Are Organic Pesticides Safe?

Not automatically. "Organic" on a pesticide means its ingredients fit the rules of the National Organic Program. It doesn't mean the product is harmless. Some organic-approved insecticides, including spinosad and pyrethrins, are rated highly toxic to bees, and pyrethrins are highly toxic to fish. Some of those same products are low in toxicity to people, and others, like kaolin clay and the kurstaki strain of Bt, carry low risk to bees. The honest answer is that safety depends on the specific product, the organism you're worried about, and how and when you apply it.

Why "organic" doesn't mean non-toxic

The organic rules sort substances by origin first and by review second. The USDA explains that the standards generally allow natural substances and prohibit synthetic ones, with the National List making exceptions. USDA gives strychnine and arsenic as examples of natural toxic substances that are prohibited, which tells you the rules themselves don't treat natural as safe.

What survives that process is still designed to kill pests. NC State Extension's gardener handbook states: "All pesticides, natural or synthetic, are toxins designed to kill pests, and should be treated as poisons." Oregon State University makes the same point for home gardeners: "organic" does not mean pesticide-free, and no matter how natural, all pesticides should be used with care.

The Xerces Society, a pollinator conservation nonprofit, opens its fact sheet on organic-allowed pesticides with the plain version: pesticides allowed in organic agriculture can cause harm to bees and beneficial insects.

Bee toxicity, product by product

The table below comes from the Xerces Society's comparative overview of organic pesticides. The University of California's Bee Precaution Pesticide Ratings tool, which ranks products from I (most hazardous) to III, agrees on the broad picture: spinosad products rate I, while insecticidal soap rates III.

Spinosad

Spinosad is made by a soil bacterium and acts on the nervous system of insects that eat or touch it. The National Pesticide Information Center (NPIC) at Oregon State University describes it as low in toxicity to people and other mammals but "very highly toxic to bees." NPIC adds that evidence suggests it has little or no effect on honey bees and other beneficial insects after sprays have dried. That's the basis for the standard advice to spray when bees aren't flying and let it dry before they return. Xerces notes that granular bait formulations generally carry much lower exposure risk than sprays.

Pyrethrins

Pyrethrins come from chrysanthemum flowers. NPIC's pyrethrins fact sheet describes them as low in toxicity to people and other mammals, practically non-toxic to birds, highly toxic to honey bees, and highly to very highly toxic to fish. They break down quickly in sunlight. Xerces notes they are toxic to bees on direct contact, and recommends applying at night if you must spray during bloom. NPIC also notes that pyrethrin products are often mixed with another chemical to increase their effect, so read the full ingredient list, not just the headline active ingredient.

Neem and oils

Neem and horticultural oils sit in the middle of the Xerces ratings. The National List describes allowed horticultural oils as dormant, suffocating, and summer oils; a spray that works by coating insects doesn't distinguish pests from the beneficial insects it lands on. Neem has enough nuance to get its own page: does neem oil hurt bees?

Copper

Copper's main concern isn't bees; it's soil. Xerces warns that copper can accumulate in soils and that contaminated soils are difficult to remediate. The federal National List recognizes this directly: copper-based materials "must be used in a manner that minimizes accumulation in the soil." In a home garden where you grow tomatoes in the same beds year after year, that's worth taking seriously.

Organic versus synthetic: what research found

It's tempting to assume that any organic option is gentler than any synthetic one. At least one field study tested that assumption directly. Bahlai and colleagues (2010, PLOS ONE) compared organic-approved and newer synthetic insecticides for soybean aphid control. The organic options (a mineral oil and the fungus Beauveria bassiana) controlled aphids less effectively, had similar or greater negative effects on several natural enemies in lab tests, were more harmful to biological control organisms in field experiments, and had higher Environmental Impact Quotient scores at field rates.

The authors concluded that "generalizations based on chemical origin do not hold true in all cases." Keep the scope in mind: it's one crop, one pest, and a small set of products, so it doesn't prove organic pesticides are generally worse. What it does show is that "organic" isn't a reliable shortcut for "lower impact."

The EPA's view is more favorable to the category as a whole. Its page on biopesticides says they are "usually inherently less toxic than conventional pesticides," often affect only the target pest, and often decompose quickly. Both things can be true: many naturally derived products are lower risk, and some specific organic products are high risk to specific organisms.

Using organic pesticides with less harm

• Make spraying the last step, not the first. Certified organic farms are required to work this way. 7 CFR 205.206 puts rotation, sanitation, cultural practices, and mechanical or biological controls ahead of pest control substances, which are used only when those practices are insufficient. See no-spray pest management and row covers for pest control.
• Time it around bees. Xerces recommends applying in the evening or at night, especially for products that break down quickly. Avoid spraying open flowers.
• Pick the lowest-risk product that will work. In the Xerces ratings, Bt kurstaki rates low for bees while spinosad rates high, and insecticidal soap rates lower than oils or pyrethrins. Match the product to the pest first, then choose the gentlest option that fits.
• Read the label, every time. The EPA notes that using a pesticide in a manner inconsistent with its labeling violates federal law. That applies to organic products exactly as it does to synthetic ones.
• Don't read the organic claim as a safety claim. The EPA's "For Organic Production" label means the ingredients and uses meet National Organic Program criteria. The OMRI Listed seal is similar. Neither is a toxicity rating.

For how the organic label works more broadly, and what OMRI, "natural," and non-GMO do and don't promise, see Organic Gardening, Actually. If you're choosing products to protect pollinators, beneficial insects in the garden covers who you're trying to protect.