- Author: Jeanette Alosi
The decline in numbers of European honeybees, bumblebees and other native pollinators has been well documented for over a decade. Research exploring pollinator decline began in earnest in 2006 when Colony Collapse Disorder, affecting honeybees, first appeared. In 2006 and 2007 managed honeybee colonies experienced a loss rate of over 30 percent. There was great concern that the loss of pollinating honeybees could negatively affect agricultural production including our local almond crop. Although managed honeybee colonies rebounded (thanks to improvements in hive management), hive losses from April 2018 to April 2019 reached 40%, the highest loss since monitoring began, primarily due to reduced effectiveness of Varroa mite control materials.
Neonics are a nicotine-derived class of pesticides developed for use on both farm crops and landscape plants. Approved by the EPA in the 1990's, this group of neurotoxins are the most commonly applied group of insecticides in the world.
No direct link has been found between neonics and the Colony Collapse Disorder of honeybees. Although not clearly understood, neonics may weaken the honeybee immune system, thus making the bees more susceptible to pathogens and diseases. Research has also found that bumblebees and solitary bees are affected differently than honeybees. A study at Worcester Polytechnic Institute in Massachusetts discovered that queen and male bumblebees suffer much higher rates of mortality compared to that of worker bees. This negatively affects the ability to form new colonies.
Neonics are long lasting; they can persist in the soil for months, but can last years in woody plants. When used to protect corn and other seeds, they can remain in the soil to be absorbed later by other untreated plants.
Because many products approved for home and garden use can be legally applied at rates significantly higher than the rates approved for agricultural crops, home gardeners may unwittingly be exposing pollinators to toxic levels of pesticide. Neonic pesticides found in common home and garden products include imidacloprid, clothianidin, thiamethoxam, acetamiprid, and dinotefuran.
The Butte County UC Master Gardeners are part of the University of California Cooperative Extension (UCCE) system, serving our community in a variety of ways, including 4H, farm advisors, and nutrition and physical activity programs. Our mission is to enhance local quality of life by bringing practical, scientifically-based knowledge directly to our community. For more information on UCCE Butte County Master Gardeners and their upcoming events, and for help with gardening in our area, visit https://ucanr.edu/sites/bcmg/. If you have a gardening question or problem, call our Hotline at (530) 538-7201 or email mgbutte@ucanr.edu.
Examples of neonicotinoid ingredients found in common garden insecticides: |
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By Jeanette Alosi, Butte County Master Gardener, December 19, 2014
The role of chemical pesticides in the decline of pollinators has been widely studied. Eric Mussen, a University of California Cooperative Extension expert on beekeeping (apiculturist), reported that researchers have found nearly 150 pesticide residues in samples of adult bees, pollen, and beeswax taken from beehives. Among these residues, which are thought to be involved in colony decline and loss of native pollinators, are limited amounts of neonicotinoid insecticides (neonics). A mass die-off of bumble bees in Oregon has been attributed to a mis-application of a neonicotinoid on linden trees. Although no direct link has been found between the neonics and what is known as Colony Collapse Disorder of honeybees, it is believed that these pesticides weaken the honeybee immune system, thus making the bees more susceptible to pathogens and diseases.
The neonics have several characteristics that are attracting attention. They are systemic pesticides, meaning they are absorbed into the plant tissue. Systemic pesticides can be applied in a number of ways; by drenching the soil; injecting directly into trees; used as a spray; and even applied as a seed coating. As these pesticides are translocated throughout the plant tissues, pollen and nectar become toxic. Pollinators that visit flowering plants to collect pollen and nectar are then exposed to the pesticide. Research has found that even small levels of neonics affect the ability of bees to navigate and impair their ability to detect odors. These are both important factors in their ability to forage for food.
Neonics are long-lasting and have been found to persist in soils for months and even up to six years in woody plants. Untreated plants can also absorb these chemicals from soil residues from previous applications. This is of particular concern because they are used constantly to coat corn and other seeds, leading to a cycle of soil contamination.
Because many products approved for home and garden use can be legally applied at rates significantly higher than the rates approved for agricultural crops, home gardeners may unwittingly be exposing pollinators to toxic levels of pesticides. Neonics found in common home and garden products include imidacloprid, clothianidin, thiamethoxam, acetamiprid, and dinotefuran.
What can you do to help? Avoid using systemic neonic products in your garden by checking the active ingredients on the label. Ask local nurseries if plants or seeds they sell are treated with a neonic product. Several home and garden retailers have already agreed to eliminate neonic-treated plants from their nurseries. When applying a fertilizer, avoid fertilizer-pesticide combinations because many of them contain neonics. If pesticide use is warranted to control worm pests, turn to one of the organic pesticides such as Bt. Most importantly, practice Integrated Pest Management or IPM techniques to control garden pests (see http://www.ipm.ucdavis.edu/). Chemical pesticides can negatively affect all insects, including ladybugs and other beneficial predators that keep destructive pests such as aphids under control.
Create a pollinator-friendly garden by planting patches of pesticide-free flowering plants. The goal is to provide food sources for pollinators throughout the year. The Xerces Society is a great resource for more information on the dangers of neonics and how to create a pollinator friendly garden. http://www.xerces.org.
Examples of neonicotinoid ingredients found in common garden insecticides: |
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