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March 6, 2018 > Pick predators over pesticides

Pick predators over pesticides

By Daniel O'Donnell

Trees, plants, animals, insects, and microorganisms work symbiotically to create a healthy forest. Introduce a bark beetle that has few local predators and the balance of the ecosystem can be tipped to a point that jeopardizes the forest's survival. The healthiest home gardens also have balanced ecological communities that are vital to the overall urban environment. Introducing pesticides can threaten and even destroy a home garden ecosystem. It is beneficial and rewarding to help create a healthy environment by attracting or introducing some animals and insects that curtail the need for pesticides.

A conventional pesticide is usually a manufactured chemical compound used to kill organisms considered to be pests. Pesticides create problems for organically-minded gardeners who want to eliminate or reduce toxic chemicals from their environment; support habitats for bees, butterflies, and other beneficial insects; and protect their plants. Organic pesticides are naturally occurring substances used to target pests. But even an organic pesticide can cause collateral damage to a garden's ecosystem.

An ecosystem-based strategy called Integrated Pest Management (IPM) uses a combination of techniques for long-term prevention of pests. The goal is to minimize risks to humans and all other non-targeted organisms in the environment. Broad spectrum pesticides should never be used in an IPM approach. They can be toxic to all the organisms, pests and beneficials in the garden and the soil. The use of a pesticide that is effective on only the targeted organism is better, and the nonuse of pesticides is best.

One of the ways an IPM approach accomplishes the nonuse of pesticides is by introducing what are referred to as biological controls or Ònatural enemies.Ó These organisms can be predators that feed on pests. It is always a pleasant surprise to see them and understand just how diverse an urban garden can be.

There is no insect that people find more charming and beautiful than a lady beetle. Lady beetles and their larva are generalist predators preying on soft-bodied insects and insect eggs. They particularly like to feed on aphids and whiteflies, which are common pests that plague Bay Area gardens. Packages of lady beetles can be purchased at most garden centers. They can be drawn to a garden by using Monterey Lady Bug Attractant that contains alluring pheromones.

Anyone lucky enough to live near water or have a pond is unlucky enough to have mosquitoes, unless there are dragonflies around. A dragonfly can eat a third of its weight per day. Although they eat a variety of insects, an overwhelming number of their prey are mosquitoes since both live near water. Dragonflies begin their lives as aquatic nymphs feeding on mosquito larvae as one of their primary food sources. They can be attracted to a garden by keeping plants in water features and planting around the edges.

There are a surprising number of praying mantises that live in Bay Area gardens. These highly successful camouflaged hunters sit patiently with their large front legs bent at an angle that suggests they are praying. They are generalist predators and will eat insect populations, helping to keep them at a manageable level.

Find a yard with rock clusters and sunlight, especially near the East Bay hills, and there will be blue belly or fence lizards. They feed primarily on insects but play a more beneficial role in pest management. Ticks are a major pest because they carry Lyme disease. Ticks commonly feed on lizard blood that kills the bacterium that causes the disease. Sometimes fence and blue belly lizards can be purchased at local pet stores or easily captured in a neighbor's yard and then released into a garden.

An urban garden can provide a buffet for snails and slugs. A novel way to rid the garden of them is to introduce box turtles to the yard. Box turtles will quietly roam day after day in search of snails and slugs. The yard needs to be fenced in because they will migrate. Raccoons put them at risk, so they will need plenty of places to hide at night.

Evening provides a quiet time for pests to invade a yard. Fortunately, opossums are nocturnal. So are snails and slugs, making an opossum's search for them a little bit easier. Opossums are no threat to plants, vegetable crops, or pets except smaller chickens, which should be locked up at night anyway. Larger than rats, their bodies require more nourishment and thus greatly reduce food sources that attract rats.

The night skies are abundant with flying insects. A single bat can eat 6,000 to 8,000 mosquito-sized insects per night. Their diet includes termites, crop-destroying moths, gnats, flies, mosquitoes, and cucumber beetles. Bats can be attracted to a garden by building a Òbat box,Ó which provides a safe home for them. Bat box building instructions can be found at Bat Conservation International's website, www.batcon.org.

There is no reason why an urban home garden cannot be a thriving self-regulating ecosystem. Using natural enemies instead of pesticides is safer alternative for everyone and everything, except the pests.


Daniel O'Donnell is the co-owner and operator of an organic landscape design/build company in Fremont. www.Chrysalis-Gardens.com

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