Deborah Raphael: Dealin with Springtime Pests

It's springtime in San Francisco and all things are made anew. There are new buds on the trees at McLaren Park and new flowers at Strybing Arboretum. Birds are building nests alongside Lake Merced and after winter's confining cold, people all over the City are itching to get outdoors.

But these warm spring days that bring new life to trees and plants ­ and waves of people to our city parks ­ also brings a new crop of milkweed, dandelions, ants and snails. That's why springtime can also be pesticide season.

The use of pesticides in public places creates potential public health risks. Children are especially vulnerable to pesticides because they can be exposed repeatedly through outdoor play and because they have small, rapidly developing bodies.

About four years ago San Francisco adopted a pest control approach that minimizes the use of toxic chemicals on city property and gets rid of pests by methods that pose a lower risk to public health.

We use corn meal mulch and torches to keep weeds down in City parks. We release mosquito-eating microorganisms in City ponds and cockroach-eating geckos at the Conservatory of Flowers. The City employs herds of weed-eating goats at Hetch Hetchy and the airport. And we have a list of 50 reduced-risk chemicals to use when creative, non-chemical solutions prove ineffective.

Since we've started using alternative pest control techniques, we've reduced overall pesticide use in city parks by more than 50 percent and have stopped using all of the most dangerous products entirely.

Measures to Reduce Pesticide Reduction at Home
Not everyone has room in the backyard for a herd of goats. And it may be a little implausible for most people to use propane-powered torches like the ones we use in Golden Gate Park. But there are many simple things anyone can do to reduce pesticide use, whether in the garden or inside the home.

Most of us have an overwhelming urge to grab a can of bug spray when we see a trail of ants in the kitchen. But spraying just leaves dead bugs to clean up and fills your kitchen with noxious fumes ­ while doing nothing to address the real problem. There's a massive colony of ants nearby with a fertile queen and hundreds of thousands of worker ants ready to make another foray.

So instead of spraying, use ant bait. Baits are better because the ants will carry the bait back to the colony and feed it to the queen and fellow workers.

Look for commercial products that use boric acid, which is deadly to ants but easy on humans. You can also make your own simple ant bait from the recipe below.

If you have a snail problem, the best solution is iron phosphate. It does the job on snails but won't harm pets the way traditional snail pellets can. We've had great success in Golden Gate Park with a product called Sluggo, which has iron phosphate as an active ingredient. All you have to do is put Sluggo in a snail trap or half-buried margarine container and the snails will come. Some people use beer to bait snail traps, but we prefer Sluggo because beer gets moldy.

To keep weeds from taking over your flowerbeds and vegetable gardens, you have many non-chemical options to choose from. One of the most effective of these is covering the open dirt between your plantings with mulch. You can use any of many natural products including small rocks, wood chips or cocoa hulls, which smell like chocolate!

Some sprouted weeds will break through the mulch, but these will be easy to pull out because the mulch weakens the weed's root systems. The mulch blocks light from reaching the soil so weaker weeds will not germinate.

You might also consider putting weed cloth beneath your topsoil as a weed buffer. Like mulch, weed cloth prevents weed seeds deep in the soil from reaching the light of day. Weed cloth comes in all shapes, sizes and materials, and can be cut to fit your flowerbeds or to go around trees and shrubs.

Ask your local nursery to help find the best product for your specific needs.

You could use cardboard in place of weed cloth, which like cloth allows water to drain through into the soil. Cardboard is quickly biodegradable, however, and will allow weeds to break through much sooner than fabric. Don't use plastic instead of cloth or cardboard because it blocks water and can suffocate the roots of the plants you're trying to protect.

City gardeners have also had good luck using corn gluten, a natural herbicide that doesn't allow seeds to germinate. Lay it thick in the areas you want weed free and work it into the soil.

Finally, if you're going to use a chemical pesticide, take a look at the warning labels and read the directions carefully. If you see "danger" on the package, you can be certain that you've picked up one that contains the most toxic chemicals available on the market. Put "danger" back on the shelf and try one labeled "caution." You'll still need to be careful using it, but the active chemicals will be less toxic ­ and chances are it will work just as well.

Recipe for Boric-Acid Ant Bait
From "Common Sense Pest Control," by William & Helga Olkowski and Sheila Daar, the recipe says:

1) Mix 3 cups of hot water with 1 cup of sugar and 4 teaspoons of boric acid or borax (available at all hardware, garden and drug stores). Don't add too much boric acid or you'll kill the ants before they reach the nest!

2) Pour small amounts of bait into plastic film containers.

3) Loosely pack cotton wool into the can, then saturate it with the bait solution.

4) Put the lid on the can, and pierce the center with two or three small holes.

5) Place the bait cans in areas where your ants will find them.

CAUTION: Label the containers with a skull and crossbones. Baited solution should be kept away from youngsters and pets.

Deborah O. Raphael coordinates the city's less-toxic pest management program at the SF Department of the Environment. To learn more about SF Environment and the city's pest management program, visit the department's website at: www.sfenvironment.com.