Organic Pesticides Guide

Using pesticides and herbicides need not be synonymous with toxic chemicals that harm our health and our gardens. There are many natural techniques, home-made recipes and commercial organic sprays that are effective without harming the surrounding environment.

The problem with pesticide sprays, besides introducing yet more chemicals into our system, is they often kill the “good” insects that would otherwise help us combat problem pests. The spray that kills aphids could also kill dragonflies, butterflies and honeybees. In fact, 95% of all insects in your garden are either harmless or actually help your plants. With that in mind, spot-treating is much better than going over your entire garden with a spray.

As organic gardeners, we need to find natural and safe products to keep the bugs away and control weeds from messing up our gardens. Fortunately, they are available, and they are often already stocked in your kitchen! (See a list of home-made recipes.) Commercial products are also becoming increasingly available, all made of organic ingredients that are safe for your health and your garden.

• Natural Pesticides – Pyrethrum, garlic, hot peppers, etc

• Natural Herbicides – Citrus oil, corn gluten meal, neem, etc

• Natural Fungicides – Copper, sulfur, baking soda recipe, tea tree oil recipe, etc

Natural Pesticides

Pesticides in the Kitchen and Garden

Garlic
Garlic wards off vampires, and it also repels insects like aphids, and even prevents the spread of certain diseases! In fact, it is a great all-purpose pesticide for your garden. Plant edible garlic between rows of vegetables or roses to repel aphids and other insects. Use garlic powder mixed with water to use as a spray on plants – careful though, too much will harm them. Keep it to one spray. Commercial versions are often safer and more effective, as they have been extensively tested.

Anise
Plant anise nearby to ward off aphids, fleas and cabbage pests.

Catnip
Catnip deters many pests such as Colorado potato beetles, squash bugs, weevils and even ants.

Hot peppers
Many people can’t stand hot peppers, but insects absolutely loathe them! Keep some bugs out of your garden with a small amount of pepper juice or pepper seeds and water, then lightly coat your plants.

Beneficial Insects
If the insect problem isn’t too bad or out of control, you could just wait for the cavalry. If your garden has been broad-spectrum pesticide-free for a few months, predatory insects will find the infestation and lay their eggs next to this valuable food source. Yum yum, aphid stew!

• Learn more about your insect army, and where to buy them

Natural Herbicides

Organic gardening weed control involves the long-term planning of encouraging your plants to crowd them out, and keeping your grass healthy and thick so weed seeds can’t develop. Just like the plants in your garden, weeds (that is, “any plant that shouldn’t be there“) need air and sunlight to flourish, so preventing them from growing by covering the soil with newspaper, mulch, bark, stone and, of course, your big, healthy, bushy plants will block them from growing and spreading.

Here’s a couple techniques and products to help control weeds:

Corn Gluten Meal for lawns

For weed seeds, such as dandelions, spread corn gluten meal over your lawn to prevent seeds from germinating. Corn gluten meal is a natural byproduct of corn starch, and is used in animal feed, taco shells and chips, and pet foods. As a bonus, it is a great source of nitrogen fertilizer. It does not harm existing plants, only seeds, so spread liberally in your flower gardens, but not in your lawn if you are reseeding. Apply in early spring, and then reseed your lawn six weeks later when the corn gluten meal has broken down.

Tests show corn gluten meal reduces crabgrass by 86% the first year and 98% the second year, using proper applications in the spring and fall. In a 4 year test, dandelion infestation on a test plot was reduced by 100%. (University of Wisconsin)

• Try WOW! Supreme lawn fertilizer, one of the effective commercial brands listed at the University of Wisconsin’s page.

• More information and a list of manufacturers (WOW! is listed at the bottom.)

Vinegar, garlic and clove oils

Vinegar, garlic and other oils have long been a weed control method. What they do is burn the leaves, quickly browning them. However, unless the weed is very young, it does not kill the roots. That means that in a week or two, the weed will say “Hello, I’m baaaack!”, taunting you once again. Hand weeding is easier.

That being said, stronger (11% acetic acid or higher) vinegar is much more powerful against weeds, including the roots. Regular commercial vinegar is around 5%, so this will only burn the leaves of the weeds. Stronger vinegar solutions will be sold as a herbicide, and may be found at some gardening centers and online, such as Amazon.com. Be aware that strong vinegar is dangerous, so handle with care and definitely do not get any in your eyes!

Mulching and soil coverings

Mulching is by far my preferred method of weed control. Mulch not only blocks weeds from growing, it is a common and effective practice of naturally fertilizing your lawn. Natural mulch includes grass clippings, slightly decomposed wood chips (fresh wood chips actually draw nitrogen from the soil), pine bark, straw and even coffee grounds.

You can, of course, use non-organic soil coverings to prevent weed growth, such as plastic sheets and rubber mulch from recycled tires (hey, at least it’s putting trash to work!), or decorate rocks and gravel, but none of these decompose and add nutrients to the soil.

Natural Fungicides

Controlling plant disease involves similar long-term planning. Diseases include root-rot, black spot, powdery mildew and bacteria such as rusts. The best preventative measure? Keep everything clean! It may seem obvious, but plant disease can only spread if it is given the chance. If fungi and bacteria spores are not given the chance to thrive at the expense of your plants, you will not have a problem. Here are some practices to follow in your day-to-day gardening:

• Remove diseased materials – quickly clean up fallen leaves, carefully snip off diseases areas of the affected plant. Place these straight in the garbage – do not place them in your compost bin, as they can then spread and affect surrounding compost materials
• Clean your gardening tools and clothing – After treating a diseased plant through pruning, wash your tools in bleach or other sterilizer. A lot of disease is inadvertently spread by you, either through spores on your clothing or through your tools
• Practice intercropping – Diseases are usually plant-specific. One type of fungus will only attack one type of plant. With that in mind, if you do not care about the uniform look of a garden, try planting similar plants in different areas. For instance, if you have two or more rose bushes, do not plant them together. That way, if one becomes infected, it likely will not spread to another one, because there will be a different species of plant in the way (such as garlic chives, which will actually protect your roses from many insects and diseases in the first place!)
• Healthy plants equals less disease – Another obvious point, but if your soil is rich and healthy, your plants will be strong and vibrant, and thus able to ward off a smaller number of fungi and bacteria spores in the air.

Fortunately, there are many natural products that will combat fungus and molds. Here are a few to try, depending on the type of problem you are having:

Beneficial Fungus on transplants
Many destructive fungi live in the soil and attack the roots, so why not have your plants “inoculated” by introducing a beneficial fungus instead? These organisms are naturally occurring in rich, healthy soil, and will bind to your plant’s roots anyway, out-competing bad fungus. Sprinkle some of this in the root ball or in the planting hole before transplanting.

• Root Maximizer from Abico Organics

Copper to combat rusts, mildews, scabs and more fungal diseases
Copper compounds have been used for a long time to control a wide variety of diseases. They attack the germination of spores, so they help prevent further spread of the disease. A warning, though – copper products, such as copper sulfate, is toxic to humans, mammals and aquatic species, so care must be taken. As with all pesticides (which are, after all, poisons, synthetic or organic), must be treated with care. Always follow the directions on the label!

• Bonide Liquid Copper Fungicide from Abico Organics

Sulfur
Sulfur has been used since the Greeks and Romans, and controls the spread of disease such as black spot and powdery mildew. Like copper, it inhibits the growth of new spores. It also repels spider mites and thrips, but it is also toxic to some beneficial insects, so only spot-treat plants. Sulfur is also used to reduce the pH of soil.

• Sulfur Plant Fungicide from Abico Organics

Home-made Herbicide and Fungicide Recipes:

Baking soda (Sodium Bicarbonate)
Used to combat fungi that attacks plants, such as mildew. Combine 2 tablespoons of baking soda, 1 gallon of water, and 1 teaspoon of vegetable oil. Mix thoroughly and place in a spay bottle. Spray on contact. Not very effective against black spot.

Tea tree oil
All oils have the potential to burn plants, so use sparingly. That being said, insects hate vegetable-based oils, and olive and tea tree oil prevents and actively combats fungus on leaves. Combine 2 tablespoons of tea tree oil with two cups of water. Mix well and place in a spray bottle. Spray on contact. Also works great as an antiseptic and air freshener (though very strong-smelling.) We use it in our child’s diaper pail to neutralize smells.

Soaps

Like oil, use soap sparingly. Soaps are effective on young weeds because it strips the waxy layer off the leaves, drying them out. (A similar process makes insecticide soaps effective as well.) However, for the same reason, they could harm your existing plants as well. A small portion of liquid or tea tree oil soap, mixed with lots of water and spray, is an effective fungicide and insecticide.

My organic gardening book lists sixteen products to use as natural pesticides and herbicides!

Arbico Organics sells a large variety of organic insecticides, herbicides and fungicides. They even sell live beneficial insects and plant mixes to help keep them in your garden. Raise an army of natural defenders!