Pest and weed control in the sustainable garden or farm plot primarily involves improving the health of the plants and soil so they can better resist damage (see References 2, page 446). However, in even the healthiest gardens, the occasional pest or weed problem can jeopardize plants. Sustainable gardeners and farmers have an arsenal of pest- and weed-control tactics that don't involve the use of synthetic chemicals --- an approach known as integrated pest management (see References 4).
In nature, predators, parasites and pathogens keep pest populations at manageable levels. When your garden lacks these natural defenses, your plants become increasingly susceptible to pest damage. Sustainable agriculture and gardening often calls on "natural enemies" to keep pest populations down, according to the University of California Statewide Integrated Pest Management Program. Maintaining a diverse landscape with abundant flowering plants to feed and shelter pest predators helps increase the population of species like ladybugs, lacewings and predatory wasps. When adding a predator species such as predatory mites, make sure your garden has appropriate habitat to retain these predators, or the pest control relief is only temporary. For some pests, you can apply a disease or parasite to your garden that kills the pest species while leaving beneficial insects alone. Examples include parasitic nematodes, Bacillus thuringiensis (Bt) and viruses. (See References 1)
Traps and Barriers
Barriers deny pests access to your plants, with several methods described in "Rodale's Ultimate Encyclopedia of Organic Gardening." For example, floating row covers prevent bean beetles from damaging your plants; however if the plant requires cross-pollination --- as do cucumbers and squash, for instance --- you'll need to remove the cover during periods of pollinator activity. Cardboard collars around seedlings prevent cutworms from destroying the plants. Sticky traps and pheromone traps attract pests, then do not allow their escape. "Rodale's" says that in addition to controlling pests, traps help you to monitor pest populations in your garden. (See References 2, pages 451-456, 520)
Mechanical Weed Control
All gardeners are familiar with the techniques of hand-pulling, hoeing and tilling weeds to control weeds early, in the seedling stage, and before they go to seed. Bare ground invites weeds to germinate; "Rodale's" notes that placing a layer of mulch not only reduces weed germination but reduces soil erosion and run-off, and increases levels of soil organic matter. In the off-season, mulches and cover crops keep your soil protected and weed-free. (See References 2, pages 651-654)
Some naturally occurring compounds control weeds, and two noted by the National Sustainable Agriculture Information Service are ones you may even find in your pantry. Corn gluten meal acts as a preemergence herbicide for lawns and agricultural crops, destroying weeds before they germinate. Vinegar, even 5 percent household vinegar used in cooking, can destroy the foliage of above-ground weeds. Herbicidal soaps made from fatty acids and herbicides made from plant extracts are available as commercial products to control weeds. (See References 3)
- University of California Statewide Integrated Pest Management Program; Biological Control and Natural Enemies; S. H. Dreistadt; November 2007
- "Rodale's Ultimate Encyclopedia of Organic Gardening"; Fern Marshall Bradley, et al., editors; 2009
- University of Minnesota: IPM Defined
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