A Pest Management Primer - The Westside Gardener

Let's start with the obvious: Every garden contains bugs! Some of these are beneficial to the gardener, such as spiders and ladybugs. Others more or less coexist with the garden without causing much damage, such as pillbugs. Unfortunately, there are also bugs that are harmful to plants; the bad news is they undoubtedly dwell in your garden too.

People used to think in terms of eradicating pests, but now the watchword is management. This means coming to the realization that there will always be some pests present, yet keeping their numbers - and damage - at acceptable levels.

In a natural setting, and even in our gardens, a temporary excess of one type of bug often will correct itself. Either the food supply will dwindle, or a species that preys upon the pest will increase in numbers. Unfortunately, gardening is by definition inherently unnatural, since we are at least to some degree altering our environment (even a "natives only" garden uses plants that aren't naturally found in the same proximity. In any case, if I were to rely on the foodstuffs native to my area, I'd be eating a lot of nuts and berries, and catching fish. A decent diet, but not really practical anymore). In addition, many of the worst pests are introduced species, and enjoy freedom from natural enemies in their adopted home. So sometimes we have to step in and deal with the pests ourselves.

Weeding regularly and cleaning up plant litter helps minimize the hiding places available to the pests. Adding organic matter to your soil keeps it loose, allowing predators such as beetles and centipedes easier movement through the soil. Crop rotations help keep pest populations from growing too large in one area of your garden. Remember that common sense will go a long way towards helping keep pests in check. For example, if you live in slug heaven, don't put mulch around the plants they love to eat!

Here are the steps I try to follow with regard to pest management:

Step 1: Evaluate the situation. Are we just talking about a few holes in the lettuce, or are entire rows of plants being mowed to the ground? If the damage is not severe, just live with it! The occasional spinach leaf may be a bit chewed, but it still tastes as good! This may take a mental adjustment on your part, but consider this: Would you rather have shared part of your salad with a bug, or eat perfect-looking leaves that have been drenched with pesticide?

Step 2: Figure out what the pest is, and if it is actually causing damage. This may seem obvious; but identifying the problem goes a long way towards determining the solution. Also, you may find out that the "pest" you thought you'd identified is actually beneficial to the garden! I know people who absolutely detest centipedes, and are surprised to find out that these fast little creatures are some of the better predators in the garden. Just because you aren't certain what a bug is, don't assume it is bad!

Step 3: Check to see if countermeasures are already being taken. Often a "bloom" of bad bugs will be followed by a "bloom" of good bugs. For example, if your broccoli is covered with aphids, check to see if ladybugs or their larvae are present. A single ladybug (adult or juvenile) can eat scores of aphids in a single day! Parasitic wasps will use caterpillars as walking nurseries, laying eggs in the still-alive host. Some people encourage these parasitic bugs by letting various plants (such as dill) go to flower in their garden; these attract adult bugs, which lay eggs (often the parasitic form of a bug is in its juvenile stage of development - does that sound familiar to any parents of teenagers?).

Step 4: Determine if a barrier or trap will solve the problem. In my immediate area, there are commercial cabbage growers. One result of this is that cabbage pests, such as the cabbage maggot and imported cabbageworm, sometimes seem ubiquitous. Now I COULD poison the soil to kill the maggots, and I COULD cover the leaves with pesticides; but I know that both these pests are larvae of flying parents - the cabbage maggot fly and the cabbage white butterfly, respectively. This means that I can keep my cabbage-family crops pest free by growing them under a floating row cover.

Step 5: When necessary, use the least toxic effective means of control. Some examples: Slugs and caterpillars can be picked up by hand, and dropped into a bucket of soapy water. Small caterpillars can be controlled with a spray of Bt, a bacterium that is poisonous to caterpillars (technically it is parasitic, but some byproducts of its reproduction are poisonous) but harmless to other creatures. Aphids can be hosed off the plant with water, and will not usually climb back on; just be sure the force of the spray doesn't damage the plant. Since bugs breathe through spiracles (openings) on their bodies, spraying them with Safer's Soap will often kill them (use a soap, like Safer's, that is marketed for insecticidal purposes. Some other types of soaps can harm plants.). If you feel you must use a poison, use a botanical such as Rotenone or Pyrethrum. Synthetic pesticides persist in the environment, and on your vegetables; botanicals will break down in the environment. Remember that these can still be toxic to mammals, and even people, if not used carefully. ALWAYS follow the directions when using a poison, and NEVER use them on a plant for which they are not specifically approved.

Step 6: ONLY INTERVENE WHEN NECESSARY. Even when using organic or botanical pesticides, it is best to use them minimally. Botanicals and organics may not persist in the environment the way synthetic chemicals do, but using them repeatedly over time mimics the same sort of persistence. There have been at least two documented cases where moth larvae have become resistant to Bt, mainly due to organic commercial farms spraying it on a regular schedule. Spray ONLY the affected plants, not everything in the garden. Remember that even organic controls can harm beneficial insects if not used carefully.