leaf hoppers, and other destructive insects. They continue until the bad guys are gone, laying their own eggs in the process. When new pests arrive, fresh ladybugs will be waiting.

Praying mantes eat a wide variety of insects — virtually any pest that moves. Since they don’t fly, they stay in the area where they are released. Beneficial nematodes assault flea larvae in the soil, bark, or ground litter. They also attack more than 200 kinds of garden pests.


Like people, plants favor some companions over others. Some plants emit poisons, called phytotoxins, that can stunt or even kill nearby plants. Other plants thrive in each other’s company. Companion planting is the art (or science, if you will) of planting mutually beneficial plants together. Here are a few time-tested combinations:

  • Rosemary, sage, and thyme planted among cabbage plants repel cabbageworms.
  • Marigolds planted thickly around roses will help repel aphids, will keep Colorado potato beetles away from potatoes, and repel rabbits from your garden.
  • Radishes planted among cucumbers discourage cucumber beetles.
  • Tomato plants keep asparagus beetles away from asparagus.
  • Potato plants keep Mexican beetles away from beans.
  • Tansy keeps many insect pests away.
  • Garlic plants keep aphids away.


Mosquitoes have long been an annoying summer pest. With the Zika virus outbreak, concern for mosquito control has intensified. Mosquitoes thrive in dark, wet areas, so be sure to empty any standing water that may accumulate in your yard.

A natural biological control, Bacillus thuringiensis is a bacterium that attacks mosquito larvae, but not beneficial insects, and is harmless to other living things. Float a biodegradable Mosquito Dunk in water troughs, koi ponds, birdbaths, rain barrels, or wherever water collects and remains for periods of time. As the Dunk slowly dissolves, it releases a bacterium toxic to all mosquito larvae species. When the larvae hatch and begin to eat the bacterium, it will kill the mosquito larvae before they can grow up to become biting and disease-spreading adults. Each Dunk lasts 30 days or more.


If you have indoor pest problems with cockroaches, ants, or other insects, deny them access to your home and the food and water they seek with these best practices:

  • Store food in the refrigerator or tightly sealed containers.
  • Keep your home clean and tidy. Thoroughly clean counters and floors daily in eating and food preparation areas. Don’t leave dirty dishes out overnight.
  • Remove compost containing food scraps nightly.
  • Clean recyclables before storing them. At night, place pet food and water bowls in a moat of soapy water.
  • Keep areas dry. Fix leaky plumbing.
  • Seal cracks and crevices. Caulk and paint cracks around baseboards, cupboards, pipes, sinks, and so forth. Use mildew-resistant caulk in moist areas.
  • Weather-strip around doors and windows, and repair holes in screens.

Remember: If you must use a pesticide, look for the least toxic option, and do not put pesticides in the trash. Dispose of pesticides at the San Francisco Household Hazardous Waste Facility (501 Tunnel Avenue, 415-330-1400). To schedule a free pick-up, visit or call 415-330-1405.


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