Good Fruit Grower

May 1

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Page 42 of 55 GOOD FRUIT GROWER MAY 1, 2014 43 s a plant pathologist who makes recommendations to tree fruit growers throughout New York and neighboring states, I am very concerned about evidence that some fungicides are exacerbat- ing bee mortality as reported in the March 15 issue of Good Fruit Grower. I would like to make extension recommendations that will help to minimize threats to bees, but we need much better information from the bee research community before anyone can formulate management changes that will protect both the bees and our tree fruit crops. Bee researchers and beekeepers who suggest that growers should simply avoid spraying fungicides during bloom when bees are foraging display an extreme naiveté about crop protec- tion. In nonarid environments, most fruit growers will apply fungicides during bloom in most years because failure to do so could create an outcome just as disastrous has having no bees: the entire crop could be lost to fungal diseases. Fungicide applications during bloom cannot always be made at night (to avoid foraging bees) due to constraints of weather and acreage to be covered. Thus, fruit growers need to apply fungicides during bloom just as much as beekeepers need to introduce pesticides into their hives to control Varroa mites. Which fungicides? Rather than blaming fungicides as a category and then suggesting that all fungicides be avoided during bloom, we need to know exactly which fungicides contribute to bee problems and at what application timings. By my count, we currently have at least 25 active ingredients labeled for use as fungicides for apples during bloom, and there probably is about the same number available for stone fruits. However, the recent article in Good Fruit Grower mentions only chlorothalonil, GOOD POINT Dr. Dave Rosenberger, Cornell University Concerns about fungicides and bees Crops must be protected as well as bees. 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"The synergistic effect of pesticides in hives" appeared in the March 15, 2014 issue. Pollination I n many ways, honeybees are the canaries in the coal mine, the critters that die fi rst when the air gets bad. For the last several years, people have been in a frenzy over the high mortality of honeybee hives. Not only are they concerned about bees, but they're concerned that pollination of food crops will be threatened. But it's not one thing in the environment—like methane in the coal mine—that threatens honeybees. It's a combination of things that don't just add together, but multiply. One plus one doesn't always equal two; it may equal 2,000. That's called synergism. Researchers at Pennsylvania State Uni- versity, including entomologists Drs. Jim and Maryann Frazier and Chris Mullin, have found that, in combination, four commonly used pesticides kill honeybee larvae in the hive. More concerning is that one of these is chlorothalonil, a fungicide commonly used in fruit and vegetable production. And even more concerning, in Mullin's view, is that a supposedly inert chemi- cal—N-methyl-2-pyrrolidone (NMP), commonly used in formulating pesticides—is itself highly toxic to bee larvae. In a telephone interview with Good Fruit Grower, Mullin said that so-called inert ingredients are widely used, don't have to be named on pesticide labels used in the formulation, and are often trade secrets that even government agencies don't disclose. "There are about a thousand active ingredients that are pesticides," he said. "There are over 2,000 substances that are classifi ed inert." These can be used in formulating everything from personal care products to pharmaceutical drugs to pesticides. He hopes the Penn State research will make the U.S. Environmental Protection Agency more proactive in looking at inert ingredients and the effects of mixtures of pesticides. Some of the silicone surfactants now being used in pesticide spray tank mixes greatly increase penetration, changing the lethality of the pesticides. It's a two-edged sword, since a surfactant can reduce the amount of active ingredient that needs to be used, which is usually considered a positive thing. Bee-havior The day-to-day behavior of honeybees makes them—and the brood they feed—vul- nerable to toxic materials. They fl y through air, picking up particles on the hairs of their body—then land and sweep up pollen to carry back to the hive to provide the protein that bee larvae need to develop. What gets into those pollen baskets on their legs is a mixture of things, since pesticides can be in or on the pollen as well as the fl owers they visit. The team's previous research showed that forager bees bring back to the hive an average of six different pesticides on the pollen they collect. Nurse bees use this pollen to make beebread, which they then feed to honeybee larvae. Change needed at EPA The team's research was published in January in the online science journal PLoS ONE and further publicized in a Penn State University article. "We found that four of the pesticides most commonly found in beehives kill bee larvae," Jim Frazier reported in the article. "We also found that the negative effects of these pesticides are sometimes greater when the pesticides occur in combinations within the hive. Since pesticide safety is judged almost entirely on adult honeybee sensitivity to individual pesticides and also does not consider mixtures of pesticides, the risk assessment process that the Environmental Protection Agency uses should be changed." Interestingly, however, two of the pesticides studied (fl uvalinate and coumaphos) are not crop protection chemicals, but miticides placed in the hives by beekeepers themselves to control Varroa mites. The mites, which came to the United States about 30 years ago, have had an overwhelmingly negative impact on bees and beekeepers. They feed on and kill bees directly or through the viruses and diseases they carry. They are now thought to play a key role in colony collapse disorder. The other two pesticides in the study were chloro thal onil (sold under many brand names including Bravo) and chlorpyrifos (sold under many names including Lorsban). Chlorothalonil has been widely used for 50 years because it is broadly effec- tive and diseases do not develop resistance to it. It is this multisite action that probably makes it more toxic to bees, Mullin said. Among the four pesticides, honeybee larvae were most sensitive to chlorothalonil. Pesticides may directly poison honeybee larvae or they may indirectly kill them by disrupting the fungi that are essential for nurse bees to process pollen into beebread, Mullin stated in the article. "Chronic exposure to pesticides during the early life stage of honeybees may contribute to their inadequate nutrition or direct poisoning with a resulting impact on the survival and development of the entire bee brood," he said. Mullin's advice to growers is to avoid applying fungicides during bloom when bees are foraging. Beekeepers are also attempting to shift away from the miticides they are now using to amitraz (sold as Apivar), a miticide that has, so far, not shown synergis- tic effects with other chem- icals. It has been approved for use in some states under Section 18 permits from the Environmental Protection Agency. • The synergistic effect of pesticides in hives How bad things in the environment gang up and kill bees. By Richard Lehnert Causes of honeybee colony losses, as reported by domestic-market beekeepers These nine reasons for honeybee overwintering losses were self-reported by beekeepers in annual surveys conducted by the USDA, the Apiary Inspectors of America, and online surveys. Data summarized by Dennis vanEngelsdorp and colleagues. Chart was created by Dr. Kristine Smith and colleagues at EcoHealth Alliance, New York City, and presented in their paper, Pathogens, Pests and Economics: Drivers of Honey Bee Colony Declines and Losses. CCD* Poor queens Mites † Starvation Nosema Viruses Pesticides Weak in the fall ‡ Weather 40 30 20 10 0 Percent of responses for each colony loss factor 2008 2009 2010 2011 Years of overwintering losses NOTE: Respondents had the option to report multiple causes for colony loss each year, each cause is reported as percent of total responses given. Double dagger: Includes colonies reported to have been weak in the fall and usual overwintering losses. Dagger: Primarily V. destructor; however in some years reported as "invertebrate pests" including tracheal mites (Acarapis woodi) and the small hive beetle (Aethina tumida).%WXIVMGOWHI½RIH only by the loss of a colony with the absence of dead bees—and thus true cases of CCD—are likiely to be overestimated in all years. "Four of the pesticides most commonly found in beehives kill bee larvae." —Dr. Jim Frazier PLAY scan to watch Dr. Maryann Frazier 8 MARCH 15, 2014 GOOD FRUIT GROWER Watch: How growers can protect honeybees.

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