Tips for Preventing Garden Pests and Diseases

Growing healthy plants is the first step toward a great garden. In order to achieve this, it's important to prevent diseases and pests through careful plant selection, planting, and care. It also helps to use some of the new environmentally safe products and techniques described in this article. We'll start by taking a closer look at how to prevent disease from penetrating your garden.

  • Among the most important considerations when preventing diseases is soil drainage; soggy roots lead to rot in almost every instance (though there are some plants that need the extra water). Sunlight is also essential. It must keep the plant well nourished (by photosynthesizing) so it can stay robust enough to resist diseases that attack weak plants.

  • Plants with enough space to reach maturity without overcrowding are likely to be healthy. They suffer less competition with their neighbors for sun, water, and nutrients, and they enjoy plenty of fresh air. In an overcrowded garden, airflow stagnates, just as it does in an overcrowded room. Without free air circulation, foliage dampened by dew, rain, or sprinkling will stay wet longer and be more susceptible to fungus and other diseases.

    Giving your plant plenty of room to grow will help prevent disease.
    Giving your plant plenty of room to grow will help prevent
    disease. See more pictures of garden ideas.

  • Choose disease-resistant cultivars whenever possible. They are bred to resist infection -- an ideal way to avoid diseases. Growing disease-resistant vegetables prevents chemical tainting of your food. Disease-resistant varieties of popular flowers such as roses save you time, trouble, and expense.

    There are varying levels of protection available:
    • Some cultivars have multiple disease resistances for maximum protection. The 'Big Beef' tomato, for instance, resists various types of wilts: tobacco mosaic virus, nematodes, and gray leaf spot. Little is left that can harm it.
    • Some cultivars resist only one disease. But if that disease is a problem in your area, then these plants will be worth their weight in gold.
    • Other plants are disease tolerant, meaning they may still get the disease but should grow well despite it.

To find out more about disease-resistant cultivars for your area, ask your local Cooperative Extension Service or a knowledgeable professional grower. Or get your name on the mailing list for nursery and seed catalogues that describe disease-resistant cultivars.

  • Spray plants susceptible to foliage fungus with wilt-proofing solution before disease strikes. This product is a pine oil modified to spread into a film coating that protects evergreen foliage from drying out during winter. An unexpected side effect of the film is that it keeps fungus spores from penetrating into susceptible leaves.

    Mix according to label directions and try it on phlox, bee balm, cucumbers, watermelons, tomatoes, and apples. Do not, however, spray plants with hairy leaves.

  • Experiment with baking soda sprays to prevent fungus diseases. Mix 2 teaspoons baking soda in 2 quarts of water with 1/2 teaspoon corn oil. Shake well, put in a sprayer, and go to work. Spray susceptible plants often and always after rain to help keep diseases such as powdery mildew from getting started.

  • Thin stems on disease-prone plants to improve air circulation. Mildew-susceptible phlox and bee balm, for instance, can grow into clumps so thick that they block air flow. This encourages fungus attack, but it is easily corrected. When new growth is coming up in the spring, cut out every third stem, targeting those that are weak or in areas of the thickest growth.

Pests can also be detrimental to plants. Find tips on how to prevent garden pests on the next page.

Some Disease-Resistant Cultivars
These plants have been proven to be resistant to disease:
  • Roses: 'The Fairy,' 'Red Fairy,' rugosa roses, 'Carefree Delight,' David Austin English Roses, Town and Country Roses, Meidiland roses

  • Zinnias: 'Star Gold,' 'Star Orange,' 'Star White,' 'Crystal White,' 'Cherry Pinwheel,' 'Salmon Pinwheel,' 'Rose Pinwheel,' 'Orange Pinwheel'

  • Cucumbers: 'Park's All-Season Burpless Hybrid,' 'Fancipack,' 'Homemade Pickles,' 'Tasty King,' 'Sweet Success,' 'Salad Bush'
  • Peas: 'Super Sugar Snap,' 'Sugar Pop,' 'Maestro,' 'Green Arrow'

  • Beans: 'Florence,' 'Buttercrisp,' 'Jade'

  • Tomatoes: 'Celebrity,' 'Better Boy,' 'LaRossa,' 'Enchantment,' 'Sunmaster,' 'Mountain Delight,' 'Big Beef,' 'Beefmaster,' 'Sweet Million,' 'Viva Italia,' 'Roma'
  • Apples: 'Liberty,' 'Jonafree,' 'MacFree,' 'Freedom'

  • Strawberries: 'Surecrop,' 'Cavendish,' 'Redchief,' 'Allstar,' 'Guardian,' 'Scott,' 'Lateglow,' 'Delite'

Want more gardening tips? Try:

  • Gardening Tips: Learn helpful hints for all of your gardening needs.
  • Annuals: Plant these beauties in your garden.
  • Perennials: Choose great plants that will return year after year.
  • Gardening: Discover how to garden.

Preventing Garden Pests

If your garden is filled with pests, don't just reach for the pesticide. There are other, safer, methods to use to keep garden pests at bay.

  • Interplant herbs and flowers with vegetables to help reduce pest problems. This gives the vegetable garden a colorful patchwork look and helps confuse problem pests. The varied aromas of interplantings make it hard for pests to find their favorite food by scent. This works particularly well if you interplant with powerfully fragrant herbs and flowers such as mints, basils, lemon geraniums, garlic, or onions.

  • Attract beneficial insects. Sprinkling flowering plants amid the garden helps draw ladybugs, spiders, lacewings, and tiny parasitic wasps who prey on plant-eating pests. The flowers provide shelter plus nectar and pollen, an alternative food source.

    Once beneficial insects are at home in your garden, keep them there. Remember, they can be killed as quickly as plant pests by broad-spectrum pesticides, which kill indiscriminately. It's best to avoid pesticides or use targeted pesticides such as Bt (a bacterial disease of caterpillars that won't harm other insects) to protect beneficial insects.
  • Use floating row covers to keep pests off vegetables. This simple idea works so well it's a wonder nobody thought of it years ago. Floating row covers are lightweight fabrics that you can drape over plants. They allow sun, rain, and fresh air to penetrate, but if secured to the ground with rocks, bricks, or long metal staples, they will keep flying insects out. Here are some great ways to use floating row covers:
    • Eliminate maggots (fly larvae) that will tunnel into the roots of radishes, turnips, carrots, onions, and other vegetables. Row covers keep egg-laying female flies away from the vegetables. If there are no eggs, there are no maggots.
    • Keep potato beetles from eating the foliage off potato leaves and vines. Pin the row cover edges down tightly so the beetles can't crawl under.
    • Protect cucumbers, squash, and pumpkins from cucumber beetles, which carry a wilt disease capable of killing entire vines. Since flowers of these vines need insect pollination for fruit set, the covers must be lifted for several hours at least every other day for honeybees to do their work.

  • Use barriers of copper strips or diatomaceous earth to keep slugs away from plants. Slugs are voracious plant eaters. They eat almost anything, ganging up on tender succulent plants and eating them down to the ground. They thrive where soils are damp, spending sunny days under rocks, logs, or mulch and coming out to eat when it's rainy or cool and dark. Any slug control measures you use will work better if you clear out excess mulch and any dark, dank hiding places where slugs might breed.
    • Diatomaceous earth is a gritty substance that pierces the skin of soft-bodied slugs. Sprinkle it on the soil, encircling plants plagued by slugs. Use horticultural-grade diatomaceous earth, not the kind sold in swimming pool stores.
    • Copper strips, set around the edge of the garden, prevent slug trespass by creating an unpleasant reaction when touched with the mucus on the crawling slugs. Set copper strips an inch deep and several inches high, so that slugs can't get over or under.

  • Kill existing slugs by trapping them in deep saucers of beer. Slugs love beer, and that can be their downfall. Bury an empty plastic margarine tub in the garden soil. The top rim should be level with the soil surface. Fill the tub with beer (any kind will do) and leave it overnight. The slugs will crawl in and drown. Empty the tub every day or two and refill with beer until the tub comes through the night empty.

    Use a strong spray of water to get rid of aphids.
    Use a strong spray of water to get rid of pesky aphids.

  • Spray aphids off plants with a strong stream of water. Aphids, small sap-sucking insects with soft, pear-shaped bodies, cling to succulent young stems and buds. They reproduce quickly, sometimes covering stems that curl and distort in protest. Because aphids can multiply into swarms almost overnight, it's important to eliminate any that you find.Before hauling out any pesticides, try a strong blast of water from the hose. Aphids are easily dislodged from plants. This method works best on mature or woody plants that won't be damaged by the force of the water blast. Repeat every couple of days or any time you see new aphids arriving.
  • Use bags of soap or human hair to repel deer. Sometimes called jack rabbits on hooves, deer can be a nuisance. They seem to enjoy dining on cultivated plants and are worst in the winter, gobbling evergreens when their native food supply dwindles. But they are also a problem in spring and summer, when they like to munch tender flowers and new growth. In fall, males rub their antlers on wood and can damage small trees and shrubs. However, they don't enjoy strong-smelling soaps and human hair.

    Powerfully scented soap can be stuffed in a mesh bag and dangled from branches about 3 feet high. You also can set soap bars directly on the ground. Replenish the soap supply frequently so it won't dissolve away or lose its smell.You can also fill mesh bags with human hair. Hang them outside (like a furry scarecrow) so deer wonder if you are hiding in the garden. Refill bags as soon as you pull another handful from your hairbrush.

No one wants disease or pests to ruin a beautiful garden. Be mindful of the tips outlined in this article, and you'll be more protected from these pesky outside forces.

Some Plants Preferred by Deer
Based on Cornell Cooperative Extension Service research, the following plants are attractive to deer:

Want more gardening tips? Try:

  • Gardening Tips: Learn helpful hints for all of your gardening needs.
  • Annuals: Plant these beauties in your garden.
  • Perennials: Choose great plants that will return year after year.
  • Gardening: Discover how to garden.