Hill Gardens of Maine - A Few Highly Effective Natural "Insecticides"

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All About Those "Natural" Insecticides
by Fred Davis, MG, Hill Gardens, Palermo (To view other previous articles, click Archives)

Welcome through Fred's Garden Gate! So… we’re now back indoors, where ‘gardening’ becomes the nurturing of a few houseplants, re-reading our horticultural libraries, delving into newly-arrived Spring-2000 catalogs, and analyzing last seasons’ successes and failures. It’s also a splendid time, I think, to deepen our understanding of just what makes a successful garden ‘tick.’ Natural – or biological – insecticides seem a natural beginning point.

A biological insecticide is one which either controls or repels harmful or noxious insect pests, while having little impact on beneficial insects (like bees, dragonflies, ground beetles, for example), humans, or wild and domestic animals. They are a viable – and economical – alternative to less safe and oftentimes powerfully dangerous chemical pesticides seen in great abundance in farm ‘n garden shops, garden centers, hardware stores, even grocery and ‘super’ drugstores.

But today’s’ marketplace also literally abounds in biological insect, home and garden pest and plant disease remedies. Let’s take a closer look at a few highly effective, non-chemical alternatives.

DIPEL (or BT), actually Bacillus thuringiensis var. "kurstaki", is used primarily for the control of larval (caterpillar or ‘worm’) stages of a great many moth types and certain crop-damaging butterflies (not the beautiful and colorful Monarchs, Painted Ladies and Swallowtails but, rather, those which result in cabbage loopers and similar types). It leaves no harmful residue, is odorless and can be used up to the very day of harvest!

Used according to recommendations, Dipel is harmless to humans, our pets, even beneficials and fish, yet is potent enough to destroy – or at least control – loopers and worms, hornworms, and just about any other ‘worm’ which routinely damages fruit trees, garden ornamentals and forest species. Generally costing in the range of $5 to $10 for a home/garden-size unit, Dipel (also sold under trade names "Thuricide" and "BT") comes as a wettable powder or liquid concentrate.

PYRETHRIN, is one of my hands-down favorites! A true botanical biological ‘pesticide,’ pyrethrum is little more than the processed flowers of Dalmatian Daisy (chrysanthemum cinearaefolium). While pyrethrin has very little impact or negative effect on humans, honeybees and animals, and is readily available in most well stocked farm ‘n garden shops, it is pure death on flies, mosquitoes, moths, and a wide variety of food and ornamental crop pests.

Pyrethrin is also available in combination with another useful and effective biological, Rotenone. Both products are liquid concentrates to be mixed with water according to directions, and cost upwards of $10 to $12 per home/garden-size unit.

ROTENONE is actually extracted from the roots of bean-like plants commonly grown in South America and the Caribbean islands. Particularly useful defense against aphids, vine borers, squash bugs, Colorado potato beetles, flea and cucumber beetles, and a long list of caterpillar-like insects, rotenone can be safely sprayed as a liquid or dusted onto foliage surfaces. Destruction of pests is almost immediate and the material leaves little residue. Small, home/garden units of rotenone cost between $8 and $12, and are readily available wherever garden pesticides are marketed.

SAFER’S INSECTICIDAL SOAP is, as the name implies, ‘safer’ for both outdoor and indoor use than other, more toxic chemical pesticides. When mixed with indicated volume of water, applied spray has a not-unpleasant, saddle soap scent. Safer’s is free of petroleum substances, and is composed chiefly of fatty organic acid salts, giving it a ‘soapy’ appearance and feel. It is safe for use around humans, animals, birds and most beneficial insects – notably bees. Use Safer’s to control undesirable insects like mites, aphids and whiteflies on vegetables, garden ornamentals, and on fruits, shrubs and houseplants. A 16-ounce bottle of Safer’s liquid concentrate will make about six-gallons of spray, and carries a price tag of about $12.

One final thought: As with any concentrated material used in the control of insects, even ‘safe,’ natural biologicals should be handled with caution. Always wear gloves while mixing and at least a painter’s mask (like you see doctors and nurses wear on TV shows like ER) while actually spraying. Avoid over-heavy applications that can cause more than a drop or two to fall on soil – good gardeners can’t afford to lose a single earthworm or predator beetle! And lastly, always follow label directions and precautions to the letter, and keep concentrates (yes, even the ‘safe’ ones) stored where small children and pets can’t get at them because, even though they don’t have the old skull and crossbones symbol on the label, they should always be handled and stored with respect.

Now that you have the ‘scoop’ on completely natural – and infinitely safer – insect control, why use anything else?

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