The use of medicines for plants, and, in particular, insecticides is a complicated one and, as environmentalists and plant lovers, we struggle daily making decisions for the benefit of the plants, our staff, our customers, and the environment.
The current populist target is a group of insecticides known as neonicotinoids or "neonics." Neonics are chemically similar to, and have the same mode of action as, the organic pesticide nicotine. Since neonics' purpose is to kill insects, it may come as no surprise that when used incorrectly they are damaging to European honeybees.
The current movement to ban neonics has reached a fever pitch, so we're weighing in on the subject.
First, let's understand why we have honeybees. Like kudzu, honeybees were intentionally brought into the US for human benefit. European honeybees (Apis mellifera) were actually native to Africa before migrating to Europe. They were brought to America from Europe via three different human introductions...one in the early 1600s and two in the mid-1800s. Actually, on a much larger time scale, a long-extinct species of honeybee (Apis neartica) was native to the Americas around 14 million years ago (Miocene epoch).
Fast-forward back to the present day. If a business owner grew a crop of plants which did not attract honeybees, like many grasses or wind pollinated plants and these plants were attacked by a deadly pest...what would be the available options?
In most cases, the overall least toxic option are neonics, which are actually one of the safest pesticides for vertebrates currently on the market. All pesticides are rated by the lethal dose (LD50) required to kill 50% of the population of a test subject (based on milligrams of pesticide per kilogram of body weight). The most common neonic is Imidacloprid, which has an oral LD50 of 450...half as toxic as Aspirin (LD50 of 200) and 45 times less toxic than organic nicotine (LD50 of 10).
Another treatment option would be the predecessor of neonics...organophosphates, which have a much higher toxicity to vertebrates. There are currently 32 commonly used insecticides labeled for use in the US with an equal or greater toxicity to European honeybees than neonics. Six are carbamates, including the very popular homeowner insecticide Sevin (Carbaryl); twenty-five are organophosphates and four are pyrethroids.
A third treatment option would be an organic...if one is available, efficacious, labeled appropriately, and not more toxic that the other options. FYI, according to studies by the Organic Crop Improvement Association, over half of natural/organic pesticides are also carcinogenic, so natural/organic doesn't necessarily mean safe.
Another scenario would be growing crops of endangered native plants that are attacked by a pathogen. In this case, a neonic is the only viable option. What takes priority...the endangered US native plant or the risk of mildly affecting the non-native honeybee population if the insecticide is misused?
One final point to ponder. Human medicines are now regularly found in drinking water with over 50 different medicines found in the water supply of some municipalities. Research has shown that the diabetes drug Glucophage (Metformin) alters the sex habits of native fish, and native birds that drink water with Prozac (Fluoxetine) lose interest in eating and mating. Is a ban of all 50 medicines the answer? The issues of medicines and their effect on the environment are much more widespread that just their effect on European honeybees.
All medicines, whether for plants, humans, or other animals are created to be harmful to another organism...that's why they work. So, do we ban all medicines or teach people how to responsibly use them, while continuing to look for safer alternatives? How easy it would be if each decision we face in life was black and white instead of shades of grey.
These are the scenarios growers face on a daily basis. It pains us to have to use any medicines but that's our reality, although we currently do not use neonics on flowering plants. All we can do is make responsible and logical choices in each situation as to what is the safest, most environmentally and humanly friendly method to keep plants healthy. We have honeybee hives in the gardens and eat the honey at every opportunity. That's how important this issue is to us and how confident we are that we are responsibly using plant medicines in the nursery and garden.
The research on neonics continues, with more science emerging daily, and we encourage reading and studying from both sides of this dilemma. It is interesting that research coming from the EU has resulted in scaling back their initial neonic ban. This sadly comes too late for many of their prestigious botanic gardens. When visiting the EU last year, staff bemoaned privately to me that they had lost up to 50% of their plant collections due to these pesticide bans. Some of the plants lost were one-of-a-kind, irreplaceable collections...many extinct in the wild. It's a balancing act and decisions are made with careful and long-studied review.
In our humble opinion, choosing which medicines we use for our plants and being the best stewards of the environment must be based on individual circumstances and ever evolving scientific research. The latest report from the EPA on neonics is here.