Concern over toxic pesticides’ affect on soil and human health is a top reason city gardeners consider organic methods of pest management. Organic pest management not only eschews synthetic pesticides, but controls pests naturally. By using integrated pest management (IPM) techniques, city gardeners can manage pests in a way that minimizes the impact on human health and the environment and uses chemicals only as a last resort.
The basic principles of IPM apply to organic city gardening but add restrictions to pesticides city gardeners can use. Organic pesticides come from natural sources like plants, fungi and bacteria. One of the primary advantages of organic pesticides is their lower residual toxicity. Most of them break down more quickly than synthetics, which can last for years.
A list of products approved for certified-organic production is maintained by the Organic Materials Review Institute (OMRI). Ideally, organic pesticides will also have low toxicity for mammals and other vertebrates, but that’s not always the case. Pesticides, organic or not, must always be used in strict accordance with label requirements. The IPM principles of careful timing and targeted application are critical with all pesticides.
Also keep in mind that a natural source does not always mean that a pesticide is benign. Some organic pesticides disrupt beneficial insects, and should be avoided. Attracting beneficial insects is actually one way to keep pests at bay.
Lacewings, known for their delicate, transparent wings, bear larvae that feed on common garden pests like aphids, mites and thrips. These larvae can consume more than 100 pests each day. City gardeners can attract them with wild bergamot, sweet alyssum and English lavender. Syrphid flies produce larvae that feed on aphids and other pests as well. Praying mantids, spiders and braconid wasps are also beneficial insects in organic gardens.
Allot 5 or 10 percent of your city garden to plants that attract beneficial insects that prey on pests. These rules vary from state to state, but in general, keep your garden as diversified as possible to attract varying types of beneficial insects.
Many beneficial insects relish plants such as those in the carrot and mint families, with clusters of tiny flowers that allow easy access to the nectar inside. They also dine on pollen, so they seek flat flowers, like those in the daisy family, which provide quick access to the pollen-filled centers. Flowers native to your area will also attract hardy beneficial insects. Check with your cooperative extension office to discover native flowers that thrive where you live.
Some plants, such as chamomile, nasturtiums and marigolds, naturally repel certain pests. Nematodes shy away from marigolds because of their roots’ slowly released natural chemicals. It’s also a good idea to intersperse your vegetable crops with companion plants like parsley, flowering dill, fern-leaf yarrow and coriander to encourage even more beneficial insects to visit.
Healthy soil produces vigorous plants that are less likely to have problems with pests. However, if your crops are attacked by pests, try organic methods like companion planting or crop rotation. At the end of the growing season, rotate crops among beds. The pests that thrive on those plants and over-winter in the soil will find their food gone when they re-emerge.
This article originally ran in Hobby Farms Presents: Orcharding.