A gentler approach to pests

A garden is a complicated system that consists of soil, plants and an assortment of creatures. When the system is working correctly, little human intervention is needed to keep the landscape attractive and productive.

Each spring, though, when new growth and flower buds emerge, the appearance of certain pests can throw even the best gardeners into a tizzy. Aphids on succulent rosebuds and powdery mildew on tender young foliage are typical springtime spoilers.

Your first reaction to such invaders might be to spray (or, as some would say, “nuke ‘em”), but a wiser stance might be to do nothing. Natural enemies, which far outnumber the pests in any garden, will come to the fore -- but only if you let them. Your job is to tempt the beneficial -- or “good” -- bugs with an array of flowers and to protect them from harmful pesticides that can knock the system out of balance.

When you first notice garden pests, often the best way to lower their populations is to apply a sharp stream of water. Little insects and mites, knocked from foliage to the ground, won’t climb back up. Colonies of powdery mildew, a fungal disease, dwindle after a high-pressure shower.

Should pests threaten your harvest or a plant’s survival, and you decide that pesticides are in order, avoid broad-spectrum chemicals. Look for less toxic, lower-risk products that target specific pests. You’ll find many alternatives at your garden center.

Insecticidal soap, a staple of organic gardeners, is less toxic than table salt. But, used correctly, it tackles aphids, thrips, mealybugs, spider mites and small caterpillars.

Different strains of a parasitic bacterium called “B.t.” or Bacillus thuringiensis, are widely used to specifically control caterpillars, mosquitoes and other insects.

Time-tested materials, including horticultural oil and sulfur, are on every nursery shelf. Horticultural oil smothers insects, mites and their eggs. As a dust or spray, sulfur controls soft-bodied insects and mites, as well as powdery mildew, rust and other fungus diseases. (Note that rust is not diminished by blasting affected leaves with water; in fact, that will spread the spores.)

A new generation of vegetable-based pesticides is on the market. Orange and lemon oils are used for ants, fleas and other insects; mint oils are recommended for flying insects. Capsaicin, which gives hot peppers their fire, is lethal to many bugs. Neem-based preparations, derived from a tropical tree, provide insect and disease control. A new ready-to-use spray for powdery mildew contains jojoba oil. Pre-emergent herbicides with corn gluten stop weeds from developing.

Garlic extracts, which repel rather than kill, are odorless to humans but not to plant-feeding insects. Avoid using garlic products at pollination time, as bees will also steer clear of treated plants.

Because most “gentler” pesticides work only on contact and lose effectiveness rapidly, they must be applied more often than nastier chemicals. This translates to more work for the gardener -- a fair trade, considering the benefits.

Pesticide risk is related to dose and exposure. Before buying and using any pesticide, read the label carefully (certain products cannot be used on edibles), and follow the directions precisely.

Some organic pesticides are actually quite poisonous, and even the least toxic substances can harm the user or damage plants if handled improperly.

Wear protective clothing, as advised, and always use a mask when applying dusts or fine-particle materials such as diatomaceous earth. The package label also tells you how to store and dispose of your pesticide.

And remember: All pesticides should be kept out of the reach of children.