Posts Tagged ‘Michigan State University Extension’

Gypsy Moth Attacking Michigan Trees…Again

Ugh, they’re back! Or maybe it’s more accurate to say they never left.

Gypsy moth has been a pest to Michigan trees for decades, ever since it was introduced to the state in 1954. While the invasive pest has never been eliminated, some years seem to be worse than others? This year seems to be particularly bad. Why? One word: drought.

Read the below article by Michigan State University Extension to find out how drought can cause booms in gypsy moth populations.

 

Gypsy moth caterpillars once again attacking trees in Michigan

Large numbers of gypsy moth caterpillars strip trees in Mid-Michigan as drought hampers fungal controls.

Barrier band for gypsy moth larva control. Photo by Pennsylvania Department of Conservation and Natural Resources - Forestry, Bugwood.org.

Barrier band for gypsy moth larva control. Photo by Pennsylvania Department of Conservation and Natural Resources – Forestry, Bugwood.org.

 

They are back! A Clinton County resident contacted the Michigan State University Extension Lawn and Garden Hotline to report heavy caterpillar feeding in maples, pines and apple trees. A few trees had lost much of their foliage. A photo of the caterpillars confirmed it is gypsy moth, Lymantria dispar. For Michigan residents that have dealt with gypsy moths in the past, it is an unwelcome sight but one that is not unexpected.

Twenty to 30 years ago, gypsy moth was a plague across Michigan, defoliating thousands of acres of trees each year. Without many natural controls, it wreaked havoc on oaks, pines, maples, birches, apples and many other species. In 1989, a fungal pathogen was found killing off large populations of gypsy moth caterpillars in Northeastern states. This fungus was identified as Entomophaga maimaiga, a natural biological control of gypsy moth in Japan.

Brought to Michigan in 1991, E. maimaiga quickly became a key factor in suppressing gypsy moth across the state. Naturally occurring in soils, it spreads to young caterpillars as they move from tree to tree. Caterpillars begin to die as the fungus grows inside them. The spores from these dying and dead caterpillars spreads by wind infecting other caterpillars. As the season progresses, large infected gypsy moth caterpillars are found dying on tree trunks. Dead caterpillars remain attached to trunks and branches, hanging straight down. E. maimaiga is so effective that areas of the state often go for years without any noticeable damage from this ferocious defoliator.

So why are gypsy moths back in large numbers and feeding on trees? Drought! The fungus cannot effectively reproduce during times of drought. A year ago much of Michigan was in a serious drought from spring to early summer.  This is the time the fungus is dependent on moisture for its development and of course it is also the time gypsy moth caterpillars begin to feed on trees. Callers to the MSU Extension state hotline in 2016 confirmed that more caterpillars were feeding on trees across southern Michigan. Without consistent moisture in the spring, more gypsy moth caterpillars survived into the moth stage to produce larger numbers of egg masses. It was not unexpected to see growing populations of gypsy moth caterpillars this year.

gypsy moth larva

Gypsy moth caterpillar. Photo by Bill McNee, Wisconsin Dept of Natural Resources, Bugwood.org.

 

Drought is the weak link for the Entomophaga maimaiga fungus and in years when this occurs gypsy moth populations begin to grow and impact landscapes and forests. Spring droughts in 2007 and 2012 led to higher population of gypsy moth the following years. The good news is that in most years we do have adequate rainfall in the spring. Many areas in southern and mid-Michigan had consistent rain this past May, allowing for good development of the fungal pathogen.

Inspect plants now for gypsy moth caterpillars and damage. Trees that lose a large percentage of leaves to gypsy moth feeding can become stressed as energy reserves are used to produce a second set of leaves. Conifers may be permanently damaged if totally defoliated, especially pines. Valuable pines and hardwoods in the landscape can be sprayed with insecticides labeled for caterpillars, or trunks of trees can be banded with a sticky material to trap caterpillars as they crawl up and down trees. This may help on individual trees that are out in the open but may have little effect on trees in the woods where insects can move between adjacent trees.

If valuable trees are infested, you can contact an arborist to spray for the caterpillars. You could also choose to let nature take its course.  In my conversation with the gentleman from Clinton County, we discussed how wet conditions in most of mid to southern Michigan this spring should lead to development of the fungus E. maimaiga. He observed that he was already seeing dead caterpillars hanging straight down, which is a symptom of the effect of the fungus on gypsy moth caterpillars. These dead caterpillars infested with E. maimaiga now become the future source of the fungus in this area protecting trees for years to come.

Michigan is a large state with different weather patterns. While one area is in a drought, another site can be experiencing heavy rains. Awareness of where spring drought occurs can provide an early indicator for possible gypsy moth outbreaks. Nature provides many clues if we pay attention.

New Hemlock Quarantine Possible

It’s a tiny forest pest that is wreaking havoc across the Appalachian Mountain region and one that could cause the same kind of devastation in Michigan if we’re not careful.

It’s called the hemlock woolly adelgid (HWA), a small aphid-like, sap-sucking insect that is responsible for killing thousands of hemlock trees. It’s difficult to find due to its small size, but can begin killing trees as early as 4 years after infestation. The first reported sighting was near Richmond, VA in 1951. By 2005 it had spread to 16 states from Maine to Georgia.

It has been recently identified in west Michigan; first noticed in Muskegon county, but has also been found in nearby Allegan and Ottawa counties. An import quarantine is already in effect for Michigan, meaning that hemlock cannot be brought into Michigan from an infested state. However, since it has been determined that HWA is in several Michigan counties, an in-state quarantine is being considered. This would mean that movement within Michigan would be regulated, especially within the quarantined counties.

With the estimated 170 million hemlock trees in Michigan, including the virgin hemlock forest at Porcupine Mountains State Park, extra caution is a good thing.

 

Michigan is preparing to enact interior quarantine due to invasive hemlock tree pest

A recent outbreak of the pest within the state has prompted new legislation which will restrict the movement of hemlock products within Michigan in an effort to control this invasive pest.

Adelgid infested hemlock branches. Photo credit: USDA Forest Service - Region 8 - Southern, USDA Forest Service, Bugwood.org

Adelgid infested hemlock branches. Photo credit: USDA Forest Service – Region 8 – Southern, USDA Forest Service, Bugwood.org

 

Over the last several years, in reaction to the outbreak of hemlock wooly adelgid in forest stands across the eastern U.S., Michigan banned the shipment of hemlock trees and wood with bark into the state. However, a recent outbreak of the pest within the state has prompted new legislation which will restrict the movement of hemlock products within Michigan in an effort to control this invasive pest.

The exotic hemlock wooly adelgid insect was first identified in the eastern U.S. in early 1950s. It has systematically spread throughout the Appalachian region and is devastating the hemlock tree forest resource by the thousands. In an effort to help protect the estimated 170 million hemlock trees in Michigan, a ban or quarantine on bringing hemlock nursery stock and wood products with attached bark into the state has been in place for some time and was last revised in 2014.

In spite of the efforts to keep this destructive forest pest out of the state, an infestation has been identified in central West Michigan. First noticed in Muskegon County, closer inspection has identified colonies of the tiny sap feeding pest in neighboring Ottawa and in Allegan Counties as well.

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Pale crown appearance with no new growth indicates this tree is under severe attack from Hemlock Woolly Adelgids. Photo credit: James Johnson, Georgia Forestry Commission, Bugwood.org

In an effort to control or slow this tree-killing pest, the Michigan Department of Agriculture & Rural Development (MDARD) solicited public comment on a proposed hemlock woolly adelgid interior quarantine. The original draft stated that “the proposed quarantine, movement of hemlock nursery stock, branches, boughs, uncomposted chips, logs and firewood would be regulated. Specifically, movement out of, or within, the three county area would be prohibited except under compliance agreement issued by MDARD. The proposed regulated area includes Allegan, Muskegon and Ottawa counties.” Other counties may be added as the need arises to further limit the spread of hemlock woolly adelgid.

If the quarantine is enacted, the movement of hemlock trees, boughs, firewood, logs or limbs will be prohibited without a compliance agreement. This restricted movement would include movement within these counties from site to site. (Note: A compliance agreement are actions jointly taken by both producers and the State of Michigan to ensure hemlock nursery stock and wood products are free of the adelgid insect.)

For more information on the hemlock wooly adelgid, Michigan State University Extension has a bulletin available. Extension Bulletin E-3300  details the life cycle and highlights the negative impacts from this invasive killer with some available treatment options should landowners identify adelgid colonies in their trees.

In addition, people interested in becoming actively involved in identifying new infestations of this and other potential forest pests are encouraged to become involved in the MSU Extension Eyes on the Forest program by becoming a sentinel tree volunteer.

The Stink Bugs Are Back

They’re brown, numerous, and annoying. And right now they’re trying to make their way into your homes. Brown marmorated stink bugs.

Every year people are plagued with these pests as they look for warm places to hide for the winter. Unfortunately for us, we’ve made lots of them with our obsession for cozy homes, insulated garages, even storage sheds and barns. All of these provide great protection for these insects during the harsh temperatures of winter.

If you find yourself infested, don’t panic. While irritating, they’re harmless. And there are ways to keep them out of your house.

The article below from Michigan State University Extension gives you a few tips and resources to help.

 

Brown marmorated stink bugs are moving into Michigan homes again

What they are, why stink bugs are entering houses, and what you can do about them.

The brown marmorated stink bug is a shield-shaped, plant-feeding bug native to Asia. It has distinctive banding on its antennae and around its abdomen. Photo: Jeff Wildonger, USDA-ARS-BIIR.

The brown marmorated stink bug is a shield-shaped, plant-feeding bug native to Asia. It has distinctive banding on its antennae and around its abdomen. Photo: Jeff Wildonger, USDA-ARS-BIIR.

It’s that time of year again when brown marmorated stink bugs invade structures humans create looking for a place to hunker down for winter. Since last fall when Michigan residents were asked to report brown marmorated stink bugs in their homes, we now know that brown marmorated stink bugs are well-established as a nuisance pest in homes in the southern Lower Peninsula of Michigan.

What are they doing?

Brown marmorated stink bugs are looking for a protected place to hibernate over winter. They will leave your house again in the spring – if they can find their way back out – to look for plants to feed on and lay their eggs outside.

What are they NOT doing?

They are NOT nesting, laying eggs or feeding on anything or anyone in your house. These are plant-feeding insects with straw-like mouthparts for drinking plant juices – they are harmless to humans and pets.

What do you need to do?

  1. Don’t panic.
  2. Look for gaps around window air conditioners or holes in window screens and block them off – these are easy access points for brown marmorated stink bugs to enter houses.
  3. The easiest, non-toxic way to dispose of them is with a couple inches of soapy water in a bucket – the soap prevents them from escaping the water. Sweep them into the bucket and they will drown in the soapy water, which you can then dump outside. Or you can do the same with a Shop-Vac – add the soapy water to the canister before vacuuming them up with the Shop-Vac.
  4. Report how many you’ve seen at a given location using the Midwest Invasive Species Information Network. If you have trouble entering the information on the Midwest Invasive Species Information Network website, leave a message for Julianna Wilson via email at jkwilson@msu.edu or by phone at 517-432-4766 with your name, address (or nearest crossroads), the date you saw them, and how many you have seen.

The map below shows where we have received reports to the Midwest Invasive Species Information Network of brown marmorated stink bugs in the Lower Peninsula since Sept. 25, 2015.

Map of Michigan counties that have received brown marmorated stink bugs reports

Biology and other tips for managing them in your home: download the free Brown Marmorated Stink Bug (BMSB): Information for Michigan Residents tip sheet from Michigan State University Extension.

Prevent them from entering your home: see “Managing brown marmorated stink bugs in homes.”

Report sightings of brown marmorated stink bugs: see “Report sightings of brown marmorated stink bugs in your home or business.”

Visit MSU’s Brown Marmorated Stink Bug website for 2016 monitoring network reports and additional information.

Be Careful with Water Gardens

You see them all the time, people adding ponds and other water features to their yards or gardens. Done correctly, water gardens are a great way to attract wildlife, create habitat, and add beauty to your property.

Yet there should be caution to this tale. Your choice of plants and animals when planning these features is key. If you’re not careful, your innocent plant purchase might just take over your neighboring lake or river. Please take the proper precautions when choosing plants and animals and when in doubt, choosing native species is always the safest bet.

Learn more about keeping non-native aquatic plants and animals contained in the article below. There’s also some great information in it about the new RIPPLE project, an education program created by Michigan State University Extension and the Michigan Department of Agriculture and Rural Development.

Is your water garden having a RIPPLE effect on Michigan’s waterways?

While water gardens add beauty to backyards, it is important to be aware of the risks associated with aquatic invasive species and to prevent escape.

Build water gardens away from other waterbodies to prevent escape of non-native animals and plants during flooding events. Photo credit: Paige Filice

Build water gardens away from other waterbodies to prevent escape of non-native animals and plants during flooding events. Photo credit: Paige Filice

Wildlife habitat, soothing sounds and scenic beauty are just a few of the benefits of having a backyard pond. Exotic fish such as koi can be attractive additions to your pond, and non-native ornamental plants such as water hyacinth can add beauty. But if let loose, these species can have long-lasting, detrimental effects on Michigan’s lakes and streams. Water garden fish and plants are commonly selected for their hardiness and rapid growth, but these characteristics also contribute to the species’ ability to become destructive and invasive if they escape.

Invasive water garden plants and fish can enter Michigan’s lakes and streams a variety of ways. One of the most common practices is the intentional release of unwanted pets, such as koi and goldfish. This happens most often during the breeding season when fish reproduce rapidly and in the fall when homeowners are preparing their water gardens for winter weather. While releasing unwanted fish and plants into natural waterbodies may seem humane, the consequences to the environment can be devastating. More environmentally friendly alternatives include giving to or trading with another hobbyist, environmental learning center, aquarium or zoo. Some local pet stores will take back unwanted fish and plants. Invasive fish and plants can also escape water gardens during heavy rain events if the pond overflows, so the best location for a backyard pond is well away from other waters.

Aquatic Species of Concern

One common water garden plant of particular concern is water hyacinth. While beautiful with light purple flowers and glossy leaves, it can become very invasive and is on the International Union for Conservation of Nature’s list of 100 of the world’s worst invasive alien species. It can form dense mats on the surface of the water, impeding boat traffic, clogging waterways and interfering with wildlife. Due to its free-floating nature, water hyacinth prevents sunlight from penetrating the water, reducing the growth of native submersed aquatic plants, which many aquatic organisms rely on for shelter and food. Water hyacinth was first introduced to the United States in the late 1800s from South America and has since invaded much of the southern United States. It has been found in southeastern Michigan, including Lake Erie Metropark, where it has persisted for years even though it was commonly believed to be unable to survive Michigan’s winter temperatures. When choosing plants and fish for your backyard pond, consider asking your local retailer for native species. There are many varieties of native aquatic plants that can add great beauty to backyard ponds without as many risks.

Tips to reduce the risk of invasion

Follow the RIPPLE: Reduce Invasive Pet and PLant Escapes program guidelines to prevent escapes. If you have water hyacinth, or any other potentially invasive plant or fish in your pond, and would like to get rid of it, remember to never release it into waterways. It is also important to not compost it, as the seeds can still be viable.

  • Inspect and rinse any new plants to rid them of seeds, plant fragments, snails and fish.
  • Build water gardens well away from other waters.
  • Seal aquatic plants for disposal in a plastic bag in the trash.
  • Give or trade unwanted fish or plants with another hobbyist, environmental learning center, aquarium or zoo.
  • Contact a veterinarian or pet retailer for guidance on humane disposal of animals.

The State of Michigan has laws restricting and prohibiting the sale of some organisms, including plants and fish in the water garden industry. However, it does not include all potentially harmful invasive species such as water hyacinth.

Michigan State University Extension teamed up with the Michigan Department of Agriculture and Rural Development to create the RIPPLE education campaign. It is used to educate Michigan retailers and residents about proper inspection and disposal techniques to keep non-native plants and animals contained and out of Michigan’s lakes and streams. To learn more about invasive species and to report sightings in the wild, visit www.misin.msu.edu.

What is Spruce Decline & What to do about it?

Many Michigan residents have reported that their spruce trees are looking a little…ragged, to say the least. Most are seeing branches dying, starting at the bottom and moving up the tree.

There are several reasons for this, but the most common ones in Michigan are due to fungal infections or insect infestations. The following article by Michigan State University Extension lists several of the ones we typically see.

Do you have a spruce that’s not looking so hot? It might be because of one of these.

 

What is spruce decline and what should you do about it?

Frequently asked questions about spruce decline.

Photo 1. Declining spruce trees. Photo credit: Bert Cregg, MSU

Photo 1. Declining spruce trees. Photo credit: Bert Cregg, MSU

What’s wrong with the blue spruce trees in my neighborhood?

Colorado blue spruce trees have long been among the most popular conifers for landscaping in Michigan and the upper Midwest. Blue spruce trees are widely planted due to their good growth rate, stately form and, of course, their blue foliage. Unfortunately, blue spruce trees are subject to a wide range of insect and disease problems that can impact their growth and aesthetic appeal.

The prevalence of diseases on blue spruce trees has intensified in recent years and trees are declining rapidly in many areas (Photo 1). The key symptom of spruce decline is branch dieback, which progresses over two to four years and renders the plant’s appearance unacceptable for most homeowners (Photo 2). The rapid decline of many spruce trees in Michigan and surrounding states appears to be related to an increase of canker diseases coupled with other disease and insect problems that plague the species.

Decline starts on lower branches
Photo 2. Decline usually starts on lower branches. Photo credit: Dennis Fulbright, MSU

What kind of diseases affect blue spruce trees?

There are three principle types of diseases that affect blue spruce trees: needlecasts, tip blights and canker diseases. All of these diseases are caused by fungal pathogens and each produce specific symptoms that can be useful in diagnosing the problem.

1. Needlecasts. As the name implies, trees with needlecast diseases shed needles. Needlecast fungi often infect needles on the current year’s shoots. As the disease progresses, the needles die, usually the year following the infection. As a result, trees affected by needlecasts often have an outer “shell” of live needles on current shoots and dead needles on older shoots (Photo 3). The two most common needlecasts we find in spruce are caused by the fungal pathogens Rhizosphaera and Stigmina/Mycosphaerella.

2. Tip blights. Tip blights are fungal diseases that typically cause dieback to new, emerging shoots (Photo 4). Tip blights are most common on pines, especially Austrian pines, but can also occur on spruces.

3. Canker diseases. Canker diseases are caused by fungi that infect branches or the main stem of trees. Typical symptoms of cankers are sunken areas along a stem that may ooze resin (Photo 5). Trees may produce ridges of wound tissue around older canker infections as the tree attempts to restrict the fungus’ growth. As cankers develop, they can interfere with the branch’s ability to transport water and nutrients, resulting in the death of individual branches often referred to as “flagging.”

Needlecast disease on spruce New shoot tips Canker disease on branch
Photos 3-5. Left, Needlecasts kill older (inner) needles, but leave newer needles unaffected. Middle, New shoot tips killed by Phomopsis tip blight. Right, Resin oozing from a branch canker caused by Cytospora. Photo credits: Left and middle photo, Dennis Fulbright, MSU; right photo, Michael Kangas, NDSU, Bugwood.org.

What kinds of insects affect blue spruce trees?

Numerous insect pests can impact spruces in Michigan’s landscape, but the two most common are gall adelgids and spruce spider mites. In both cases, the insect pests are tiny and you may need a hand lens to see them. Often times, people are more likely to see the damage as opposed to the insect pests themselves.

1. Gall adelgids. Adelgids are small insects that feed on shoots by sucking plant sap. As they do so, they cause the shoots to deform and produce galls that resemble cones (Photo 6). Damage from gall adelgids is mainly aesthetic.

2. Spruce spider mites. Spruce spider mites cause needle discoloration and eventually kill needles, which can be mistaken for a needlecast disease (Photo 7). Technically, mites are not insects, but are related to spiders. This distinction is important since not all insecticides will control mites.

Cooley spruce adelgid gall Mite needle damage
Photos 6-7. Left, Gall caused by Cooley spruce adelgid. Right, Needle damage caused by mites. Photo credits: Jill O’Donnell, MSU

Why are we seeing increased decline in blue spruce trees?

There are a number of factors contributing to the decline we see in blue spruce trees, including environmental changes, poor site conditions and new pathogens. Colorado blue spruce is native to arid regions in the Rocky Mountains. Michigan’s climate is generally more humid, especially in the summer, which is ideal for fungal pathogens to thrive. In landscapes, Colorado blue spruces have been planted on some sites that are marginal for their success. As a result, they are stressed and more susceptible to fungal pathogens.

Finally, for decades the default diagnosis for most problems with blue spruce has been Rhizosphaera needlecast or Cytospora branch canker. However, a recent survey by Michigan State University researchers suggests two other fungal pathogens, Diplodia and Phomopsis, were much more commonly associated with branch death and tree decline than Cytospora (Photos 8-9). Diplodia and Phomopsis are both considered weak or secondary pathogens, so it is unclear at this point why they appear to cause major disease problems for spruce. Also, in many cases there may be more than one issue that is affecting your tree’s health.

Spruce decline symptoms  Phomopsis canker on branch
Photos 8-9. Left, Decline symptoms moving upward. Right, Wood staining on branch with Phomopsis canker. Photo credits: Left photo, Christine McTavish, MSU; right photo, Dennis Fulbright, MSU.

Can I do anything about these spruce problems?

As with any tree health problem, the first step in dealing with declining spruce trees is to diagnose the problem and identify the cause. For large or important landscape trees, homeowners should contact a professional arborist or tree care company.

For some disease issues, such as needlecasts, fungicides may be effective in preventing or controlling the disease. It is important to note that fungicide treatments for needlecasts only protect new growth. For control to be fully successful, it may take two to three years of yearly fungicide applications. For canker diseases, the effectiveness of fungicides is usually limited. Removing affected branches is usually the best action to improve the tree’s appearance and slow the spread of disease within the tree.

For insect or mite issues, insecticides or miticides can be effective, however selection of the proper product and timing are critical.

Should we continue to plant blue spruce trees?

This is a difficult question. Although spruce decline is widespread and appears to be increasing, it is not a certainty that all trees will be affected. In fact, it is not uncommon to see healthy, thriving spruce trees near or adjacent to trees that are in severe decline. Another complicating factor is that trees may be healthy for a number of years and then begin to decline as they mature and are more difficult and costly to remove.

The likelihood of having success can be improved by planting blue spruce trees on sites with conditions they favor. Key site factors for blue spruce trees are full sunlight, good air movement and excellent soil drainage. Michigan State University Extension recommends homeowners diversify their landscapes to help make their landscapes more resilient to pest and environmental changes, and seek to plant a variety of species wherever possible.

Healthy blue spruce tree
Blue spruce does best on exposed sites with good soil drainage. Photo credit: Bert Cregg, MSU

Additional resources

Print a PDF of this article.

How to Protect Pollinators

With collapsing populations of honeybees all over the country, pollinators are big news right now. There have been several articles and media campaigns lately that all promote what individual citizens can do to help them out. That’s where it all starts right? At home. People may think that what they’re doing is small, too small to make a difference, but when you add up all of those small individual actions throughout a neighborhood, a city, a state…that’s a BIG difference if you ask us.

Even if you don’t have a lot of land you can still help out your local pollinators. This new publication from Michigan State University Extension has everything you will ever need to know about how to make your yard as pollinator friendly as possible.

 

How to protect pollinators in urban landscapes and gardens

A new PDF publication is the complete guide to protecting pollinators while gardening, growing flowers or managing trees, shrubs or turfgrass in urban areas.

How to protect pollinators in urban landscapes and gardens

Many people are concerned about declines in the number of bees and butterflies, especially honey bees and monarchs. To help gardeners and others in urban settings identify how they can protect and increase populations of pollinators, I worked with a team of my fellow entomologists to write a guide full of resources and recommendations. “Protecting and enhancing pollinators in urban landscapes for the US North Central Region” is available online in PDF format for free viewing and downloading.

This online publication includes:

  • The principles of integrated pest management (IPM) for dealing with pest problems while protecting pollinators.
  • Factors that threaten pollinator health.
  • Detailed recommendations for selecting annuals, perennials, shrubs and trees that support pollinators.
  • Unique to this publication, best management practices for managing devastating exotic pests, or troublesome outbreaks of native pests, while minimizing impacts on pollinators. These practices include trunk injections and the use of low-impact pesticides.
  • A detailed phenological table that tells when the most common trees and shrubs bloom so that sprays can be avoided until they are done blooming.
  • A list of 55 references for those that would like to read more on this subject.

Pollinator coverThis resource is a 30-page PDF and will answer nearly every question that gardeners, landscapers and tree care professionals may have about protecting pollinators. The plant material listed and discussed are for the north central region of the United States, but other versions of this bulletin are in progress now to provide lists of plants for other regions of the country.

The title and complete list of authors is: Protecting and enhancing pollinators in urban landscapes for the US North Central Region (Michigan State University Extension bulletin E3314), by David Smitley, Michigan State University Department of Entomology; Diane Brown and Erwin Elsner, Michigan State University Extension; Joy N. Landis, Michigan State University IPM; Paula M. Shrewsbury, University of Maryland Department of Entomology; and Daniel A. Herms, The Ohio State University Department of Entomology.

Dr. Smitley’s work is funded in part by MSU’s AgBioResearch.

“Leaves of Three, Leave it Be.” Easy Right? Well, Not Really.

Leaves of three, leave it be. This common phrase is taught to children all over Michigan. It’s a convenient rhyme meant to steer you away from touching poison ivy and getting a rash. However, this concept is not quite as clear-cut as it seems. There are several other native plants (yes, even though you may hate it, poison ivy is native) that have leaves in configurations similar enough to poison ivy to cause confusion. There is also the fact that it’s not only the leaves you have to avoid, the stems and roots contain the same oily resin. Besides, what do you do in the winter when the leaves fall off the plants? Poison ivy can both creep along the forest floor and climb woody structures like trees. Do you think you’d be able to spot the climbing kind without its leaves?

Well, unless you want to test it in a real life experiment you might want to take a look at this article from Michigan State University Extension on how to identify the plant.

Identifying poison ivy isn’t always easy to do

Don’t spoil your summer fun by coming in contact with poison ivy; learn to identify it so you can avoid it.

Poison ivy is a plant you should learn to identify so that you can avoid it. An oily resin called urushiol, which is found in all parts of the plant, is what causes skin rashes when people come in contact with it. People vary in their sensitivity to poison ivy, but may become more sensitive after repeated exposure to it. One common misconception is that the poison ivy rash itself is contagious. The fluid in the blisters of a poison ivy rash does not contain urushiol and won’t cause the rash to spread. You won’t get poison ivy unless you come in contact with the oil still on someone’s skin or clothing.

Urushiol is easily transferred to clothing, skin, tools or pet’s fur. If contaminated objects aren’t cleaned, contact with the oil on them can cause skin reactions much later. Poison ivy should never be burned as the smoke from burning poison ivy contains the oil and can irritate lungs and nasal passages as well as skin and eyes. See the Michigan State University Extension Bulletin E2946 for more information on how to control poison ivy.

Poison ivy is a very widespread and prolific plant, frequently appearing along the edge of roadways, paths and other disturbed areas. One reason for its wide distribution is due to the fact that its berries are eaten by birds and deer. Over 60 species of birds have been documented to eat poison ivy berries. The seeds are not digested, but pass through the intestinal tract to be deposited throughout the active ranges of animals that eat them. Unlike humans, the animals eating the berries do not become sensitized to the volatile oils and do not experience allergic reactions to the plant.

Poison ivy can be a bit of a chameleon. It looks similar to several common backyard plants including Virginia creeper and boxelder. The leaves of poison ivy may be shiny or dull and the leaf margins may be toothed or wavy, or have no teeth at all. The leaves may be hairy, or have no hairs at all. Its appearance can vary greatly, but in all cases it has compound leaves that consist of three leaflets. The leaflets are 2-5 inches long, green during the growing season and turning scarlet red in fall. The leaves are arranged in an alternate pattern on the stem. The terminal (end) leaflet has a longer stalk than the lateral (side) leaflets.

Poison ivy Poison ivy Poison ivy with flowers
Poison ivy leaves showing variation in appearance. The picture to the right shows poison ivy flowers. Photo credits: Mark Czarnota, University of Georgia, Bugwood.org (left); David Cappaert, Michigan State University, Bugwood.org (middle); and Catherine Herms, The Ohio State University, Bugwood.org (right)

Poison ivy flowers in spring and produces dense clusters of white berries that ripen from late summer through fall and persist through the winter. Poison ivy can take the form of an erect shrub or climbing vine or grow in large colonies along the ground. Poison ivy has aerial rootlets that it uses to attach to the bark of trees. The rootlets have a hairy appearance. Twigs of poison ivy may be covered with fine hairs. The bark of poison ivy is gray.

Poison ivy roots Poison ivy berries
Left, Poison ivy aerial roots. Right, Poison ivy berries in fall. Photo credits: Joseph LaForest, University of Georgia, Bugwood.org (left) and Ohio State Weed Lab Archive, The Ohio State University, Bugwood.org (right)

Virginia creeper, like poison ivy, has brilliant red fall color. Virginia creeper is a vine, closely related to grapes. Its leaves have five leaflets, although very young plants may have some leaflets that appear in threes. The leaves are arranged in an alternate pattern on the stem. It produces small clusters of greenish flowers in spring that mature to blue berries in fall. Although it clings to trees like poison ivy, unlike the distinctly hairy looking aerial roots of poison ivy, Virginia creeper adheres to trees and walls with small, circular pads on the ends of tendrils.

Virginia creeper Virginia creeper blueberries
Left, Virginia creeper has five leaflets and tendrils with circular pads that adhere to trees and walls. Right, Blueberries of Virginia creeper. Photo credits: John Cardina, The Ohio State University, Bugwood.org (left) and James H. Miller, USDA Forest Service, Bugwood.org (right)

Young seedlings of the boxelder tree superficially resemble poison ivy. Boxelder seedlings grow to become large trees with green twigs and alternate compound leaves with three to seven leaflets. Boxelder is in the maple family, and is sometimes known as ash-leafed maple. Boxelder has yellow fall color, lacks the hairy aerial rootlets and does not have berries. The fruits are the typical maple seeds called samaras.

Boxelder leaves
Boxelder leaves. Photo credit: Paul Wray, Iowa State University, Bugwood.org