How Green Are Natural Insecticides?

You've just planted a garden, and you want to protect your crops and your home from an insect attack. You'll have no shortage of insecticides to choose from — but which are effective? More importantly, which are safe?

You're not short of options. There's a whole range of synthetic insecticides guaranteed to wipe out every bug known to man. Or you can opt for an integrated pest management (IPM) system, which incorporates preventive measures with sparing use of eco-friendly insecticides.

Of the 1 million named insect species on Earth, about 1,000 are pests — and more than half of those are already resistant to synthetic insecticides.

In recent years, increasing emphasis has been placed on reducing the number of synthetic insecticides, which pose a number of other problems, including killing beneficial bugs and adversely affecting human health and the environment.

Many of the once-common insecticides such as chlorpyrifos (sold under the brand name Dursban), chlordane (sold as Ortho) and lindane are no longer sold for home and garden purposes, because they did their job too well.

Most insecticides, both synthetic and natural, interfere with insects' nerve transmissions. DDT, lindane and Ortho cause insect neurons to fire randomly, causing spasms and death.

They're less harmful to mammals, but in the environment they break down into toxic chemicals that can last for decades and poison all sorts of animals.

Natural, or botanical, insecticides such as pyrethrum work in a similar way, but they break down quickly upon exposure to sunlight, which limits their agricultural effectiveness. In low doses, they often repel rather than kill insects.

Dursban and related chemicals work the opposite way — they inhibit the enzyme cholinesterase, which lets nerves return to their resting states. Instead, nerves stay "on," paralyzing the insect and causing death.

They break down rather quickly, but their main problem is that mammals also use cholinesterase.

In fact, Dursban's bigger, badder siblings include the weaponized nerve agents sarin and VX. While Dursban is less lethal to mammals, it has caused a range of health problems, even death, among humans.

All insecticides gradually lose effectiveness as their targets mutate and build up resistance. But because they degrade more rapidly, natural insecticides have a longer useful life in the field.

In order to encourage the development of alternative pest management, the U.S. Environmental Protection Agency (EPA) in 1996 created the Biopesticide Division and the "minimum-risk" pesticide category.

Nowadays, before a pesticide can be marketed and used, the EPA conducts a full evaluation to ensure that it will not pose any risk of harm to human health or the environment.

As it became clearer that few synthetic insecticides were really safe, and that their natural equivalents weren't tough enough to do the job on their own, a more holistic approach to controlling insects came into vogue — integrated pest management.

According to its proponents, IPM is the most effective, eco-friendly way to deal with harmful insects. It combines complementary strategies, including sanitation, monitoring and eco-friendly pesticides.

Mark Puglisi, ACE, is the general manager of Greenleaf Organic Pest Management Inc, based in Los Angeles. His pest-control experts have more than 15 years of experience with IPM.

"IPM has been around for many years and is the responsible way to operate," he says. "IPM incorporates sanitation, mechanical control, inspection and other non-chemical means to control pests."

A typical IPM program decides whether any action should be taken — such as if insects become an economic threat. The insects are then identified, with care taken to monitor the balance between the beneficial and detrimental bugs.

The next step is to use specifically targeted chemicals such as pheromones, which will disrupt mating patterns, or mechanical means, such as traps.

Sometimes, however, that's not enough, and the only resort is to use insecticides. Only environmentally friendly insecticides are used, and as infrequently as possible.

A number of studies conducted in the U.S. and abroad have shown that botanical pesticides, when used properly, can be as effective as synthetic pesticides at killing a broad spectrum of pests both in domestic and agricultural settings.

Botanicals use essential oils from plants known to have natural insecticidal properties, such as chrysanthemum, garlic, sweet flag and clove. Not only do these natural avengers zap the bad bugs, they are also harmless to humans and the environment.

Many of the newer green pesticides have a unique mode of action that targets and blocks a key neurotransmitter receptor site.

"The neurotransmitter in insects is called octopamine; it is basically the insects' version of adrenaline," explains Gary Stamer of Chemtec Pest Control, based in Saddle Brook, N.J. "The botanicals block the octopamine, resulting in a shutdown of the insect's nervous system. Since only insects have this receptor, there is no harm to mammals, birds or fish."

But how can consumers be certain how green their "natural" pesticide is? Check with the Integrated Pest Management Institute of North America, which awards its Green Shield Certification (GSC) to services that use non-chemical approaches to pest control, and use approved pesticides only when necessary.

GSC helps consumers avoid being "greenwashed" by pest-control companies, because it provides a reliable and consistent set of tests and standards.

"Organic products have been around for a long time, but really did not work well in the beginning," said Puglisi. "New technology has changed that, and with proper training, IPM and listening more, we as an industry will continue to be truly the protectors of health with the services we provide."