There are a variety of non-chemical and non-toxic alternatives to pesticides.
General Gardening Information
Avoid using herbicides in your garden and landscape. Contain weedy ornamental plants by placing them in pots in the ground. Narrow the spacing between plants in your garden to deprive weeds of light, nutrients, and water. Maintain mulch at a depth of two to four inches. Landscape fabric can also be used to control weeds.
Prevention is a key component in pest management. Proper sanitation will help reduce your need for chemical pesticides and save extra work next year. Clean up debris in your garden and around trees. Many pests and diseases overwinter in leaves, twigs, and fruits that have fallen in the litter layer.
Water plants deeply and infrequently. Check to see that your soil is moistened to a depth of 8-10 inches. Drought stress makes plants more susceptible to insect and disease damage. Water lawns and gardens (if necessary) early in the morning. Never water at night! Evening applications can lead to fungal diseases.
Reduce water usage on your lawn in hot, humid weather. Your grass will go dormant if allowed to dry out and will escape diseases that are common during summer months. Remember to mow high to choke out weeds and let clippings fly to recycle nutrients and reduce the need for fertilizer. Underfeed rather than overfeed; too much fertilizer leads to disease, thatch, and other pest problems. Also, grasscyclers are already recycling a substantial amount of nutrients every time they mow. For more information, visit our Grassycling page.
Companion plants in your flower and vegetable garden will attract beneficial and predatory insects to your plants—while repelling unwanted garden thugs. For example, marigolds repel nematodes; mints (potted to prevent overgrowth) repel cabbage pests and aphids; rue deters Japanese beetles; sweet basil controls tomato hornworm, repels aphids, mosquitoes, mites and acts as a natural fungicide and slows the growth of milkweed bugs (and don't forget pesto!); tansy used as a green mulch can repel cucumber beetles, Japanese beetles, ants, squash bugs. Chrysanthemums, chives, onions and garlic repel many pests, so plant them near your vegetable crops.
Crop rotation is a well-known practice for large agricultural operations. Why not use rotation in smaller garden situations? Move growing beds to different sections of your garden, so plants can tap new resources in fresh soil. The availability of nutrients in soil is affected by what is growing in it. Different plants use different nutrients and at differing rates, hence, rotating beds may help you reduce the need for fertilization. Allowing time for soil to rest promotes important qualities in your soil such as good aeration, drainage, and nutrient availability. Pests and diseases are also less likely to become a recurring problem when you rotate beds. Insects and disease spores often overwinter in the soil; removing the host plant from the area is sometimes all it takes to rid yourself of an irritating problem. If your space is limited, rotate plants within each bed every season. If you plant the same flowers and vegetables every year, plant them in different areas each season to reduce pest and disease problems and reduce the need for fertilizer applications.
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Bacillus thuringiensis (Bt) is a naturally occurring soil-borne bacteria which controls caterpillars. Toxins created by Bt paralyze the digestive tract of caterpillars causing them to cease feeding and die. Bt isn't hazardous to humans or other non-target animals and can be used right up to harvest time.
Made from the finely ground fossils of prehistoric fresh water diatoms. Diatomaceous Earth (D.E.) kills common household and garden pests like roaches, ants, fleas, beetles and other listed insects. For more information, visit our fact sheet: An Ancient Solution to Modern Pest Problems (PDF, 2 pp, 245K)
Horticultural oil, an effective alternative to harsh chemical pesticides, has many advantages over conventional pesticides. It acts as a smothering agent so pest resistance is unlikely to develop. Oil is less harmful to beneficial insects and predatory mites due to its low residual activity. Pesticides with a long residual can kill natural enemies for many days or weeks when they contact treated surfaces. Oil kills all stages of mites and scale insects whereas chemical pesticides often require repeat applications to control offspring from eggs and adults not affected by the chemical. Applying oil is easier and safer than spraying conventional pesticides. Avoid spraying oils when plants are weakened, stressed, or wilted. Never spray if humidity and temperatures are high or if long periods of rain are forecast. Apply oil thoroughly to get complete coverage of infested plants.
Horticultural oil is often applied in late winter to control insects like scale, mites, and aphids, however, it is better to wait until the pests have hatched in the spring because they are more vulnerable. In addition, you may eliminate overwintering predatory mites, lacewings, and other beneficial insects if you spray all of your plants with oil in the dormant season. Like any pesticide, horticultural oil should only be used when pests are evident and noticeable damage to the plants they are attacking is likely.
Are you looking for an insecticide or fungicide that is effective but won't harm your children or beneficial insects? Neem oil might be the answer. It is an organic control for many pests and is extracted from crushed kernels of the neem tree. Neem oil is biodegradable with very low toxicity. It is both a repellant and contact killer. Insects that don't feed on treated plant foliage are unharmed, therefore, neem doesn't interfere with the natural balance of the ecosystem. It acts as an insect growth regulator that disrupts the molting process. Neem can be used to control aphids, bagworms, borers, caterpillars, leafminers, lace bugs, thrips, psyllids, mealybugs, and many other insects. Neem prevents mildews, rusts, leaf spots, botrytis, scab, and other fungal diseases as well.
Recently, fungicides made with neem oil have become available commercially. Neem oil appears to have better fungicidal properties than many of the oils described above, as well as other natural pesticides. A neem-oil formulation called Trilogy has been approved by the EPA for use on foods, while Rose Defense and Triact (for control of powdery mildew, rust, black spot, Botrytis, downy mildew, and other common diseases) are designed for use on ornamentals. Make sure you buy neem with fungicidal rather than insecticidal properties.
Milky Spore is a naturally occurring bacterium that affects Japanese beetles at the grub stage of life. Milky Spore was first developed by the USDA in the 1930s to combat the Japanese beetle but Milky Spore controls the June bug and Oriental beetles as well. When grubs are feeding, they ingest the bacteria. The bacteria begins to multiply inside the gut of the grub killing it in about 14 days. Once the grub begins to decompose, billions of new bacteria are released into the soil. Milky Spore begins working upon application wherever grubs are feeding. Warm climates can achieve complete control in 2 to 3 years. Colder climates may require 3 to 5 years. Once established in your lawn, Milky Spore can last 15 to 20 years. Fertilizers and herbicides will not affect the Spore. Chemical grub controls do not harm the bacteria; however, the use of chemical controls will slow the rate of spread of the bacteria. The use of chemical grub controls along with Milky spore can be effective, but only spot spray with chemical control.
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Instead of purchasing beneficial insects, conserve those that nature sends your way. Spray pesticides only when it is absolutely necessary, and treat only the plants that are being attacked by pests or diseases. Whenever possible, use a reduced-risk pesticide such as horticultural oil, insecticidal soap, or neem seed extract to combat pests and diseases. These pesticides have minimal impact on beneficial insects. Look for insect predators when you note a burgeoning insect problem; they may be working to bring it under control for you.
You can avoid using pesticides that harm beneficial insects by exploring other control options. Physically remove pest insects from their host plants with a jet of water from your garden hose, or hand pick them into a bucket of soapy water. Be sure that you are providing your landscape plants with the conditions they need to thrive; healthy plants are less likely to be subject to pest and disease problems. When shopping for new plants, be sure to select pest and disease resistant varieties whenever you can.
You can reduce the need for insecticides in your landscape by using "insectory" plants that attract beneficial insects. Ladybird beetles, hover flies, lacewings, spiders, and parasitic wasps are natural enemies of plant damaging insects like aphids, mites, whitefly, scale, and thrips.
||ladybird beetles, wasps, hover flies
||lacewings, hover flies, braconid wasps, spiders
||lacewings, ladybird beetles, hover flies, spiders
||lacewings, ladybird beetles, hover flies, braconid wasps
|Queen Anne's lace
||lacewings, ladybird beetles, hover flies, spiders
||hover flies, spiders
||hover flies, braconid wasps
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Physical control of pests is simple and highly effective. Damage to your plants is stopped in its tracks and it takes less time than applying a pesticide. Simply remove pests from plants as soon as you spot them. Small insects such as aphids and mites can be removed with a thorough washing down of the infested plant with your garden hose. Other pests can be picked off or tapped into a bucket of soapy water.
Mites & Mealybugs
Remove spider mites and mealybugs from your plants by blasting them with water from the hose.
Gypsy moths are on the increase in many parts of the country. Apply a sticky barrier around the trunks of trees to intercept them before they eat the leaves. Hatchling caterpillars that originate from eggs on other trees and vegetation in the area will get stuck in the barrier and die. Apply wide masking tape around the tree and then apply sticky barrier material, available at garden centers and hardware stores, on the surface of the tape. Be sure to apply the tape so it conforms to crevices in the bark-if it is stretched across the bark crevices, the caterpillars may be able to crawl under it and past the barrier. You can trap the caterpillars that originate from eggs laid on the tree by tying a swath of burlap above the sticky barrier. Caterpillars seek the shelter of the burlap during the daylight hours. Check under the burlap daily and destroy any caterpillars that you find by dropping them into soapy water. Remove the sticky barrier and the burlap before the end of August.
Watch out for conical masses of plant material hanging from branches or leaves on your conifers or deciduous trees and shrubs. These are the work of a pest called the bagworm. They are native to North America and feed on many different plants. Bagworms spend their lives in a cocoon-like case made of silk, bits of twigs, and leaves. Eggs hatch in late May or early June. Small larvae feed on the upper side of the leaves and older larvae move to the underside. The whole leaf is eaten except for the major veins. By mid or late August, the caterpillars begin to pupate in their bags. Hand picking is an inexpensive control measure. Bacillus thuringiensis (Bt) will control bagworms early in their larval development.
Willow Leaf Beetle
Watch out for greenish blue to shiny black beetles chewing on your willows and poplars. The adult willow leaf beetle begins feeding on leaves as they emerge in early spring and chew holes in the foliage. Eggs are yellowish, cylindrical, and are found in irregular masses on the underside of leaves. The small black larvae cause the most damage by chomping on the underside of leaves, exposing leaf veins. Air pollution studies suggest that leaves exposed to excessive ozone are preferred by the beetles. Ladybird beetles, lacewings, predacious bugs, spiders, and a wasp that kills the pupae help control the willow leaf beetle. Protect these beneficials by avoiding insecticide use and providing suitable overwintering sites.
Hemlock Woolly Adelgids
Look for hemlock woolly adelgids (PDF, 2 pp, 166K) on the underside of the lower branches of your hemlocks. Adelgids secrete masses of white, fluffy protective wax that make them easy to spot. Heavily infested branches are stunted and may lose their needles; damage may result in death if left uncontrolled. The vulnerable stage of the woolly adelgid is the crawler stage. Crawlers are small, brown, and oval and hatch in early spring. They migrate to the new growth where they may be found at the base of the needles. Tap infested branches over a white piece of paper to determine if crawlers are present. Wait to treat hemlocks until the crawlers have hatched and spray them thoroughly with horticultural oil. Don't fertilize hemlocks with woolly adelgids since extra nitrogen increases the adelgid's rate of reproduction.
To keep cutworms away from vegetable plants, remove both ends from a can and sink the "collar" around the base of plants.
Eastern Tent Caterpillars
Look for eastern tent caterpillar egg masses on your wild cherry, crabapple, and apple trees. The black egg masses surround the twigs and are less than an inch long. Prune the egg masses out or scrape them off the branches. If you don't have a chance to remove them, look for silken nests in the branch forks when buds begin to break dormancy. Remove the nests to prevent defoliation.
Check plants for silvery slime residue and look for irregularly shaped holes with tattered edges in the leaves. To help prevent problems, don't mulch around hostas and other plants that slugs prefer. Use copper flashing to encircle valuable plants. Place a saucer of beer or yeast solution (add a cup water to a teaspoon of yeast) flush with the soil surface in your garden. Change the solution every two days and remove any slugs you find. Continue to use the traps until you no longer find any slugs in the saucer.
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Garden Plant Diseases
Protect Trees from Disease
One of the most common causes for disease in trees is damage to bark and roots
from lawnmowers and weed-whackers. Nicking the bark or striking
exposed roots can create wounds, allowing infection from disease
pathogens, fungi, and insects. Protect your trees by creating a
buffer zone of mulch at least two feet out from the trunk, but not
up against the trunk, and as far out as the tree's drip line. Apply
mulch two-three inches thick. The mulch will protect against physical
damage, reduce competition from weeds and grass, conserve moisture,
and eventually breakdown and release nutrients.
Garlic for the garden
You can use garlic to control some of the most common plant diseases like black spot, mildew, rust, blight, and fruit rot. First, mix two bulbs of garlic in your blender with four cups of water and several drops of liquid dishwashing soap. Blend thoroughly and filter through cheesecloth. Keep the mixture refrigerated. Apply directly with brush or sprayer for serious infestations; dilute one part garlic mixture to nine parts water for a overall preventative spray for powdery mildew. Use every week or two.
Hold a Compost Tea Party!
Mix one part finished compost with six parts of water and let the mixture soak for a week. Filter off solids with cheesecloth. Dilute liquid until it has a tea-like color. Compost tea is effective in controlling powdery mildew and Botrytis gray mold. Apply every 14 days. Spray small area first to check for plant damage. Repeat with each new batch.
Powdery Mildew on Roses
To control powdery mildew on roses: spray both sides of rose leaves with: 2
tbl mild liquid soap, 2/3 tsp baking soda in 1 gal water. Spray
in the morning, weekly. Spray leaves at the first sign of powdery
mildew with an antitranspirant (e.g. Wilt-Pruf) as a preventative.
Worst-case scenario: use sulfur-based fungicides, the least toxic
of the conventional fungicides. Please note: sulfur-based fungicides
generally have low toxicity to humans, but sulfur has been known
to cause a skin rash when used by persons wearing short-sleeves
in hot weather.
Powdery Mildew on Dogwoods
Watch for powdery mildew on your dogwoods. It is a serious disease
that stunts new growth and stops growth entirely if severe. Unlike
most fungi, powdery mildew does not require water on the leaf surface
for spore germination, so it will invade even in dry weather. Neem-based
pesticides or horticultural oil will cure the problem.
Check your dogwoods for straight, succulent suckers and watersprouts that may be growing from the trunk and large branches. Although this growth may appear to be vigorous and healthy, it makes dogwoods more vulnerable to dogwood anthracnose. This fungus disease causes tan spots with purple borders to appear on the leaves in spring. Dogwood anthracnose only becomes deadly when the fungus grows into the trunk or large branches and kills the living tissue called the cambium layer underneath the bark. Remove suckers and watersprouts to deprive the fungus of its most direct route to the vulnerable cambium.
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Kill weeds in driveways, sidewalk cracks, and similar areas with boiling water instead of herbicides or other chemical remedies. It's safer, cheaper, and works quite effectively.
Vinaigrette for Weeds
A safe, biodegradable herbicide can be created by blending vinegar and lemon
juice. The resulting mix provides non-selective control of herbaceous
broadleaf and grass weeds, including chickweed, ragweed, plantain,
crab grass, quack grass, and wild carrot. Results can be seen in
as little as two hours. You can make your own by filling a spray
bottle with a mixture of 1 cup vinegar and 1/4 cup lemon juice.
Spray directly on the weed—and ONLY on the desired (or undesirable)
weed—when the sun is out. These simple, homemade blends may
require you to spray a weed two or three different times, but the
tangy mix will get the job done. For immediate results, consider
using a commercial product; they are stronger and faster-acting.
Several blends are sold under the following trade names: Nature's
Glory Weed and Grass Killer and Burnout.
Corn Gluten has been proven effective against most common garden
and lawn weeds. It's safe for people, pets, fish, and wildlife because
its made entirely from one of nature's most wholesome grains—Corn
Various manufacturers produce corn gluten-based weed killers, some
of which have added natural nitrogen to serve as a fertilizer or
organic "weed and feed" product. Corn gluten itself contains
10% nitrogen by analysis. All products work as a pre-emergent weed
killer, preventing weed roots from developing so new seedlings quickly
die. Most are effective against dandelions, crabgrass, clover, giant
foxtail, creeping bentgrass, barnyard grass, and most other
garden and lawn weeds. Several products are sold under the following
trade names: Dynaweed, Safe N'Simple, Earth
Friendly, WeedBAN, W.O.W.! Corn Gluten Meal Herbicide,
Propac, and Concern Weed Prevention Plus.
For more information, visit the Iowa
State Corn Gluten Meal Research Web site.
To kill the roots and seeds of weeds (along with insects and other soil pathogens)
in a selected area, cover that area for 4-6 weeks anywhere from
June to early September with clear plastic sheeting (1 mil thickness),
and seal the edges with soil to make the covered area airtight.
Wet soil thoroughly before laying plastic. Called "solarization,"
sunlight can raise soil temperatures as high as 140 degrees at the
surface and up to 100 degrees as far down as 18 inches. This
is real global warming! Remove plastic before planting. (Clear plastic
heats sub-surface soil better than black.)
Solarization is a safe, non-chemical, and effective method for controlling the host of pests and diseases which might be lurking in your garden soil, including harmful bacteria, fungi, and nematodes, as well as insect eggs, root-gnawing larvae, and weed seeds. For more information, read the fact sheet: Going Solar to Set Your Soil Straight. (PDF, 2 pp, 165K)
Act fast to eliminate the weeds that compete with your lawn and garden plants. Take care of weed problems early in the season when the soil is saturated by spring rains and weeds are easier to pull. The whole tap root of weeds like dandelions and thistles must be destroyed since new growth easily sprouts from pieces left in the soil. Pull weeds out with roots, or cut off weeds just below the surface with a hoe or asparagus fork. Be sure to minimize soil disturbance which can stimulate dormant weed seeds to sprout.
Remove weeds from your lawn before they set to seed. You can use a trowel or asparagus knife to remove weeds like dandelion, plantain, and clover if there are only a few of them. You can also use a natural preemergent herbicide, such as corn gluten early in the season.
Mulch Away the Weeds!
Mulch can be used to create a barrier against sunlight so weed
seeds cannot germinate and young weed seedlings are smothered. A
scant covering of mulch is needed, so use it sparingly. Compost
used as a top dressing on lawns can prevent many weed seeds from
germinating. In other situations, be sure not to pile mulch
against the base of trunks or the stems of herbaceous plants to
prevent crown or bark rot. Lawns can be spot treated using herbicidal
soap. Repeat applications will be needed for perennial weeds.
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To prevent infestations from cockroaches, ants, termites, and other indoor pests:
- Clean up food spills and crumbs immediately.
- Keep food lids closed.
- Repair leaking faucets and drains.
- Keep appliances and counters clean of grease and food.
- Store grocery bags away from food preparation areas.
- Move garbage collection area away from house; be sure containers can be securely closed.
- Caulk around doors, windows and utility inlets.
- Store firewood away from the house, and keep it elevated to avoid wood to soil contact.
- Put a one-foot wide path of pea gravel around house to deter pest entry.
- Install or repair screens in doors and windows.
- Repair cracks in foundation walls, especially basements.
- Dehumidify a wet or damp basement; improve ventilation in crawl spaces.
- Clean gutters and downspouts; be sure water is drained away from the house.
- Remove and compost leaf litter promptly.
- Trim shrubs and trees away from house.
- Install non attracting or yellow light bulbs for exterior lighting.
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Showers for Indoor Flowers
Shower your houseplants with a healthy dose of water. Drenching plants in water washes off any pests that are claiming your plants as their home. Rinsing the leaves thoroughly with tepid water also rids plants of accumulated dust that blocks out the weak winter sun. In the winter months, amount and intensity of light decrease; low light levels slow your houseplants' growth. With decreased vigor, fertilizer and water requirements also decrease. Water infrequently and don't fertilize until late winter when sunlight increases.
Spidermites are known to strongly "dislike" the aroma of eucalyptus. Keep those pests at bay by purchase a package of fresh eucalyptus from a florist and cut sprigs approximately three inches long. Place a sprig in each of your indoor plant pots or hanging baskets, especially those most prone to spidermite infestations. Change the eucalyptus sprigs each spring to keep them effective.
Are you seeing white, waxy insects on your houseplants? Mealybugs are a common houseplant pest that infest all plant parts including the roots. Foliage becomes discolored and deformed due to mealybugs feeding on the sap. Mealybugs live in groups scattered throughout the plant so if you see some, it's likely there are more on the roots or elsewhere. Mealybugs secrete a white waxy substance that protects them and makes them tough to control. Hand removal is the most effective means of control, but dabbing individuals with cotton swabs saturated with alcohol will work as well. Mealybug populations may overwhelm you and your plant. Don't be afraid to throw out heavily infested plants. Scrutinize other plants in close proximity to your infested ones and also new plants you bring into your home for this troublesome pest.
Watch your indoor cyclamen, African violets, begonias, and ivy for deformed, curled growth on newly expanded leaves. The cyclamen mite could be causing the damage. Young flowers become distorted and fall early. Leaves also become wrinkled. Cyclamen mites are tiny; adults are less than one millimeter long an cannot be seen without the aid of a hand lens. Adults are translucent with a pale yellowish brown color. Females can reproduce without males so populations increase very quickly. They seek shelter in the protected crevices of young leaves. Cyclamen mites are killed by exposure to full sunlight. Control can be achieved by washing plants thoroughly and putting them under direct light for at least two hours. You can also dip plants in a half strength solution of insecticidal soap or horticultural oil to kill the mites. Other agents cause similar growth patterns so you'll need to identify the presence of the mite before you treat your plants.
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