When it became abundantly clear, the monarch population was in decline private citizens, government agencies, and conservation groups launched an international effort to save this spectacularly beautiful butterfly. One of the problems facing the monarch is a lack of the milkweed. The milkweed is the monarch’s only known host. For quite some time, thousands of us have been trying to remedy this problem by planting native milkweeds in our yards. In response to the high demand for milkweeds, commercial nurseries expanded the propagation and marketing of these important caterpillar plants. However, a recent study conducted by the Xerces Society and the University of Nevada found many of these plants are contaminated with chemicals that are potentially harmful to monarchs.
The researchers tested the foliage of 235 milkweed plants sold at 33 nurseries scattered across the United States. The researchers were trying to determine if any of these plants harbored chemicals that might be harmful to monarch caterpillars.
The study revealed the plants were contaminated with 61 different pesticides. As many as 28 different pesticides were found in or on individual plants. Another startling discovery was an average of 12.2 pesticides was found per plant.
Ironically, plants advertised as “wildlife friendly” were not contaminated with fewer pesticides. Instead, many actually harbored more of the deadly chemicals than those not so labelled. In fact, with respect to one pesticide, milkweed plants that were supposedly sold as being wildlife friendly had a greater chance of being contaminated with a dose of it that exceeded the known sub-lethal concentration.
Matt Forister, a professor at the University of Nevada, Reno expressed his feelings regarding these alarming findings this manner, “In many ways, they are as contaminated or worse than plants growing on the edges of agricultural fields. That was quite a surprise to me.”
To date, the potential impacts of only 9 of the 61 chemicals on the monarch are known. However, the scientists pointed out that 38 percent of the samples contained high enough concentrations of the chemicals that could affect the monarch’s ability to eat and migrate.
Where does that leave those of us that purchase these plants? The researchers recommend that we encourage the nurseries where we buy milkweed plants to sell only pesticide free plants.
In addition, Aimee Code, Pesticide Program Director at the Xerces Society went on to say, “It’s important to keep gardening for pollinators for the long term. Just take steps to reduce pesticide exposure: cover new plants the first year, water heavily, discard the soil before planting, as it may be contaminated, and avoid pesticide use.”