Since the dawn of agriculture, when humans realized seeds were next season’s plants in storage, man has had a love-hate relationship with nature. But it all comes down to this: Plants are our planet’s food. Directly or indirectly, they sustain every living thing on Earth, and we’ve been waging a longstanding war against pests to secure our fair share and then some.
There’s evidence humans used sulfur as an insecticide more than 5,000 years ago. This means chemical aids are only the latest tools in our effort to control pests. Organic methods, on the other hand, have had a 5,000-year head start, which is plenty of time for nature to have developed effective, environmentally friendly strategies to help plants beat bugs, bacteria and fungi.
Is Organic Always Better?
Before we start looking at organic pest control options, it’s important to recognize that the term organic doesn’t always mean safer, although it can, and words like chemical and synthetic aren’t synonymous with words like dangerous or unhealthy.
The term organic simply means derived from nature, or a substance or process that does not use synthetic chemical components or hormones. It sounds good, but keep in mind that while vinegar is organic, so is arsenic, strychnine and cyanide. While these poisons are organic, you don’t want to treat your crops with them.
The US Department of Agriculture has loosened restrictions on the use of some types of relatively benign chemical treatments on crops sold as certified organic, and has issued cautions about some broad-spectrum organic solutions. These actions remain loyal to the spirit of organic labeling, while still addressing some of the problems presented by today’s persistent pests. Depending on what and how you grow, you may find yourself dealing with a similar type of balancing act in your outdoor or indoor garden.
Choosing Your Organic Weapons
The best organic pest control solution for you depends on where your garden is located, how big it is, what you are growing and what pests represent the biggest threat. Some organic methods are preventive, while others are trench warfare, pitting beneficial insects against destructive ones. Some techniques use microbes, while others rely on pheromone traps, and still others employ colorful lures.
A few techniques inject plain old common sense into the mix, while the most aggressive techniques rely on naturally derived insect poisons. What’s the best natural method? There’s no right answer! The best method—or combination of methods—is the one that works for your specific situation, the discovery of which will probably take a little observation and research.
Organic Pest Control Options
Let’s look at the most effective organic solutions you can use to discourage pests, starting with the least invasive first.
If your small garden is plagued with insects you can get a grip on, just pick them off your plants and drop them into a bucket of soapy water. Leave the bucket upwind of your veggie patch or favorite flowerbed, and the smell of dead Japanese beetles or tomato horn worms may discourage others from encroaching on risky territory. It may seem like an unpleasant job at first, but after a few sessions and the diligent use of garden gloves, most gardeners become desensitized to this process and consider it a good way to get up close and personal with their plants. Your efforts will provide you with important information, such as when specific bugs are most active, what types of plants they prefer and where their eggs and larvae are hiding.
Covers and Barriers
Erecting a barrier between your plants and the pests that want to make a meal out of them is a classic pest control solution. If you have an indoor garden or greenhouse, you know this plan isn’t foolproof, but it has merit.
While row covers and other barriers reduce pest problems, there is still a threat from pests that burrow into the soil under plants, and windborne eggs, larvae, spores and other threats that can pass through wire mesh or fabric. Barriers may also reduce airflow to plants, and make weeding and plant pollination more difficult. Adding a barrier may seem like an extreme solution, but with pesky invaders like rabbits, and pesticide-resistant insects, it might be the best way to take back control of your garden.
Traps use pheromones to lure and kill large quantities of destructive insects. They sound like a good idea, but they are often not enough. An epic fail can occur when there are too many insects for a trap to handle. A study conducted by the USDA found that even under optimal conditions, Japanese beetle traps catch about 75% of the beetles that approach. Without close monitoring and other complementary pest control measures in place, using traps can result in increasing pest populations instead of eliminating them.
Another pest control option is drawing pests away from specific crops. For example, a bright-yellow squash flower is a beautiful sight for a squash beetle. If you plant other types of yellow flowers—possibly a few sacrificial squash plants—and even place some yellow plastic tape in another part of your garden, beetles will be drawn there, find what they want and leave your primary crop more or less intact. To increase the effectiveness of this strategy, intersperse catnip or other plants squash beetles dislike among your more prized plants.
Using catnip to repel squash beetles is an example of companion planting. Consider it the buddy system for plant protection. Strongly scented plants are often a turnoff for bugs, and some pests are especially vulnerable to specific scents. You can find long lists of companion planting suggestions designed for pest control. Some have been tested and verified, while others are anecdotal and may work only under certain circumstances.
Herbs like garlic, dill, fennel, tansy, feverfew and peppermint are often recommended as companion plants. Beyond companion planting with bug-busting herbs and flowers, you can harvest a handful of their leaves, toss them into a blender, add water and make a mean, green bug-repellent juice. Just pour the concoction into a pump sprayer and spritz liberally in your garden.
What and where you plant can make a big difference in how pests view your landscape. When you choose species of trees, shrubs, flowers and other plants that are not attractive to problem insects, you reduce your property’s appeal to pests. For example, Japanese beetles are attracted to roses, blueberries and peonies, but avoid hydrangeas, forsythia and larkspur. Planting an unappealing plant upwind from, or adjacent to, an appealing plant can sometimes help deter pests.
Just as some plants repel destructive insects, other plants attract beneficial bugs. Whether you’re wooing them from a neighbor’s garden or trying to maintain a purchased colony of bugs, making your landscape more attractive to beneficial insects won’t hurt.
For instance, a single ladybug can eat up to 60 aphids a day. That’s cheap and effective labor. Potential insect allies include praying mantis, spiders, braconid wasps, tachinid flies, pirate bugs, flower flies, soldier bugs, ambush bugs, lacewings and ground beetles.
Other Types of Biological Warfare
You can also wage a war on pests using beneficial bacteria, fungi and microscopic worms. These living organisms infect destructive insects, often during their early development as grubs or nymphs, and disrupt their biological functions or parasitize them, killing them from the inside out.
Colonies of beneficial microbes can be introduced to plants or to the soil, depending on the variety, and do not harm humans, pets or most beneficial insects. Beneficial microbes are vulnerable to chemical and organic pesticides, though. Some examples include milky spore (Bacillus popillae-Dutky), the Verticillium lecanii fungus, Bacillus thuriengensis (Bt), Heterorhabditis bacteriophora and other beneficial nematodes.
Desiccants rob pests of moisture by causing damage to their skins or shells. The two most popular desiccants are diatoms, which are microscopic, single-celled plants that have become fossilized, and boric acid. Both are relatively safe to use, although diatom powders (diatomaceous earth) should be reapplied after a rainfall or heavy watering. Ground-up eggshells can be used, too, but they are most effective against larger pests like slugs and snails.
Minerals can also be effective in controlling pests, bacteria, molds and fungi, although individual organic pesticide guidelines may exclude some mineral formulations. Common mineral pesticides include sulfur, calcium hydroxide (lime) and copper sulfate.
Organic Pesticides and Insecticides
Pesticides and insecticides are considered the heavy artillery of pest control. They are often the most effective, but are also the most potentially disruptive. Some organic pesticides may have less environmental impact than their chemical counterparts, but that’s because they remain active for only short periods, or are pest-specific, so their scope is limited. They are still poisons, and broad-spectrum pesticides may have negative implications for beneficial insects, aquatic environments and other wildlife. They may also require special handling techniques. Here are some examples:
Insecticidal Soaps – Insecticidal soaps are a mixture of potassium hydroxide and fatty acids derived from organic fats and oils. They damage the cell membranes of many soft-bodied pests, killing them with minimal environmental impact. To be effective, the liquid has to come into direct contact with the pest. Insecticidal soaps can have insecticidal, fungicidal and algicidal properties. In high concentrations, insecticidal soaps can damage tender plant leaves.
Oily Insecticides and Repellants – Many insects and their larvae and eggs are vulnerable to suffocation when coated with oil. Oil-based organic insecticides and repellents are among the most common organic solutions on the market. Neem oil, from the neem tree (Azadirachta indica), is one of the most popular. It is also antifungal, effective as a treatment for mildew and fungal problems like powdery mildew, rust and black spot. Other popular oils include garlic oil and preparations made with canola oil. As with insecticidal soaps, the oils have to come into direct contact with the pests to be effective.
Plant Extracts – Although insecticidal oils can be derived from plants, there are also plant-based sprays, essential oils and powders. Most are produced in higher concentrations than you’d find in homemade preparations. Plant extracts may be useful for their pest-killing properties (as poisons), or as strongly scented repellents (terpenoids). Pyrethrum, extracted from chrysanthemums, is one of the most effective and widely used organic, broad-spectrum insecticides.
It targets and destroys the nervous system in many types of insects. Rotenone, another broad-spectrum option, is a compound found in a number of plants, including Jícama and jewel vine. It is a stomach poison that causes insects to stop feeding almost immediately. Other botanical pesticides worth noting include sabadilla, from the sabadilla lily, and the most dangerous on this list to humans and pets, nicotine sulfate, which is extracted from tobacco.
No article discussing pest control, organic or otherwise, would be complete without mentioning prevention. Although some pest problems are an unavoidable part of gardening, others may be avoided completely. Removing dead and dying plants from your landscape, promoting healthy soil through testing and periodic correction, rotating crops and segregating new acquisitions until you know they’re healthy are basic steps you can take towards a healthier, more pest-resistant garden.