Warming spring weather means one thing: Pests and diseases are coming out in force, ready to attack tender new foliage and flowers. Before you get mad and reach for a chemical arsenal to do away with the nuisances, consider this: A cautious approach makes sense for the overall health of your garden, not to mention the children and pets who play there. Check the plants' growing conditions ― healthy, vigorous plants are better equipped to resist pests and diseases.
• Is the affected plant growing in the conditions it requires? Make sure it has plenty of room to grow, the correct amount of light (sun or shade), and sufficient air circulation around it.
• Is the soil healthy? Flowers and vegetables thrive in well-amended soil with plenty of compost. Trees and shrubs don't need soil amendments, but covering the soil around them with an organic mulch such as bark chips helps keep the roots cool and encourages beneficial organisms in the soil.
• Does the plant receive the amount of water and nutrients it needs? Water-stressed plants are weak and susceptible to attack. Water early in the morning when the temperature is rising. If good care isn't enough to keep insects or diseases at bay, identify the problem then choose the correct control method from the chart below. Give the control a chance to work before trying something stronger.
Have you seen beneficial insects in your garden?
Ladybugs, green lacewings, and other "good" bugs can keep aphids, scales, and other "bad" bugs in check. Encourage them to stay in the garden by setting out plants to feed and shelter them.
Mix annuals and perennials that bloom over a long season. Favorites of beneficial insects include coreopsis, corn cockle, cosmos, sweet alyssum, and yarrow. Avoid indiscriminate spraying, which kills good bugs too.
One way to be certain that beneficial insects inhabit your garden is to introduce them yourself. You can order them by mail or on-line from the following sources.
Harmony Farm Supply, 3244 Hwy.116 North, Sebastopol, CA 95472; (707) 823-9125.
Natural Pest Controls, 8864 Little Creek Dr., Orangevale, CA 95662; (916) 726-0855.
Peaceful Valley Farm Supply, Box 2209, Grass Valley, CA 95945; (888) 784-1722.
Aphids, Mites, Scales, and Whiteflies
Commercial product: Insecticidal soap spray (such as Safer), or horticultural oil
Home remedy: Homemade soap spray (add ½ teaspoon mild dish soap and 1 teaspoon cooking oil to a 1-quart sprayer filled with water)
Slugs and snails
Commercial product: Iron phosphate (Sluggo, Escar-Go!, Worry Free Slug and Snail), copper barrier
Home remedy: Handpick at night. Apply coarse sand.
Commercial product: Citrus spray (Orange Guard, Bugs 'R' Gone), boric acid baits, sticky barrier (Tanglefoot)
Home remedy: Caulk entry cracks. Wipe up trails with soap and water
Powdery mildews, blackspot, and rusts
Commercial product: Lime sulfur (calcium polysulfide); effective against powdery mildews and rusts
Home remedy: Baking soda spray (mix 1 teaspoon baking soda and 1 teaspoon horticultural oil in 1 gallon of water); effective against blackspot and powdery mildews