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Control Garden Pests with Inexpensive, Safe Methods

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May is here, which means it’s time to start thinking about the best ways to battle the insects and diseases that plague us gardeners once temperatures start to rise. These days, I go for simple, cheap and safe.

Here are a few favorites:

Water. Starting in spring when those pesky aphids start to appear, get in the habit of giving aphid-prone plants (can you spell r-o-s-e-s?) an all-over blast of water in the morning. A hard spray, including the undersides of leaves, knocks off and often kills soft-bodied insects on plant surfaces such as aphids, mites and thrips. The trick to this tactic is commitment; it won’t control the populations unless you do it every day. Spraying in the morning ensures plenty of time for the moisture to evaporate, which will help avoid molds and fungus.

Vegetable Oil. There is something you can do with inexpensive veggie oils. First, fill an empty tuna can about three-quarters full, add a scrap of any kind of leftover meat, then set the can next to any plant that has been plagued by earwigs or slugs. They climb into the can and drown in the oil.

Copper. Wrapping copper foil or flashing around tree, shrub, and woody perennial trunks and planter boxes will keep snails away for years. According to the UC Davis Integrated Pest Management (IPM) program, “It is believed that copper barriers are effective because the copper reacts with the slime that snails and slugs secrete, causing a disruption in their nervous system similar to an electric shock.”

Plastic Sheets. Using heavy, clear plastic sheets to solarize soil not only kills harmful soil-borne pests, but also kills many weeds, pathogens and nematodes, making way for beneficial microorganisms to quickly repopulate. On top of that, solarization actually improves soil, say the experts at UC IPM. “It can improve soil structure by increasing the availability of nitrogen and other essential nutrients for growing healthy plants. Plants often grow faster and produce both higher and better-quality yields when grown in solarized soil. This can be attributed to improved disease and weed control, the increase in soluble nutrients, and relatively greater proportions of helpful soil microorganisms.” Solarization involves heating the soil by covering it with a clear plastic tarp for four to six weeks during a hot period of the year when the soil will receive the most direct sunlight. When done properly, solarization will kill soil-borne pests up to 18 inches deep.

For more details about these and other simple, environmentally friendly pest and disease controls, visit, the UC Davis Integrated Pest Management website.

Rachel Oppedahl is a University of California Cooperative Extension Master Gardener of Tuolumne County.