Here at Gardening Know How we get lots of questions, and our goal is to provide answers to those inquiries to the best of our knowledge, be it on how to grow and care for certain plants or how to treat for pests and diseases. The following information includes the 10 of the most commonly asked questions we receive about insect pest control in the garden.
To control slugs and snails in the garden, limit mulch to 3 inches or less and keep the garden free of plant debris, wooden boards, and other hiding places. If you can tolerate the “yuck” factor, put on a pair of gloves, grab a flashlight, and go slug hunting in the evening. Pick the pests off your plants and drop them in a bucket of soapy water. Tuna cans filled with beer serve as effective slug traps. Just empty the “traps” in the morning. If slugs are still a problem, try slug bait, either chemical or non-toxic. Crushed eggshells or diatomaceous earth sprinkled around plants seems to help too.
Both fall webworms and sod webworms present challenges to gardeners. The best defense for these pests is good care. Maintain your lawn, trees and shrubs properly; healthy plants are less susceptible to webworm infestations. Water and fertilize regularly (but don’t over feed). Set your mower at 3 inches and avoid “scalping” your lawn. Neem oil is an effective organic insecticide. Bacillus thuringiensis, a naturally occurring bacterium found in soil, is often effective against webworms. Chemical pesticides usually aren’t necessary and should be used sparingly and only as a last resort.
You can remove light aphid infestations with a sharp blast of water from a garden hose. Otherwise, spray the pests with commercial insecticidal soap or make your own by mixing 2 to 5 tablespoons of Castile or other natural liquid soap and 2 tablespoons of cooking oil with a gallon of water. Start with the weaker solution and increase the amount of soap only if the gentle solution is ineffective. Use caution and don’t spray when sun is directly on the leaves. Avoid spraying if you notice bees or other beneficial insects on the plant.
Controlling aphids is the first step in getting rid of ants in the garden, as the pests leave honeydew that attracts ants to your plants. If ants are still a problem, make your own bait traps. Warm ¾ cup of honey or maple syrup in the microwave for a few seconds, then stir in ¼ cup of boric acid. Place globs of the mixture on margarine container lids and distribute them around your garden. (Don’t place the bait directly on the soil; it may harm plants). Ants will carry the sweet bait back to their nest. Boric acid is toxic, so keep it out of reach of children and pets.
Keep your plants in tiptop shape by watering and fertilizing properly, as healthy plants are less susceptible to pests. Remove wilted blooms and other plant matter and keep weeds under control, then dispose of debris immediately. Avoid pesticides and use organic control, as toxic chemicals will kill friendly bugs that prey on pests. Plants such as fennel, basil, marigolds, lavender, rosemary and thyme may help repel pests, and others, like dill and parsley, can attract beneficial insects like ladybeetles and lacewings. If you have space, build a small pond in a corner of your yard to attract hungry toads and frogs.
It’s impossible to completely eliminate Japanese beetles (most birds don’t even like them!), so there are few natural controls. The best way to keep the beetles in check is to pick them off your plants by hand in the morning or late evening. Begin at the top of the plant and work your way down, then drop the pests into a bucket of soapy water. Floating row covers are a good way to protect vegetables. Alternatively, spraying your plants with neem oil or a pyrethrin-based insecticide at the first sign of trouble may help.
Whiteflies, pests that lay eggs by the hundreds on the underside of leaves, are difficult to control because they go from egg to adult in a couple of weeks. Monitor plants closely and take action as soon as you notice signs of trouble. Apply neem oil, which works by suffocating the pests, or spray affected plants with insecticidal soap, but don’t use either when the temperature is above 90 F. (32 C.). Yellow sticky traps often reduce whitefly numbers. Avoid pesticides, which kill beneficial predators such as lacewings, spiders, parasitic wasps and lady beetles.
Water well during hot, dry weather because spider mites are attracted by dust. If conditions are conducive to mites, spray foliage occasionally with a strong blast of water to dislodge the pests. Apply horticultural oil in early spring or late fall to destroy overwintering eggs. Repeat regularly if mites continue to be a problem, or spray the pests with insecticidal soap or spinosad, a product made from a natural soil bacterium. Be sure to coat the underside of leaves. Avoid chemical pesticides, which make the problem worse by killing beneficial predators. Pull weeds regularly and keep the area free of plant debris.
Neem oil can be used on pests at any stage of development, and the oil is safe to use on vegetables up to the day of harvest. The product is available in various forms, including granules, powder and wettable dust. However, the most common is a concentrate that you mix with warm water and apply with a plant sprayer. You can spray neem oil directly on leaves, but don’t apply oil when temperatures are above 90 F. (32 C.). Avoid using neem oil on wilted or stressed plants, or on sensitive plants such as fuchsia or hibiscus.
Unlike pesticides that work by poisoning pests, insecticidal soap sprays kill pests by breaking down their outer shell. In order to be effective, they must wet the insect. Also known as horticultural soap, commercial soap sprays are carefully calibrated to deliver the proper proportions and may be safer and less harsh than homemade sprays. However, homemade sprays, commonly made with liquid dish soap and water, are generally safe and effective when used properly. Some formulations include a small amount of oil, which helps the spray adhere to the leaves.
We all have questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We’re always here to help.