Systemic Pesticide Chemicals Can’t be Washed Off Fruits and Vegetables

 (Organic Slant) Washing or peeling fruits and vegetables before you eat them won’t protect you from systemic pesticides. Systemic pesticides are in the plant, not on it. When we make the plant itself poisonous to predators, one has to wonder what (or who) else it’s poisoning.

In conventional food production systems, not all pesticides remain on a plant’s exterior. Systemic pesticides are chemicals that are actually absorbed by a plant when applied to seeds, soil or leaves. The chemicals then circulate through the plant’s tissues, killing the insects that feed on them.

Most pesticides are ‘residual’; that is, they cling to the surface of a plant and remain active for a certain amount of time. Bacillus thuringiensis subsp. kurstaki; also known as Bt—an organically approved naturally occurring soil organism that’s deadly to caterpillar pests—is a good example. You spray it on a plant being eaten by caterpillars and the caterpillars currently feeding on the sprayed leaves die, and so do any new ones that show up to feed for a while. How long that ‘while’ lasts depends on variables like temperature, rain, and sunlight.

‘Systemic’ pesticides are taken up inside the plant, typically through the root system, so that every part of the plant then contains the chemical. As you can imagine, systemics on food crops are an especially bad idea. In fact, in one of their very first uses, the string beans they were “protecting” became as poisonous to people as the attacking bean beetles.

Merit is the most widely used systemic pesticide, and the active ingredient in Merit is the chemical most implicated by researchers in the Colony Collapse Disorder decimating honeybee hives around the world. Growers use Merit to protect their plants, bees ingest the chemical when they collect pollen from those plants, and boom—the bees are poisoned because the chemical is in every part of the plant, including the pollen. And this isn’t specific to just Merit; its just one example of how these types of pesticides can have a profound and deadly impact on non-target organisms like pollinators.

Use of these pesticides on food crops began in 1998, and has steadily increased during the past 10 years. Unlike with traditional insecticides, you can’t wash or peel off systemic pesticide residues because they’re in the plant’s tissues, not on their exteriors.

The four main systemics used on food crops (listed below) are members of the nitroguanidine/ neonicotinoid group of chemicals.

Imidacloprid can be applied to many vegetables (including tomatoes and leafy greens) right up to the day they’re harvested.

Thiamethoxam was first approved as a seed treatment for corn in 2002, and thiamethoxam products that are applied to the soil have since been approved for use on most vegetable and fruit crops. See a photo of seed corn treated with this chemical.

Clothianidin is used as a seed treatment on canola, cereals, corn and sugar beets, and as a soil treatment for potatoes.

Dinotefuran can be applied to soil or sprayed on leafy greens, potatoes and cucumber family crops.

When the Pesticide Action Network reviewed the results of pesticide residue tests conducted by the U.S. Department of Agriculture from 1999 to 2007, numerous samples contained residues of these systemic pesticides. For example, 74 percent of conventionally grown fresh lettuce and 70 percent of broccoli samples showed imidacloprid residues. Clothianidin was found in potatoes, thiamethoxam showed up in strawberries and sweet peppers, and some collard green samples were laced with dinotefuran.

The U.S. Environmental Protection Agency (EPA) has launched a comprehensive review of the environmental safety of imidacloprid, but we won’t have results until 2014! In the meantime, the state of California initiated its own reevaluation (currently ongoing) of all four systemics in February 2009. Among its reasons, California’s Department of Pesticide Regulation cited reports of eucalyptus nectar and pollen with imidacloprid levels up to 550 parts per billion — nearly three times the 185 parts per billion needed to kill honeybees. And deadly levels of these systemic poisons are even showing up in leaf guttation drops (water droplets that plants sometimes exude). According to a 2009 report in the Journal of Economic Entomology, “When bees consume guttation drops, collected from plants grown from neonicotinoid-coated seeds, they encounter death within a few minutes.”