Your garden is an ecosystem thriving with life - it is home to innumerable microorganisms and hundreds of insects as well as birds, mammals, amphibians - and humans, too! Teach children to welcome biodiversity in the garden, and to distinguish between harmful and beneficial insects. From the start, follow safe practices in pest prevention, such as:
- Buying healthy plants
- Maintaining healthy soil to keep plants strong
- Rotating crops from season to season
- Growing plants that attract beneficial insects (such as ladybugs, lacewings and spiders) who will consume harmful insects before they consume your crops!
Below is a list of harmful insects commonly found in gardens, as well as recommendations for natural pest controls.
Aphids are 1/32"-1/8" in size. Most commonly seen in clusters on the undersides of leaves, aphids feed on many garden vegetables, fruit trees, and ornamental plants. In low numbers, they are not harmful, but many of them can cause stunted plant growth, and some can even transmit plant diseases. To control, prune heavily infested leaves and hose off plants with a strong stream of water. Attract natural predators, such as ladybugs and lacewings, whose larvae eat aphids. Plant members of the daisy family, or yarrow to attract ladybugs. Attract lacewings with yarrow, goldenrod, black-eyed susans, and asters. You can also smother aphids with a solution of one tablespoon canola oil and a few drops of dish soap in a quart of water. Put the solution in a spray bottle, shake well, and shoot plant with sprays of solution from above and below.
This pest chews large holes in the leaves of cabbage and related plants like broccoli, cauliflower, kale, and turnips. It may also bore into the center of these crops and contaminate them with its fecal matter. It is considered extremely destructive.There are many natural predators of the cabbageworm, including spiders, yellow jackets, lacewings and parasitic wasps, so attract these beneficials. However, this pest often requires even more rigorous attention. As soon as damage is noticed on leaves, begin handpicking the worms from the plants. After harvest, till under the garden debris to kill overwintering pupae before the adults emerge.
Colorado Potato Beetle
These insects are problematic throughout the United States; both the adults and the larvae can completely defoliate an entire crop. Alternate host plants include tomatoes, peppers, and eggplants. As soon as plants emerge, mulch at least 2-3 inches deep with a layer of hay to impede the movement of overwintering adults. You can also protect plants with floating row covers through spring, and attract predators like ladybugs and lacewings. Another method: in early morning, shake adults from plants onto a ground cloth and then dump into soapy water.
1-2" caterpillars with shiny heads, these insects do most of their damage at night, when they feed by clipping off seedling stems and young plants near or just below the surface of the soil. They attack a wide variety of plants, most commonly beets, cabbage, broccoli, kale, and cauliflower. Before planting a new garden, first remove weeds and plant debris so that the developing larvae have nothing to eat (note: the larvae themselves do not harm plants). When planting your transplants, place cardboard collars (this can be a toilet paper tube) around the stems. Also, like slugs, cutworms cannot tolerate rough surfaces so coffee grounds, eggshells, or diatomaceous earth around plants can help deter them. Finally, after harvest, pick up garden debris and turn over the soil around plants to disturb overwintering larvae. .
Earwigs can be beneficial because they eat organic debris like dead leaves, and socan be helpful near a compost pile. However, they can also attack young plants like carrot tops and dill. One solution is to grow these vegetables earlier in the season so that they are hardier by the time the earwigs mature. Gardeners can also set out bait like molasses or soy sauce with water, or peanut butter in a small container. Periodically collect the bugs and tap them into a pail of water.
Mexican Bean Beetle
Both the adult and the larvae feed on the undersides of leaves, and can attack young pods and stems. Damage occurs on all bean varieties, including bush, pole, lima, pinto, navy, kidney, and soybeans. Damage is most severe in summer months, so consider planting early-maturing bean varieties. Adults and larvae both can be handpicked from plants and dropped in pails of soapy water; be sure to remove bright yellow eggs from the undersides of leaves. Beneficial insects such as ladybugs and lacewings prey on both the egg and young larval stage. Floating row covers can be used as a physical barrier to keep beetles and larvae from damaging plants, or diatomaceous earth can be used to deter larvae.
Appearing most frequently during particularly wet periods, slugs will eat a broad range of crops including root vegetables and fruit, but almost all crops are subject to attack. Slugs are particulatrly harmful because they can eat a plant faster than it can grow. Even on root vegetables whose leaves are less valuable, slugs can kill the plant by removing its ability to photosynthesize. Placing a ring of coarse material such as crushed eggshells or coffee grounds around plants deters slugs; their soft undersides cannot tolerate these barriers. You may also try using diatomaceous earth, which is the crumbled, fossilized remains of diatoms, a type of hard-shelled algae.
Tomato hornworms consume leaves, stems, and fruit, and are particularly destructive pests of tomatoes, potatoes, peppers, and eggplant. Because they are so large, they can somewhat easily be controlled by handpicking, followed by immersion in a bucket of soapy water. Roto-tilling after harvest destroys overwintering pupae in the soil. Also plant crops that attract insects who feast on tomato hornworms: plant members of the daisy family or yarrow to attract ladybugs. Plant yarrow, goldenrod, black-eyed susans, and asters to attract lacwings.
Harmful Bugs Illustrated Chart!