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The Landsculptor – March 2016 9 CONCOLOR FIR & RHIZOSPHAERA NEEDLECAST POLLINATORS AND PESTICIDES IN MICHIGAN LANDSCAPES The Plant Doctor’s LANDSCAPE TIPS By David L. Roberts, Ph.D., Senior Academic Specialist, College of Agriculture and Natural Resources, Michigan State University www.landscape.org Photo 1: A bee “working over” some Spirea flowers in a nursery in western Michigan. Routine sprays of pesticides to control various pests and diseases could adversely affect the bee populations in this fruit, vegetable and field crop production area. INTRODUCTION: Higher plants reproduce by producing flowers (recall your Plant Anatomy 101 course) consisting of, among a variety of parts, stamens that produce pollen that fertilize the pistils in flowers. The resulting fruits, nuts and seeds are important for Life on Planet Earth. Humans are dependent upon many of these plants and their products. Plants may be self-pollinated or they may be cross-pollinated by a variety of manners, including wind and physical transmission by insects (bees, flies, beetles butterflies, etc.) and animals (bats, hummingbirds, etc.). Bees represent a significant component of the pollination effort (Photo 1). Bees pick up and disseminate pollen as they feed on a flower’s nectar. Although there are over 4,000 species of bees in North America, honey bees, which are native to Europe, are especially important for pollinating many of our valuable food crops. Some of those food crops are dependent upon bee pollination including orchard fruits, berries, many vegetables and many field crops. Colony Collapse Disorder (CCD): For more than 10 years, bee populations have been in an overall steady decline. During some years, bee populations have declined severely. For example, during a one-year period from 2014-2015, honey bee populations were reported to have declined by 42% in the U.S., causing justifiable alarm to many agricultural producers, scientists and environmentalists alike. Native bee populations have also been reported to have declined. The decline has been blamed on many things including loss of habitat, various bee diseases and pests (example: Varroa mites, which can attack bee colonies), pesticides and even cell phones/towers. Some scientists believe that combinations of certain stressors such as bee diseases/pests and pesticides can stress colonies, making them more susceptible to winter kill. Continued on page 10 “If bees disappeared from the face of the earth, mankind would only have four years to live.” - Albert Einstein The cause of bee decline is one of the more controversial topics in science and among agribusiness and the general public at this time, even rivaling the extreme controversy surrounding the 2016 U.S. Presidential Elections. POLLINATORS, PESTICIDES AND RESEARCH: Because bees are insects, it stands to reason that insecticides could cause harm to these and other beneficial insects. And as with tobacco companies, who denied adverse effects of smoking upon human health, it also seems logical that certain entities will decry harmful effects of pesticides upon bees. Example: “Where’s the proof?!?!” Following are some examples of harmful effects of pesticides upon bee populations; this information gleaned from research: Pesticides can have direct lethal effects on bees—when flowers are sprayed with insecticides or when insecticides are found in the nectar or pollen of plants. Pesticides may also cause sub- lethal effects; bees with low-dose exposure to insecticides may not find their way back to their hives or they may not be able to feed their larval offspring or they may distribute pesticide-tainted food to their larvae. Affected bees may have a compromised immune system that can then make them more susceptible to attack by various pests and diseases. Pesticides vary tremendously in their toxicity to bees, ranging from highly toxic to very low toxicity. The Neonicotinoids represent a class of insecticides that have come under great scrutiny because of their widespread use in food production (as well as for ornamental commodities) and because this class is known to be highly toxic to bees. Neonicotinoids act by affecting an

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The Landsculptor – March 2016 9

ConColor Fir & rhizosphaera needleCast

pollinators and pestiCides in MiChigan landsCapes

The Plant Doctor’sLandscape Tips

By David L. Roberts, Ph.D., Senior Academic Specialist, College of Agriculture and Natural Resources, Michigan State University

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photo 1: A bee “working over” some Spirea flowers in a nursery in western Michigan. Routine sprays of pesticides to control various pests and diseases could adversely affect the bee populations in this fruit, vegetable and field crop production area.

introdUCtion:Higher plants reproduce by producing flowers (recall your Plant Anatomy 101 course) consisting of, among a variety of parts, stamens that produce pollen that fertilize the pistils in flowers. The resulting fruits, nuts and seeds are important for Life on Planet Earth. Humans are dependent upon many of these plants and their products. Plants may be self-pollinated or they may be cross-pollinated by a variety of manners, including wind and physical transmission by insects (bees, flies, beetles butterflies, etc.) and animals (bats, hummingbirds, etc.). Bees represent a significant component of the pollination effort (Photo 1). Bees pick up and disseminate pollen as they feed on a flower’s nectar. Although there are over 4,000 species of bees in North America, honey bees, which are native to Europe, are especially important for pollinating many of our valuable food crops. Some of those food crops are dependent upon bee pollination including orchard fruits, berries, many vegetables and many field crops.

Colony Collapse disorder (CCd): For more than 10 years, bee populations have been in an overall steady decline. During some years, bee populations have declined severely. For example, during a one-year period from 2014-2015, honey bee populations were reported to have declined by 42% in the U.S., causing justifiable alarm to many agricultural producers, scientists and environmentalists alike. Native bee populations have also been reported to have declined. The decline has been blamed on many things including loss of habitat, various bee diseases and pests (example: Varroa mites, which can attack bee colonies), pesticides and even cell phones/towers. Some scientists believe that combinations of certain stressors such as bee diseases/pests and pesticides can stress colonies, making them more susceptible to winter kill.

Continued on page 10

“If bees disappeared from the face of the earth, mankind would only have four years to live.” - Albert Einstein

The cause of bee decline is one of the more controversial topics in science and among agribusiness and the general public at this time, even rivaling the extreme controversy surrounding the 2016 U.S. Presidential Elections.

pollinators, pestiCides and researCh:Because bees are insects, it stands to reason that insecticides could cause harm to these and other beneficial insects. And as with tobacco companies, who denied adverse effects of smoking upon human health, it also seems logical that certain entities will decry harmful effects of pesticides upon bees. Example: “Where’s the proof?!?!” Following are some examples of harmful effects of pesticides upon bee populations; this information gleaned from research:

Pesticides can have direct lethal effects on bees—when flowers are sprayed with insecticides or when insecticides are found in the nectar or pollen of plants. Pesticides may also cause sub-lethal effects; bees with low-dose exposure to insecticides may not find their way back to their hives or they may not be able to feed their larval offspring or they may distribute pesticide-tainted food to their larvae. Affected bees may have a compromised immune system that can then make them more susceptible to attack by various pests and diseases.

Pesticides vary tremendously in their toxicity to bees, ranging from highly toxic to very low toxicity. The Neonicotinoids represent a class of insecticides that have come under great scrutiny because of their widespread use in food production (as well as for ornamental commodities) and because this class is known to be highly toxic to bees. Neonicotinoids act by affecting an

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10 The Voice of Michigan’s Green Industry.10 The Voice of Michigan’s Green Industry.

pollinators and pestiCides in MiChigan landsCapes

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Continued from page 9

ConColor Fir & rhizosphaera needleCastThe Plant Doctor’s Landscape Tips

insect’s nervous system. Inclusive of a variety of insecticides, the Neonicotinoids are represented by the widely used imidacloprid (Bayer Advanced, etc.), and dinotefuran (Safari, etc.) in our

industry. These insecticides are typically soil- or trunk-applied and move upward systemically in the plant; these insecticides are often found in flower nectar and pollen. Interestingly, foliar application of these insecticides tends to remain with the leaves. Some fungicides have also been found to exhibit harmful effects upon bee colonies (see below).

MiniMizing adverse eFFeCts oF pestiCides on pollinatorsFor several decades, responsible people have employed Integrated Pest Management (IPM) practices to not only minimize the use of pesticides in our environment but to also provide for better plant health. IPM incorporates Best Management Practices (BMP) into our arsenal of plant health care techniques. Unfortunately, because of the Global Economy, more and more invasive pests and diseases are introduced into the United States. Some of these introduced, invasive problems include Dutch Elm Disease, Emerald Ash Borer, Oak Wilt, Hemlock Wooly Adelgid, Trellis Rust (Photos 2A & 2B) and Japanese Beetle. Introduced exotics are often very serious if not lethal to a whole genus (many species) or many genera of plants. Because these problems are so serious, they usually require far more pesticide inputs if we want to try to maintain the health of those plants ... especially when compared to native pests and diseases on native plants. The increased pesticide usage for health maintenance of specific plants has the potential to severely and adversely impact our pollinators; it is highly probable that they have already been severely impacted.

Due to the alarming threat that pesticides represent to pollinators (and our environment), the EU and some states such as Oregon have introduced legislation specifically regulating the use of pesticides in regards to pollinators. For example, Oregon has specifically prohibited the use of certain insecticides (example: Imidacloprid) on plants during their time of flowering. Currently, except for some language on pesticide labels (The Neonicotinoids have specific label instructions), no legislation for restriction of pesticides and potential impact on bees exists in Michigan. Nevertheless, as environmental stewards, we can adopt certain practices that might help to minimize pesticide impacts on bees and on our environment.

provide habitat: Environments such as city paved areas and manicured lawns have eroded habitat for bees; yes, weeds in the lawn are actually beneficial to pollinators such as butterflies and bees! The incorporation of plants into urban/suburban landscapes can help to sustain healthy bee colonies. Following are some brief lists of plants that are attractive to pollinators (note: common names sometimes vary from region to region) :

photos 2a & 2B: These pear trees were severely affected by the newly introduced Trellis Rust (2A & Inset, left). Unfor-tunately, the time to protect them from the spores being dis-seminated from the juniper alternate host (2B, right) is during flowering, which may result in toxicity to bees. Because of the relatively narrow window of opportunity to control this disease on pear, the avoidance of treatments during flowering may not result in very effective control. However, fungicide applications before flowering may provide sufficient carryover to protect leaves and shoots during flowering.

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The Landsculptor – March 2016 11

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plants attraCtive to Bee pollinators:

annuals: Ageratum, Zinnia, Aster (Callistephus), Calendula, Cosmos, Dahlia, Sweet Alyssum, Blue Salvia, Sunflower, Snapdragon, and Black-eyed Susan, etc.

perennials: Aromatic Aster (Symphyotrichum), Aster (Aster sp.), basil, Bellflower, Black-eyed Susan, Butterfly Weed & Bush, Clematis, Poppy, Common Yarrow, Crown Vetch, Fennel, Foxglove, Globe Thistle, Hardy Geranium, Hosta, Lavender, Lupine, various Mints, Allium (Onion, Garlic, Leek, etc.), Pachysandra, Peony, Purple Coneflower, Sedum, Thyme, Milkweed, etc.

Wildflowers & “Weeds”: Allium, Aromatic Aster, Coneflower, Cup Plant, Goldenrod (several), Joe-Pye Weed, Mints, Milkweed, Dandelion, Clover, Chickweed, Knapweed, Smartweed, Thistles, etc.

shrubs: Illex sp. (Holly), Chokeberry, Buttonbush, Witch Hazel, Cotoneaster, Ninebark, Elderberry, Mockorange, Potentilla, Privet, Raspberries, Spicebush, Spirea, Sumac, Viburnums, etc.

trees: Ash, Birch, Alternate-Leaved Dogwood (Cornus alternifolia), Black Locust, Callery Pear, Blackgum, Catalpa, Elm, Hickory, Prunus sp (Cherry, Apricot, Peach, Plum, etc.), Crabapple, Redbud, Hawthorn, Japanese Pagoda, Linden (Basswod), Maple, Oak, Serviceberry, Tulip Tree, Willow, etc. (Note: some trees are wind-pollinated and some are bee-pollinated)

Utilize problem-Free plants: Various plants have more serious pest and disease issues than other plants. For example, Colorado Blue Spruce is afflicted with a number of contributing factors leading to “Spruce Decline” (Photo 3). Less susceptible conifers and good substitutes for Blue Spruce include Norway Spruce, Concolor Fir and Serbian Spruce, among others. The exotic Scotts and Austrian pines are susceptible to Diplodia Tip blight, various borers and various needlecast problems. Native Eastern White pine or the alternative conifers mentioned above might make good replacements. In the deciduous area, for example, European Birch is highly susceptible to Bronze Birch Borer while River Birch and Northern White (Paper) Birch are not nearly so susceptible to borers and other issues. Utilize plants that do not require any or as many pesticide inputs.

Minimize pesticide Use: We as a society have grown accustomed to and expect blemish-free landscape plants and food products. The use of certain species or cultivars of plants can help us drastically reduce the use of pesticides (Photo 4). One of the best actions the public can take to improve honey bee survival is to not use pesticides indiscriminately (Photo 4).The days of broad spectrum sprays of insecticides and fungicides for everyone’s landscape (one size fits all) should be behind us.

type of pesticide Use: Pesticides vary immensely upon their activity towards bees. It is best to use pesticides that exhibit low residual and breakdown rapidly in the environment.

photo 3: Spruce Decline is quite prevalent on Colorado Blue Spruce and comprises a complex of various diseas-es and pests. Attempts to maintain healthy blue spruce trees will require extensive pesticide inputs, which may not be very considerate of the health of our bee popula-tions and other non-target beneficial insects.

Continued on page 12

photo 4: In our efforts to strive for perfection in our land-scapes and food production, we often apply pesticides that are not really necessary. Tar Spot, while appearing objec-tionable to some individuals, has very little adverse health impact on our maple trees. In addition, Norway maple is susceptible while native sugar maple is resistant. Hint, hint.

Dursban and Lindane were two insecticides that were widely used and highly effective in this industry until their eventual removal; their primary problem was that these two chemicals could be detected years after their application, including in a variety of locations such as groundwater. Insecticidal Soaps, Horticultural Oils and some Biological Pesticides are believed to have little impact on pollinators. Biological Pesticides that can have less impact on pollinators include: Bacillus thuringiensis

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Continued from page 11

(B.t.), Metarhizium anisopliae, Chromobacterium subtsugae, Azadirachtin (from the Neem Plant), and Spinosad; however, because some can be highly toxic, special precautions need to be taken. There are many products listed as EPA Reduced Risk Products; each product needs to be reviewed and considered on its own merit. Other products are not on the EPA Reduced Risk chart but are relatively safe for bees: for example, Buprofezin as an insect growth regulator is effective on nymph stages for a wide variety of insects with piercing-sucking mouthparts such as scales, plant hoppers and leafhoppers, but has little effect upon bee pollinators.

Fungicides, once believed to be relatively harmless to bees, are now considered in a different light. Fungicides taken back to the hive can interfere with the natural ecology (especially with beneficial fungi) and biological processes (fermentation) within the hive. Fungicides applied before flowering or after petal fall are not expected to have much of an impact on bees (the thought at this time). Some studies, however, have demonstrated that fungicide-contaminated pollen can be toxic to larvae when ingested: examples Captan, Ziram, Iprodione,

Development of Landscape Tips was sponsored by MSU and MGIA.

michigan green industry association

Chlorothalonil, Mancozeb. It has also been demonstrated that when propiconazole is combined with an insecticide, the insecticide can become more toxic to bees. Fungicides in the Stobiluran class (Trade Names examples: Eagle & Heritage) have also been shown to be toxic to bees.

timing of pesticide application: Because bees are pollinators and because they visit plants during their flowering cycle, it is prudent not to apply pesticides during flowering, thus avoiding direct contact of the pesticides with bee activity. Furthermore, it is also advisable to not utilize pesticides when there might be residual carryover into the flowering period. Also because, bees tend to visit flowers during the day time, spraying in the early morning or evening can reduce the risk of direct exposure. Also, when applying pesticides to trees and shrubs that are not flowering, it is wise to be cognizant of overspray or drift to flowering non-target plants.

ConClUsions:Over the past several years, the research on the Colony Collapse Disorder has been ratcheted up, especially in regards to interactions with pesticides. This is a very complex issue. So, why should we care about the utilization of pesticides and bee health? While it may be convenient for those of us in the nursery and landscape industry to consider ourselves far removed from the production of food stuffs, we are nevertheless an integral part of an environment that affects the overall wellbeing of plant and animal life on this planet (Photo 1).

note: For more information on Pollinator and Pesticide interactions, please refer to: “Protecting and Enhancing Pollinators in Managed Urban Landscapes,” by David Smitley, Michigan State University Department of Entomology; Diane Brown and Erwin Elsner, Michigan State University Extension; Paula M. Shrewsbury, University of Maryland Department of Entomology, and Daniel A. Herms, The Ohio State University Department of Entomology. This publication should be available soon from MSU Extension.

The author, MSU and MGIA do not endorse any particular products. If using pesticides, be sure to read and follow label directions.