Most people have heard about the decline in honey bees during the last several years. Are there things that landscape professionals or home gardeners can do to help?
Better Nutrition, Fewer Pesticides
(c) Kathy Keatley Garvey
The actual cause of the honey bee decline is still uncertain. What is known is that a number of factors are probably involved. For instance, honey bees are in their most robust condition and able to best contend with stresses when they are well fed. In addition to water, honey bees require nectar sources for carbohydrates and a varied mix of pollens to provide proteins, lipids, vitamins, minerals, sterols, antioxidants, and other nutrients.
Pesticides can also be involved in bee decline, especially when applied to plants when they are in bloom and bees are foraging. Many insecticides are highly toxic to bees including virtually all organophosphates, carbamates, and pyrethroid materials.Drought, flooding, and conversion of former foraging grounds into large agricultural monocultures, highways, airports, developments, and so forth have led to honey bee malnutrition in many locations. Also, in the last 20 years beekeepers have been encountering a series of previously exotic pests that invade the hive and kill bees, such as the varroa mite; new honey bee diseases, including Nosema ceranae; and many RNA viruses.
If not killed in the field, pollen-foraging bees can collect residue-contaminated pollens and bring them back to the hive for immediate consumption or long-term storage. There are serious concerns over the chronic, sublethal effects of these residues on the physiology of immature and adult bees.
(c) Kathy Keatley Garvey
A newer class of insecticides, the nicotinoids, which include imidacloprid, clothianidin, and dinotefuran, also pose hazards for honey bees. These products are systemic materials that move through the plant and will be included in nectar and pollen of flowers when they bloom. Although the neonicotinoid residues may not kill bees immediately, they may have sublethal effects, such as the suppression of immune and detoxification systems, that cause bees to be more sensitive to other stresses.
Use Plants and Pesticides Wisely
There are several ways landscape managers can help protect bees. When designing
or replanting a landscape, consider honey bees and other pollinators in your plan. Include plants honey bees prefer, and try to ensure that several bee-friendly plants will be blooming throughout the year.
Also, avoid applying highly toxic insecticides, especially when plants are in bloom. Be aware that neonicotinoids tend to be stable compounds that can remain in the soil and in plants for months and still be present when the plants bloom.
Even when plants aren’t in bloom, use nonchemical management methods or pesticides with little or low toxicity to bees whenever possible, as pesticides may leave toxic residues or there may be flowering weeds or other blooms nearby.
For information about relative toxicity of pesticides to bees, consult How to Reduce Bee Poisoning from Pesticides at http://www.ipm.ucdavis.edu/PDF/PMG/pnw591.pdf. Toxicity of many landscape and garden pesticides to bees is also listed in the UC IPM landscape and garden pesticide active ingredient database at http://www.ipm.ucdavis.edu/PMG/menu.pesticides.php.
Many thanks to the University of California, Agriculture and Natural Resources for this wonderful article. Specifically,
—Eric Mussen, Entomology,
UC Davis, firstname.lastname@example.org
Special thanks to Kathy Keatley Garvey for the beautiful photos in this article. Kathy works at the University of California, Davis, with Eric Mussen, Extension apiculturist in the Department of Entomology and Nematology