Insect Control – Part Three

CaterpillarPhysical Controls

Physical methods, including traps or hand-picking insects off of your plants, will destroy pests before they can cause extensive damage.

Patrol your garden with a bucket of soapy water, into which you drop insects you pluck off your plants. Spread a cloth or plastic sheet beneath your plants and shake insects such as beetles off your plants.  Both of these techniques work best on cool mornings when insects are sluggish.

Water sprays are another effective nontoxic means of killing pests. The mere force of a strong spray of water will knock delicate aphids off plants and kill or injure them. Spray the underside of leaves with water from a powerful nozzle to wash off aphids and mite, and do so in the morning to avoid damaging foliage during the heat of the day.

Floating Row Covers 2


Floating row covers are lengths of synthetic fabric that you drape over your plants as a physical barrier against pests. They allow more than 80% of sunlight to reach your plants, and pose no barrier to rain or irrigation. The microclimate under the cover is warmer and more humid, thus extending the growing season.  Floating row covers provide season-long protection and are most useful for food crops. Drape them over your plants and bury the edges of the fabric in the soil, while allowing enough slack to allow for plant growth, or take the cover to a lightweight frame such as bamboo to allow for easy removal for weeding and other garden maintenance.

Collars are stiff cylinders constructed of cardboard or plastic that encircles plant stems at the soil level, acting as a physical barrier to such pests as cutworms. Fill the collars with wood ashes or diatomaceous earth to root maggot flies. You can make your own collars out of paper towel or toilet paper tubes. Encircle your seedlings as soon as you plant by pushing the collars into the soil.

Tree bands are barriers placed on the trunk of trees to prevent pests from crawling up the trunk. These work especially well for older gypsy moth larvae as they commute daily from the treetop down the trunk to hide in leaf litter during the night, and then climb back up the tree to feed during the day. Make a tree band by tying bands of cotton cloth or burlap around the trunk, with a string at the middle of the cloth, leaving the loose top section of cloth to flop freely as a dead end for pests. Regularly check your bands for pests and destroy them.


Copper is toxic to snails and slugs and an effective barrier against them. Wrap strips of copper around tree trunks or plant stems, or use copper edging to protect flower and garden beds.

Ants feed on aphid secretions and have been known to domesticate them, carrying them to establish an aphid colony that they then tend to and defend from predators.  Simple inverted pie plates, with a hole corresponding in shape and size to the leg of a greenhouse bench, will prevent ants from reaching the table surface. Coat the underside of the pie plate with a tacky substance such as the commercial product known as Tanglefoot.

Dehydrating dusts destroy the waxy coating on the exoskeletons that protect insects from water loss. The resulting damage dehydrates the insects and eventually causes death, so many pests actively avoid them.  To make your own, combine ¼ pound of diatomaceous earth with one teaspoon pure liquid soap such as Ivory, adding enough water to create a thick paste. Apply this as a ring around tree trunks to deter ants and many adult boring pests. For a garden application, spread diatomaceous earth, wood ash, or talc in a complete circle around the area you want to protect.

The best traps mimic the complex cues that insects use to find food or mates. They usually include a lure, such as a particular color or odor, and a physical trap, such as a sticky surface or a liquid such as water.  Many sticky traps are yellow because that color attracts many species. Many flies will land on bright yellow sticky traps, as will gnats and aphids. Make your own by painting cardboard bright yellow paint. Long, rectangular or oval shapes are the most attractive to insects. Coat your traps with a commercially available product called Tangle-Trap, Stiky Stuff, or even STP oil treatment, but use caution, as these substances will be sticky to you too.

Bug zappers use ultraviolet light to attract and electrocute insects. They are indiscriminate however, and are as likely to kill beneficial species as they are to kill pests.

Pheromone traps release a substance that insects use to attract mates. These pheromones are placed within traps and the insects are lured to it. These traps are especially effective at targeting a single species of pest without harming other beneficial species. Pheromone traps are commercially available for a great many species of pest.

Baited traps use some form of bait to lure the insect in, usually a favorite food, or something that indicates the ideal conditions for laying eggs. Fermenting fruit attracts Japanese beetles while slugs prefer beer. Use potatoes for wireworms, or sprouting onions for maggot flies.

Part Four will wrap up organic insect control with non-toxic chemical options.


Chemical-Free Yard & Garden: The Ultimate Authority on Successful Organic Gardening, Fern Marshall Bradley, Editor

Insect Control – Part Two

Cultural Controls

Keeping your plants healthy and your garden clean minimizes opportunities for pests to reach problem levels. Nutrient balance is important. Too much nitrogen in soil amendments results in leaves with too much nitrogen, which is more attractive to certain pests, such as sucking insects like aphids, mealybugs and scales. Use a balanced organic fertilizer to prevent imbalances that attract pests and to ensure that the health of your plants is their best defense.


Do not over- or under-water your plants. Dry conditions in your garden encourage spider mites and thrips to acquire the moisture they need from your plants. Certain pests like aphids prefer plants that are in a state of water-stress.  Dry soil conditions can create cracks that expose plant roots to pests.  Your plants need the equivalent of an inch of water every week during the growing season.

Pruning dead branch

Sanitation is important during all stages of gardening, including when you purchase your plants. Make sure that new arrivals do not harbor pests. Prune any branches or fruits that have been damaged or infected by insects. Burn these clippings to destroy the pests.




Biological Controls

Your best allies are the many natural predators and parasites of pest insects. These biological controls are inexpensive and effective, and have the potential to control pests indefinitely.

Biological controls vary from predatory insects that prey upon your pests, to parasites that infest and weaken or kill them.  The best way to encourage beneficial insects to remain in your garden is to provide them suitable habitat. An meticulously manicured garden without weeds and tilled every season is a barren habitat and unlikely to maintain adequate populations of beneficial insects. A diverse garden with permanent beds and walkways, with patches of wild vegetation or weeds, provides the shelter beneficial species need.

Organic gardening in itself is one of the best methods of encouraging beneficial insects, because it avoids the use of toxic pesticides and herbicides that weaken or kill the desired species as well as the pests.

Queen annes lace

Many beneficial species are predatory only in one life cycle and rely on pollen or nectar in another. Cultivate companion plants as sources of pollen and nectar. Companion plants that host beneficial insects include:

  • Dill
  • Caraway
  • Fennel
  • Lovage
  • Parsley
  • Queen-Anne’s-lace
  • Nettles
  • Wild mustard
  • Catnip
  • Hyssop
  • Lemon balm
  • Rosemary
  • Thyme
  • Coneflowers
  • Daisies
  • Yarrow
  • Goldenrod

You can supplement your local population of beneficial insects by buying predators or parasites as packaged biocontrols, but do so with caution. Be sure you know exactly what the introduced species is capable of, to the benefit and detriment of your garden. Be certain that you meet these criteria:

  1. Correctly identify your pests. Many biocontrol species such as parasitic wasps prey upon only one species or family of pests.
  2. Verify that your pest population is localized. If your pest has infested an entire region, such as the gypsy moth, your efforts to release biocontrols on the small scale of your garden will likely be ineffective as pest insects will continue to migrate into your garden from beyond your property.
  3. Make sure that your biocontrols, once released, will not be decimated by drifting pesticide spraying on adjacent land.

Your pests are as susceptible to diseases as are your plants. There are microbial insecticides on the market for home gardeners, including bacteria, fungi, nematodes, and viruses. Most diseases are a long-term strategy, as the pest species must eat the bacteria or virus to become infected, unlike with fungal spores, which penetrate the insects’ exoskeleton upon contact. Below are just a few examples.

Bacillus thuringiensis (BT) is the most widely used biological control on the market today. Insects eat BT spores, which then dissolve in stomach acids and paralyze the gut, followed by multiplying in the blood stream, resulting in death by starvation, blood poisoning and bacterial infection. While nontoxic to humans and other mammals, BT is a bacteria whose spores are toxic to certain insects, including caterpillars and some species of flies and beetles. It doesn’t last long in the environment, but beware, as caterpillars are the larvae of desirable butterfly species.

Milky disease spores are used against Japanese and June beetles. Beetle grubs eat the spores and produce a milky white liquid filled with bacteria.

Our next post, Insect Control – Part Three, will continue insect controls methods with physical techniques, followed in Part Four with chemical methods.


Insect Control – Part One

Lady BugOrganic insect control is one of the easier organic gardening techniques. There are numerous methods and products to rid your garden of insect pests. Encourage your garden’s natural defenses against pests, and let beneficial insects and organisms do the work for you.

Identify Your Pests

You may notice chewed leaves in your garden, but be unable to spot the culprit. It is possible that the larvae or grubs responsible have already left your garden, as it is common for caterpillars and beetle larvae to gorge on plants in the very last few days of that stage of their life cycle. To determine if your pests are already gone, examine the most recent growth on your plants. If that is undamaged, it is likely the pests left before such growth appeared. Another sign that damage is old is that the edges of holes will dry out and turn brown, while fresh holes retain a clean sharply-defined edge.

If you determine that your pests are still present, here are some brief guidelines for matching the pattern of damage to the insect that caused it.

Caterpillars Eating

If you have large, ragged holes in your leaves, they were most likely chewed by beetles or caterpillars. If the holes are tiny, it was done by flea beetles.

If a trail of slime accompanies the ragged holes, the damage was caused by slugs. Leaves that have curled, twisted or appear wilted are the victim of aphids, leafhoppers or thrips that have sucked the moisture from them.

Bug Bite

Leaf weevils chew neat half circles, like little bites, from the edges of leaves. Larvae are usually responsible for damage to roots. A fine web that has curled a leaf in upon itself into an enclosure is evidence of the presence of leafrollers, who feed within the safety of the curled leaf, whereas a web that develops from the underside of leaves is the work of spider mites, often accompanied by white or yellow specks on leaves. Damage to seedlings at the soil surface is caused by cutworms. If leaves have twisted tunnels running through them, it is leafminers that have caused the damage, as they feed on internal leaf tissue.

Once you have narrowed the field of suspects, use a field guide to determine the exact species of pest.

Look for our next post, Organic Insect Control – Part Two, to learn safe, non-toxic methods of controlling insect pests in your garden.

Organic Disease Control

Fungal OnionAvoid dangerous fungicides with these simple steps to prevent disease and protect the health of your garden.

Know the Basics

Fungi, bacteria and viruses cause disease by living within host plants or devouring them, and each of these organisms causes distinctive symptoms to develop in your plants. The symptoms exhibited by your plants will be the key in determining what disease you are dealing with.

FungiGall 01

Some species of fungi live only on dead organic matter, such as many of the fungal species responsible for decomposition, while others prefer live plants.  Some are capable of attacking both living and dead tissue, choosing live plants during the growing season and surviving quite well on dead material to overwinter. Their method is to release toxins that kill plant cells, thus weakening the plant and enabling the attack. Fungi propagate by releasing air-borne spores that can germinate immediately, or lie dormant for years waiting for the right conditions to develop.

Fungi are responsible for more plant diseases than bacteria or viruses. The damage can appear at the base of stems, the crown of plants, or within the foliage, flowers or fruit. Symptoms include rotting tissue, mold, spots, wilting, and leaves with blisters or curling. Smut is a sooty mass on grains and grasses. Galls are a form of swelling or abnormal growths. Powdery blisters on leaves that are either reddish brown or yellowish are known as rust.

Fungi are dependent on moisture and thus good soil drainage is one method of controlling them. Improve soil drainage by adding organic matter or planting in raised garden beds. Air circulation also prevents moisture from building up on flowers, fruits and foliage, so space plants so that air can circulate between them.  Avoid gardening under wet conditions to prevent the spread of spores. When watering your plants, avoiding wetting the leaves, and water early in the day so that your plants have time to dry during the day. Prevent damage to your plants, as damaged tissue is easier for fungi to attack. Remove all diseased parts of a plant as soon as you notice symptoms and only compost that material in a hot compost pile where temperatures exceed 160 degrees or dispose of it in sealed plastic bags or by burning.

Bacteria InfectionBacteria

Bacteria are microorganisms that cause a variety of blights in stems or rotting in leaves, stems, crowns or fruit, characterized by slimy and smelly tissue. Bacterial infections can result in the release of a foul order, which helps distinguish them from a fungal disease.

Bacteria can survive the winter in decomposing plant material, in hibernating insects, in galls on living plants, and in your garden soil. They can survive for years within a host but unlike fungi, do not have extended periods of dormancy.

Healthy plant tissue is an effective barrier to bacteria but any bruising or damage will enable bacteria to circumvent such defenses.

Remove damage sections of plants immediately upon noticing symptoms of disease. Burn or dispose of this material in the trash, if your compost does not exceed 160 degrees.


The symptoms of viral diseases are similar to those of nutrient deficiencies, such as stunted or abnormal growth, mottling, streaks, or spots.

Viruses are most often transmitted by an insect host such as aphids or leafhoppers, or other sucking or chewing insects.

Hot compost is ineffective in killing viruses, so once you have removed diseased material from your garden, burn or dispose them in sealed containers with your household trash.

Cultural Controls

The first step is to choose cultivars that are resistant or at least tolerant of disease. They often accomplish this by differences in their biological chemistry or by structural difference such as thicker tissue or leaf pores that open at a time of day not beneficial for the disease.

Healthy soil is a critical component of your garden’s defense against disease. Plants grown in healthy soil have balanced nutrition and proper moisture and aeration, and are thus more vigorous and better able to defend themselves against disease.

Watering frequently increases humidity around plants and creates ideal conditions for rot. Water early in the day, so that the surface of leaves can dry before nightfall, and water less frequently but more deeply so that water percolates deep into the soil.

Clean your garden annually, in the autumn, to reduce pest, weed and disease issues as this will minimize the opportunity for organisms to overwinter successfully in your garden. Clean your gardening tools regularly to prevent the spread of disease.

Physical Controls

Once you have identified the symptoms of a disease, remove the disease organisms from your garden.  Remove leaves, stems, fruits or flowers that show signs of disease. If the root or crown is rotting, dig up the entire plant, including the roots and nearby soil, and dispose of them in sealed containers.

Mulch not only protects against weeds, it also prevents some fungal spores from spreading through splashing rainwater.

Trellises and staking promote air circulation, as does pruning, but do so carefully. Sterilize your tools between each cut with a 10% bleach solution, and prune back to a healthy bud or main limb, as a bare stub of woody material will simply be another entry point for disease organisms and pests.

Chemical Controls

In an organic garden, chemical controls involve the use of growth-enhancing sprays or natural fungicides and bactericides.

Growth enhancing sprays contain nutrients and hormones that encourage vigorous growth, enabling your plants to more successfully fight of disease. You can make a natural spray at home from stinging nettle.

Gather one pound of stinging nettles. Crush them and put them in a cloth sack or pillowcase. Soak the sack in one gallon of unchlorinated water in a covered bucket in a warm place. After one week, carefully open the bucket, as the odor will be strong. Strain through a cheesecloth and store in glass jars for no more than one month. Spray your plants to repel aphids and administer a dose of trace nutrients.

A .5% solution of baking soda helps to protect against fungal diseases, especially in roses. Dissolve one teaspoon of baking soda in one quart of water. Add a few drops of liquid soap and spray on infected plants, including the underside of leaves.

Sulfur has been used as a fungicide for thousands of years. Fungal spores cannot germinate in a sulfur film. Preparations of it are sold as a powder or liquid.

Our next blog will be on Insect Control.


Chemical-Free Yard & Garden: The Ultimate Authority on Successful Organic Gardening, Fern Marshall Bradley, Editor



Organic Weed Control

DandelionsWeeds compete with your garden plants for nutrients, water, space and light. They may also harbor pests and diseases, may be poisonous, or may cause allergies. They often seem impossible to eradicate, which has led many gardeners to use chemical herbicides to control them. Chemical herbicides contain toxins that are hazardous to those that apply them and to anyone who comes into contact with them, including not only those in your own household, but your pets, your neighbors, and wildlife. They are poisonous to the beneficial insects that could benefit your garden. These toxins are persistent, meaning that they remain hazardous in the environment long after rain has washed them from your yard and into ground- or surface-waters.

Here are a few basic gardening techniques to control weeds in your yard and garden without resorting to hazardous chemicals.

Cultural ControlsMulched

Incorporating a few simple techniques into your regular gardening routine can help you avoid weeds before they can become established. Use mulch liberally to deny weeds the opportunity to take root. It is not only one of the easiest and most effective ways to control weeds, it also increases soil fertility through its gradual decomposition.  Mulch also reduces water loss from soil.

Prevent your weeds from contributing their seeds to your soil’s seed bank. Patrol your garden regularly and pull all weeds that are blooming. Remove these pulled weeds from your garden completely. If you have a hot compost pile, where decomposition reaches temperatures hot enough to kill seeds, you can safely compost your weeds. If your compost does not reach 160 degrees or higher, throw your weeds into the trash so that the seeds do not germinate in your compost bin.

HoeingPhysical Controls

Physical control of weeds includes the time-honored techniques of pulling weeds by hand and hoeing. Hoes are sold in a variety of shapes and sizes. Hoeing works best for those weeds that are killed when their stems or growing crowns are cut from the roots. Pulling weeds by hand is the best method to use on weeds that are growing closest to your garden plants.


Chemical Controls

As a last resort, organic gardeners may rely on vinegar, salt or soap-based preparations to control weeds. Vinegar and salt both have detrimental effects on a soil’s delicate balance and should only be used on soils where you don’t want anything to grow at all, such as the ground on which you plan to lay a paved path or between established paving stones. Vinegar is in fact a dilute acid and will acidify the soil, which interferes with the ability of roots to absorb water and nutrients. Use vinegar and salt only when there are no other alternatives, and even then beware that the potential harm to your garden may well outweigh the possible benefits.

Weeds in Cracks

A number of new organic herbicides have been developed. These herbicides are based on fatty acids such as herbicidal soaps, various dilutions of vinegar, or essential oils such as citrus or clove oil. They can be found at well-stocked garden centers or online. For best effect, apply herbicides when weeds are young, and at the hottest, sunniest part of the day.

Our next topic will be Disease Control.


Chemical-Free Yard & Garden: The Ultimate Authority on Successful Organic Gardening, Fern Marshall Bradley, Editor