Things have changed since the days when pesticides like DDT, lead arsenate and chlordane were used indiscriminately without knowledge of how damaging they were to human health and the environment. Scientists eventually came to understand the harmful long-range effects of these very toxic and persistent chemicals. This led to their eventual discontinuation, despite the protests of growers and gardeners.
They were replaced with newer pesticides that were believed to be safe until their harmful effects were also revealed. This has happened repeatedly over the years, each time leaving gardeners worrying if there would be a new chemical that would be as effective as the older, tried and true materials. Fortunately, researchers are constantly working to develop new, safer chemicals for pest management.
One “newer” type of systemic insecticides are the neonicotinoids. Gardeners have found them to be very useful chemical tools. Imidacloprid, one of the neconictinoids, was hailed for its effectiveness and lower toxicity in birds and mammals. Other neonicotinoids include acetamiprid, clothianidin, nitenpyram, nithiazine, thiacloprid, and thiamethoxam. Believed to be a safe option, the popularity of imidacloprid and the other neonicotinoids soared, and they became widely used throughout the world on crops, turf, trees and other landscape plants.
In 2006, it was noted that honey bee colonies were disappearing at an alarming rate and have continued to decline since then. Millions of beehives have been lost. Native bee populations have drastically diminished.
Honey bees and native bees are crucial to the production of many food crops. Researchers have been frantically trying to discover the cause or causes of the alarming honey bee decline. Those studying the problem point to the Varroa mite, pesticides, pathogens, loss of bee habitat, and poor hive management as the major contributing factors. Read more in the WSU Extension Fact Sheet “Neonictinoid Pesticides and Honey Bees” at cru.cahe.wsu.edu/CEPublications/FS122E/FS122E.pdf.
Serious concerns arose because the increased widespread use of neonicotinoids seemed to correspond with the honey bee decline. Despite numerous studies around the world, research has yet to point to neonicotinoids as a definitive major contributor to the bee decline problem. However, evidence does suggest continued research is needed to investigate their possible contribution to the problem. Until more is known, researchers urge care when using neonicotinoids on garden and landscape plants.
While not proven to be the cause of the problem, many U.S. stores intend to phase out home garden pesticides containing neonicotinoids by 2019. This includes Walmart, True Value, Lowe’s, Home Depot and others. I am hoping that by then there will be new chemicals available to home gardeners to replace the neonicotinoids and still effectively control pests in the yard and garden.
One new group of chemicals on the horizon are the anthranilic diamides. These low toxicity chemicals have been found to be as effective as the neonicotinoids and the pyrethroids, but they are more expensive to manufacture. Anthranilic diamides kill insects by causing the uncontrolled release of calcium from muscle cells and interfering with muscle contraction within the insect body. Cyantraniliprole, an anthranilic diamide, is a broad spectrum systemic insecticide that kills sucking and chewing insects, but appears to have no negative effects on bees or wasps.
Perhaps cyantraniliprole will be a good replacement for imidacloprid. We can only hope that it or other low toxicity, bee-friendly materials will become available for home garden use very soon.
Marianne C. Ophardt is a retired horticulturist for Washington State University Benton County Extension.