Do you hate bugs? You’re not alone. Most of us recall feeling similarly before we started working the earth; our outlook changed after learning, firsthand, how beneficial insects can be to our gardening efforts. For example, lady bugs, ground beetles, lacewings, damsel bugs, and tachinid flies are a few examples of insects who provide benefit in the garden by preying on parasitic insect pests. Opposite of the “good” bugs, garden insect pests such as leafminers, spider mites, mealybugs, and slugs and snails can wreak havoc in the garden in a matter of days in their relentless quest for nourishment which they typically get by sucking the juices out of plant leaves.
In a perfect, balanced world, the good garden bugs keep the bad garden bugs in check. The problem is, in their haste to eradicate pests at the first sign of a problem, many people turn to man-made chemical insecticides for a quick fix. Unfortunately, these insecticides only exacerbate the problem over the long run: the pesticides kill off the beneficial insects while the garden pests remain, quickly developing resistance to the chemicals. The pests’ numbers quickly multiply in the absence of predators and they become an infestation causing major damage to our plants. It makes much more sense to figure out ways to deal with garden pests using safe, non-toxic, “natural” methods which will be sustainable over the long run.
Preventing Garden Pests from Taking Over
That old saw, “An ounce of prevention is worth a pound of cure” is apt for dealing with garden insect pests. Starting with rich, well drained soil, enhanced, if necessary, with organic compost will help ensure strong, healthy plants with a greater ability to fend off predators than weak ones. Regular application of organic fertilizer and deep watering will also contribute to plant health. Companion planting, rotating “crops” and regular weeding will also help keep pests at bay.
“Natural” Pesticides and Repellents
Many people choose to procure or create their own “natural” pesticides and repellents without using harsh chemicals including the following:
Garlic or chile pepper spray (repellents)
Other “home” remedies such as milky spore and diatomaceous earth.
Unfortunately, many “natural” pesticides have limited effectiveness and can leave harmful residue on garden crops, and harm beneficial insects; they should be used sparingly.
Beneficial Garden Insects
Otherwise, you can resort to biological methods to reduce the threat of pests, by populating your garden with the aforementioned beneficial insects. You can either attract these good bugs by growing their favorite plants, or buy them from a commercial provider and release them into the garden.
Following is a sampling of common garden insect pests and some effective ways to get rid of them. You may encounter different types of pests, depending on the region in which you live. We will address additional common garden pests in future posts as part of a series. As always, we recommend contacting your local county extension cooperative for additional information.
Common Garden Insect Pests
Mealy Bugs - Related to scale insects, these are small, soft-bodied wingless insects which appear as white cottony masses on plants in warmer climates. In large numbers they can weaken plants by leaving a sticky residue, called Honeydew, making them vulnerable to sooty mold fungus.
Symptoms: They can cause leaves to turn yellow and fall off prematurely.
Susceptible Plants: Citrus and ornamental plants such as begonia and coleus.
How to Control:
Keep your plants healthy through regular fertilization and watering.
Blast them with a spray of water from the garden hose with a sprayer attachment
All-in-one “kitchen insect spray”
Spider Mites - A common threat to both indoor and outdoor plants, this member of the arachnid family can cause substantial destruction in a short period of time by sucking the fluids out of plant leaves. This pest overwinters as eggs in the leaves and bark of host plants and molts and proliferates in hot, dry conditions. They are easily transported by the wind, quickly expanding their area of infestation unless you stop them.
Symptoms: You can barely see these tiny pests and probably won’t notice visible damage until there’s a large infestation. At first, the leaves will show tiny spots and then may turn yellow, curl and fall off. If you look closely, you can see their tight webs formed under leaves and along stems.
Susceptible Plants: Squash, melons, sugar peas and beans and various ornamentals.
How to Control: Chemical pesticides are counterproductive because they actually encourage the spread of these pests by killing off beneficial insects that prey on them. Moreover, it has been found that these pests quickly develop resistance. Here are some better suggestions:
Stressed plants are more susceptible to pest infestation: be sure your plants are well-fertilized and well-watered.
Prune leaves, stems and other infested parts of plants (including whole plants, if necessary) and discard in trash - not compost pile.
Blast the plants with water from the hose, using a sprayer attachment. You should do this regularly throughout the season to prevent them from laying eggs and establishing colonies.
Use Insecticidal soap to spot treat heavy infestations
Obtain and release beneficial insects in the garden to prey on the mites.
Keep a close eye out for repeat infestations during warm weather
Leafminers - Larvae, appearing as small raised spots, deposited by various flies, moths, beetles and sawflies on the undersides of plant leaves which, upon hatching, “create mines” between the upper and lower surfaces in the process of sucking the fluid out of the leaves. This activity mars the plant’s appearance and can restrict growth. Mature larvae overwinter in the soil under host plants and mature through various lifecycle stages as the weather warms up in the spring. Several generations are produced each year.
Symptoms: Winding tunnel patterns appear on the leaves which rarely out-and-out destroys most plants, but leave some vegetable crops desiccated, robbing them of much of their appeal and nutritional value.
Susceptible Plants: Unfortunately, leafminers attack many different types of plants, including fruits, vegetables, flowers, trees and shrubs. They are particularly destructive to susceptible leafy greens such as swiss chard and spinach.
How to Control: This is a tough one since the leaf miners are protected by the plant leaves for most of their life. Prevention is your best bet through the use of floating row covers, secured to the ground so no adults can get at the plants to lay their eggs. Otherwise, you can do the following:
As always, healthy vigorous plants are better equipped to keep pests at bay. Keep your plants well fertilized and well watered throughout the season.
Keep a close eye on your plants: at the first sign of tunneling, use your fingers to squeeze the tunnels in order to crush the larvae. If you are vigilant and do this regularly, you may be able to keep the infestation under control.
Pick off and discard heavily damaged/infested leaves.
Cover soil under infested plants with plastic mulch to prevent larvae from reaching the ground and reproducing.
Slugs and Snails - Gardeners who live in a moist climate or have a moist shady section of the garden are probably well familiar with these destructive creatures. They have voracious appetites, are not picky eaters and leave a trail of slime in their wake of nightly destruction.
Symptoms: Leaves that are torn and have gaping holes. Slime trails.
Susceptible Plants: Most everything in the garden.
How to Control - Commercial pesticides while widely available, can be toxic to birds, other wildlife and family pets; non-toxic methods are preferable of which there are many. For example, beer traps and grapefruit traps work well, as does diatomaceous earth. Preventative measures such as watering early in the day leaving the garden relatively dry at night when they do their foraging will discourage them.
When pests attack your plants it can be really distressing to see all your hard work go down the drain. But you can keep them in check with some preventative maintenance along with careful, consistent monitoring of your plants and early intervention with non-toxic remedies. Stay tuned for Part Two in the series.