Organic pesticides aren't necessarily green:

On a per-weight basis, all six of the pesticides had similar environmental impact factors (ranging from 8.7 to 47.2) with the organic variants being in the bottom half of this ranking.

When the data was converted into the environmental impact on a field use basis (pounds needed per acre), the organic pesticides did not fare so well. The mineral oil had by far the largest environmental impact factor, a whopping 280.2 rating; the next most damaging pesticide only garnered a 12.5 environmental impact factor. The fungus did better, but still ranked fourth out of six in terms of least environmental impact.

The authors conclude that, when compared to synthetic pesticides, the organic variants were not as effective because they also killed off a large number of the aphid's natural predators.

The paper cautions that those seeking to be kind to the environment should not fall for the simplistic belief that organic is environmentally friendly—a comprehensive review of pesticides is needed to determine which is truly best for a given use.

"The consumer demand for organic products is increasing partly because of a concern for the environment," said one author, Rebecca Hallett. "But it's too simplistic to say that because it's organic it's better for the environment. [...] It's a simplification that just doesn't work when it comes to minimizing environmental impact."