Issue link: https://read.dmtmag.com/i/275392
www.goodfruit.com GOOD FRUIT GROWER MARCH 15, 2014 25 A TOXIC WORLD coumaphos, and amitraz. While they can't make money on dead bees, the very chemicals they use for Varroa mite are often found in commercial honeybee wax and pollen. WSU research shows that these Varroa mite pesticide residues—often the highest of all pesticides detected in the wax and pollen—stay in the colony for long periods of time. While there are alternative means to control Varroa mite, such as biological pesticides, mite-tolerant breed- ing stock, and mechanical control, the methods are time consuming and not always as effective. Another beekeeper-induced stress on honeybees is the intense management practice of supplemental feed- ing. To ensure strong colonies for almond pollination in late winter, beekeepers in some regions feed thousands of colonies pollen substitute and sugar syrup. Studies show this feedlot feeding may reduce the bees' ability to detoxify pesticides and make them more susceptible to some pesticides. U.S. Department of Agriculture scientists have found a host of pesticides and chemicals in bees' wax in colo- nies across the country, according to Lawrence. He said that some believe surfactants brought back to the colony may be more detrimental than pesticides. Pathogens are also responsible for bee death and decline, he said. Pesticides to control Varroa mite and some neonicotinoids are believed to make bees more susceptible to diseases that in the past were not a prob- lem. Black queen virus is an example of a disease that has fl ared up in California bee colonies. Neonicotinoids Neonicotinoid pesticides have become one of the fastest growing classes of pesticides used in agriculture as well as in home and garden products because they have low mammalian toxicity and stay confi ned within the plant, working systemically. "They're relatively safe for use around people, animals, and the environment and are considered good products from an environmen- tal and safety perspective," he said. More than 465 neconicotinoid products are approved in Washington State, with 150 approved for home and garden use, according to Lawrence. But their systemic nature poses a problem with bees. "The pesticide moves throughout the plant and is in the plant's phloem, xylem, and even in the nectar," he said. In lab experiments, scientists have found that some neonicotinoids are lethal or sublethal to bees, depending on exposure. Dust from seeds treated with neo nico tinoids can have an acute effect on bees, and spraying neonicotinoids when bees are foraging will also result in quick death. However, the bigger concerns are the sublethal effects from neonicotinoids, he said. "There is growing concern for chronic exposure through nectar, pollen, and water picked up and carried back to the hive by foraging bees," stated Lawrence. Sublethal effects attributed to neonicoti- noids are impaired learning, altered for- aging and motor activity, and memory loss. "Neonicotinoids are part of the over- all problem—they do have a negative effect on honeybees—but they are not the sole problem," he said. "It's not any one thing that's responsible for honeybee decline." What's needed to stop the declining bee populations? He recommended that tree fruit growers avoid spraying during bloom and be more conscious about bees and how to protect them. Also, more research dollars are needed to better understand the interactions of various stresses on bees and to develop new products that have minimal impact on honeybees and other pollinators. But what bees really need, he said, are more fl owers. Bees have lost habitat and diversity from urban sprawl and monoculture practices of growing one crop in large blocks. "Bees need fl oral diversity to supply nutrients and stimulus. If we want to solve the honeybee problem, we need to plant more fl owers." • "Neonicotinoids are part of the overall problem— they do have a negative effect on honeybees—but they are not the sole problem." —Dr. Timothy Lawrence NEONICS WEAKEN bees' immune system I talian scientists believe neonicotinoid pesticides threaten honeybees by suppressing the bees' immune systems. Recent research in Italy discovered that neonicotinoids weaken the immune systems of bees by suppressing enzymes that help them resist viruses. This suppression allows even a minor viral infection to become fatal. According to European Fruit Magazine's December 2013, issue, scientists found that deformed wing virus infection levels rose strongly in bees that had been exposed to fi eld rate concentrations of neon- icotinoids. The Varroa mite was shown to be a vector in spreading deformed wing virus, a disease that causes the bees' wings to shrivel. "This transmitted virus in combination with the reduced resistance was fatal for the bees and is most likely the reason that bee colonies die in large numbers in the autumn," stated the magazine. "Bee colonies that are weakened by the time winter starts do not survive the winter." The European Commission restricted the use of three neonicotinoids (clothianidin, imidacloprid, and thiametoxam) last December for a period of two years, citing pesticide effects found in a scientifi c report of the European Food Safety Authority. The ban applies to seed treatment, soil application, and foliar treatment on plant and cereal crops attractive to bees. For European environmental groups, the Italian study may prompt new grassroots efforts to ban neonicotinoid use on all crops. The U.S. Environmental Protection Agency recently stated that their scientifi c conclusions are sim- ilar to those expressed in the European report with regard to the potential for acute effects and uncer- tainty about chronic risk. However, the EPA is mandated to consider risk management, something the European report does not address. In the United States, a coalition of beekeepers and environmental and food groups has sued the EPA for failing to protect pollinators. —M. Hansen PHOTOS BY MELISSA HANSEN PLAY goodfruit.com/media scan to watch Timothy Lawrence Watch an interview with Dr. Lawrence: