Organic Controls for Bugs and Diseases

These are all naturally occurring, organic chemicals, not synthetic or man-made, but they should still be used as a last resort and with caution. “Organic” does NOT equal harmless, my favorite example being that popular home remedy for everything that ails the garden — nicotine! Good old tobacco juice is just as effective at killing insects as it is in killing humans — maybe even more so — but do you want to use it? I didn’t think so.

Another warning: Most of these chemical treatments are nonselective, meaning they kill lots more than the organisms you’re trying to kill, and they can be slow-acting. Still, because they’re organic, most are less toxic and don’t persist as long as the synthetic products. The results are mixed but still worth trying if prevention or physical and biological controls have failed.

Anti-transpirants, like Wilt Pruf, reduce moisture loss from leaves and protect against fungal diseases.

Neem, an oil derived from the neem tree, kills insects and prevents fungal disease. Official sources declare it to be “relatively nontoxic” to bees and birds but toxic to fish. It degrades in the presence of sunlight and does not persist in soil. Gardeners report that it works to control aphids and blackspot on roses, lily leaf beetles, powdery mildew on plants like phlox and monarda.

Bicarbonate sprays containing baking soda are old-fashioned remedies to help prevent fungal diseases and can also be found in commercial form (for a lot more money). They work best when combined with horticultural oil and applied before infection occurs. There’s that prevention theme again.

Citrus oils used as fungicides and contact insecticides can be effective and are relatively nontoxic.

Copper sprays are used to prevent fungus and bacteria. They’re nonspecific, however, persist indefinitely in soil, and harm microorganisms and beneficial insects. They’re also highly toxic to aquatic life. Acme Bordeaux Mixture and Bonide Liquid Copper are the brands most commonly used.

Horticultural oils can be used to repel water and the fungi it carries and also to suffocate aphids and other insects on contact. On the plus side, they degrade rapidly. On the negative, they can damage leaves, so test first on a small area. They’re also toxic to many beneficial organisms and to aquatic life.

Insecticidal soaps (like the brand Safer Insect Killing Soap) are made from fatty acids that smother insects and kill them on contact (therefore not meant to be used as a preventive measure). Most are relatively specific and nontoxic to humans, but can harm beneficial insects and aquatic life. Many organic gardeners recommend them, however.

Pyrethrins are poisons made from a type of daisy that kill insects on contact. Because they persist only a few hours in sunlight, they’re one of the safest botanical products. BUT (and isn’t there always a “but”) pyrethrins persist when the conditions are damp, they’re nonspecific in what they kill, and they’re extremely toxic to aquatic life.

Rotenone, a contact and stomach poison derived from the roots of certain tropical plants, has been used for at least 150 years. Though widely sold, this is a very potent organic product that’s more toxic than many synthetics. It’s lethal to fish and aquatic invertebrates, also to some beneficial insects and even mildly toxic to mammals. And it persists a long time in the garden.

Sulfur has long been used as a fungicide in dust or spray form. While it’s effective in preventing powdery mildews on plants that are highly susceptible to them, it also kills beneficial soil microorganisms and insects. So who wants to grow highly susceptible plants anyway?

Iron phosphate pellets (brand name Sluggo) are reportedly safe and effective in killing slugs.

And a final note of caution about these organic products — you still need to wear gloves, follow shelf life recommendations, read the darn label, and dispose of them properly. That means no dumping on the ground, pouring down the drain or putting them in the trash. For help with disposal visit Earth911.org or call 1-800-CLEANUP. (So by now you’re thinking it’s easier to prevent these problems?? Exactly.)

Larger Animal Pests

Got deer, rabbits, or voles? The Internet is full techniques you might try against these pests, so I suggest you Google for answers because I’ve never confronted these pests and know nothing about them. Oh, except for squirrels, an animal I’ve lost some battles with myself, and I happen to have a home remedy that works to keep them from eating tulips. When planting, place bulbs in the hole, fill with soil to the top of the bulbs, add a few red pepper flakes, then fill the hole to the top. Thus the pepper is between the bulb and the squirrel and for some years now, it’s kept my tulips safe.

A Word About Switching To Organic

It’s not just a technique; it’s a philosophy. Organic gardeners learn to accept some leaf damage, wait and watch. Some amount of “bad” bugs are needed just to keep the beneficial bugs that eat them around. Get information about organic remedies from gardeners — not marketers — or from independent garden centers you trust.

Plants have to adjust, too. If your garden is addicted to pesticides, especially the synthetic ones, it can takes three or four years for it to come back into a healthy balance again.