Would you give a few minutes a year to reveal the future of forests?

What would be the easiest citizen science project ever? Watching paint dry? Falling off a log? Maybe. But what would you, or anyone else, learn from that?

We are starting a citizen science project almost as easy but much more important. Its called A Tree’s Life and all you need to do is monitor red maple growth in your yard. We even give you the supplies. It’s really just one supply called a dendrometer, and it does most of the work.

We want to measure trees because they have a very important job to do. Trees take carbon dioxide (a greenhouse gas) from the air and release oxygen. Even more important, though, is that they use the carbon to build more tree tissue. That’s how they grow, and as they grow, they store carbon that would otherwise remain in the atmosphere.

Dendrometers are flexible plastic rulers that are installed on the tree’s trunk and expand as the tree grows. Photos: Michael Just

Trees provide many other services like filtering air and water, providing shade to reduce energy costs, and generally make life better. Unfortunately, warming from urbanization and from climate change can reduce tree growth due to water stress, pests, and other factors. In other cases warming might make trees grow more and become healthier due to a longer growing season.

The problem we want to address is that no one knows how trees in different habitats (urban, suburban, rural) and different latitudes will respond. So how can one predict the rate of carbon accumulation in the atmosphere, and thus climate change, if we don’t know how the primary terrestrial carbon sinks – trees – will respond? We can’t. Can we predict where urban trees and forests will thrive or decline? Not very well.

Our goal is to monitor the growth, and thus carbon sequestration, of hundreds or thousands of trees to help figure this out. If you have a red maple and a few minutes each year, please help us. You will contribute to our (all of humanity’s) understanding of how climate change and urbanization will affect forest health and carbon sequestration by trees.

Find out more about the study and sign up to participate.

March 7th, 2017|Categories: Feature, Urban Ecology|Tags: , , |

As spiders leave the kitchen, pests keep cooking

A spider in the family Anyphaenidae has made its home on a twig infested with scale insects.  Photo: Emily Meineke, Harvard University

I think by now most people accept that we can’t hope to preserve all extant creatures over the next 50 or 100 years. Global changes in temperature and habitat will help some species and hurt others, as Elsa Youngsteadt showed in her recent paper. Since we can’t save every creature, what is really important to protect? Increasingly, people try to understand and protect species and ecological interactions that generate ecosystem services for people, rather than diversity per se.

Former undergraduate researcher Anna Holmquist examines branches in the field. Photo: Emily Meineke, Harvard University

Urban warming makes street tree temperatures similar to what is expected under climate change, so we have studied them to predict the effects of warming – urban and global – on pest abundance and tree health. Street trees also host a surprising amount of arthropod diversity if you just look hard enough. In a new paper, our former graduate and undergraduate students, Emily Meineke and Anna Holmquist, with help from Gina Wimp at GWU, studied the effects of warming on spider communities in street tree canopies.

The team tested two predictions. Spiders like to eat and often become more abundant in places where prey is more abundant. So we predicted that, since heat increases herbivore abundance, spider abundance would follow. However, because some spiders probably benefit from warming while others do not, we predicted the composition (member species) of the spider community would be different in hot and cool trees.

The fitness of this spider probably increases with warming since it is hot and sweaty from exercise and yoga. Other spiders (not pictured, you can only work kids so hard) die in, or leave, hot places. Thus, yoga spiders will be more common on hot trees and the community composition will change. Artwork by: I.F.

Ghost spiders, like this one, are nondescript but perform important ecosystem functions. Photo: Matt Bertone, NCSU.

Spiders were by far the most abundant natural enemy group. However, as herbivore abundance increased with warming, spider abundance stayed the same. This is bad news for trees because it means that herbivores can increase unchecked. Instead, urban warming altered spider community structure due in part to a whole family of spiders, Anyphaenids — aptly named ghost spiders – virtually disappearing from the hottest trees in one year of the study. This is bad news for conserving urban biodiversity and also because ghost spiders feed on particular pests like lace bugs.

In this experiment, warming reduced biodiversity but also likely reduces biological control by predators, an important ecosystem service. Something happens in these trees to make a common ecological interaction – predators congregating to prey – stop happening. The consequence is that pests go nuts and trees suffer.

Read the full paper here:
Meineke, E.K., Holmquist, A.J., Wimp, G.M., Frank, S.D. (2017) Changes in spider community composition are associated with urban temperature, not herbivore abundance. Journal of Urban Ecology, 3 (1): juw010. doi: 10.1093/jue/juw010.

January 26th, 2017|Categories: Feature, Natural Enemies, Urban Ecology|Tags: , , , |

Who wins and loses with warming? Where you live matters.

Climate change is generally considered bad for people, earth’s biomes, and, of course, polar bears. But as the climate warms will all critters suffer? Will they all be affected the same way? No. In addition to the losers who slowly fizzle out under the oppressive heat, there will be winners who benefit from warming.

An animal’s response to climate change depends largely on two things: the amount of warming in a habitat and the physiological limits of the animal. It has been shown pretty convincingly that animals closer to the equator are more sensitive to warming than animals farther north. I know what you are thinking, “but tropical animals are hot all the time, they should be used to it.” I thought the same thing, but how it works is that since they are hot all the time, they live close to their thermal limits. So for animals in hot places, a little more heat pushes them over the edge.

Therefore the biological effects of climate change are expected to vary geographically, particularly for ectothermic animals such as insects. Elsa Youngsteadt and other folks in the lab took a road trip to test the hypothesis that insects at high latitudes, where it is cold, should generally benefit from warming whereas insects at low latitudes should have mixed responses: some should benefit, but others should be pushed over their thermal limits.

In a brilliant new paper Elsa reports her findings from this trip. The team sampled insects from street trees in the hottest and coolest parts of four cities–Raleigh, Baltimore, Queens, and Boston–taking advantage of the urban heat island effect as a natural warming experiment.

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Four cities at different latitudes were chosen to study warming effects on insect communities. Background map from the National Biomass and Carbon Dataset.

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One of the authors, Andrew Ernst, takes measurements at a typical study tree. Photo: E.K. Youngsteadt


In the lowest latitude city, Raleigh, some taxa became more abundant with warming while others declined. This suggests that, although some species benefited from warming, just as many species suffered. In the coldest and highest latitude city, Boston, most insect groups were unaffected or became more abundant, suggesting that warming was good for most species living in a frigid northern metropolis. Just as predicted! This doesn’t happen very often.

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Yellow sticky cards were used to sample insect communities in urban trees. Photo: E.K. Youngsteadt.

It seems good that not all taxa tank in Raleigh–but the fact that some benefit and others decline could be ecologically disruptive, too: Maybe a parasitoid and its host respond differently, or a predator and its prey. This sort of mismatch could lead to extinction of higher trophic levels if the prey does poorly, or herbivore outbreaks if the predator fails.

I’ll warn you upfront, this paper is dense and there are probably a lot of new concepts packed in that most people will need time to unpack. However, capturing the response of a whole community to a couple degrees of warming is novel and worth the read. Think about the responses of your favorite organisms. Not just in cities but across the globe.

Read the paper here.

December 16th, 2016|Categories: Urban Ecology|Tags: , , , |

New paper: Urban warming reduces aboveground carbon storage

This is a guest post from our former student (now postdoc at Harvard) Emily Meineke.

Through years of studying urban trees and the insects that eat them, we, the Frank lab, have discovered that warming in cities leads to more pests. We also know how: where it’s warmer, insects survive and reproduce better, and the effects of their natural enemies are diminished. In most conversations we have about this work, explaining these discoveries leads to the question: but what does this mean for the trees?

Street trees perform essential services like removing pollutants from air. Photo: EK Meineke

Street trees perform essential services like removing pollutants from air. Photo: EK Meineke

I tackled this question with the help of Elsa Youngsteadt by studying how warming and pests affect tree drought stress and functions like photosynthesis and stomatal conductance. Of course, as in my previous work, I studied the charmless but interesting oak lecanium scale on willow oaks which are among the largest and most common street trees in Southeastern cities.

Oak lecanium scales on willow oak. Photo: EK Meineke

Oak lecanium scales on willow oak. Photo: EK Meineke

Over three years we took hundreds of tedious measurements (thanks Elsa!) to figure out how fast our trees were growing and thus how much carbon they were removing from the air and storing in their tissue. This is called carbon sequestration and is a critical way trees reduce carbon pollution and global warming.

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Elsa measuring photosynthesis. Photo: EK Meineke

In a new paper, we show that the urban heat island effect significantly reduces street tree growth. This is because trees in warmer urban areas photosynthesize less. When these effects were scaled up to all the willow oak street trees in Raleigh, warming reduced citywide carbon sequestration by 12%. However, insect pests like scales and spider mites had minor effects on tree growth compared to warming, at least in the short term.

Oak spider mites damage leaf cells and reduce photosynthesis. Photo: EK Meineke

Oak spider mites damage leaf cells and reduce photosynthesis. Photo: EK Meineke and A Ernst

These results lead to several recommendations for urban forest management. First, because urban and global warming are becoming more intense, urban trees will store even less carbon in the future. However, managers may be able to reduce these effects by planting trees that are more tolerant of hot urban conditions. This highlights the need for research to identify what trees are appropriate to plant in hot urban environments. In general, this research makes us excited about science that will help landscape designers tailor green infrastructure for resilience to climate change and intensifying urbanization.

Our results also highlight the utility of cities as large-scale natural climate experiments, in which sessile organisms, such as trees and many insect herbivores, are confined to different thermal environments in close proximity. The range of urban warming they experience parallels the extent of global warming expected regionally, outside the city, over the next several decades. Therefore, cities can serve as experiments that allow scientists to address questions that are otherwise difficult or impossible to approach, such as the effects of warming on mature trees.

Meineke, E.K., Youngsteadt, E.K., Dunn, R.R., Frank, S.D. (2016) Urban warming reduces aboveground carbon storage. Proceedings of the Royal Society – B 283: 20161574 DOI: 10.1098/rspb.2016.1574

October 7th, 2016|Categories: Urban Ecology|Tags: , , , , |

Emerald ash borer cropping up in new NC counties

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Silhouette of an ash tree infested with EAB showing classic thinning in the crown. Photo: David Cappaert, Bugwood.org

Emerald ash borer is continuing to spread through NC. So far this summer, it’s already been found in four new NC counties (Davidson, Forsyth, Swain, and Yancey). At this rate, the NC Forest Service is anticipating a lot more findings and is asking folks to keep their eyes peeled for tell-tale signs of beetle activity.

Check out this month’s Forest Health Note for more info on EAB in NC.

July 21st, 2016|Categories: Urban Ecology|Tags: , , |

Impervious surface cover is bad for trees. How much is too much?

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Gloomy scales on red maple. Photo: AG Dale

We have studied the effects of urban warming and other factors on tree pests and tree health for several years. The gist of it is impervious surfaces increase plant stress by warming the atmosphere and reducing water availability. Adam Dale and Elsa Youngsteadt studied the effects of impervious surface cover on red maples to determine how much is too much? In a new paper they answer this question to create an impervious surface threshold that planners and planters can use to determine if sites are suitable for red maples. Their analyses of impervious surface cover and red maple condition in Raleigh, NC indicate that red maple condition is most likely to be excellent or good if impervious surface cover is less that 32% within a 25m radius. At 33% to 66% impervious surface cover, trees were most likely to be in fair condition. Above 66% impervious surface cover, trees were mostly in poor condition.

 

Good to know but how do you measure impervious surface cover? Not many landscapers are going to pull up satelite images on their phones and bust out ArcGIS to measure the amount of impervious surface around a tree. Instead we came up with the Pace to Plant technique. With this technique anyone can acurrately measure impervious surface cover at 25 m radius just by pacing transects and counting the steps that fall on impervious surfaces.

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With an impervious surface threshold in hand hopefully landscape architects and other planners will not specify red maples on plans when impervious surface cover is high. Tree care professionals on the ground will also be able to assess if a planting site is suitable for red maples. Two small (even medium) steps for urban tree IPM.

May 17th, 2016|Categories: Landscape IPM, Urban Ecology|Tags: , , , |

Maple Shoot Borers Damaging Maples in Nurseries

This is a guest post by our PhD student Larry Long.

MSB Flagging (Long)

Flagging of apical shoot and frass expelled from larvae developing inside the stem and beneath the lateral leaves. Photo Credit: Larry Long, NCSU

Maple shoot borers (Proteoteras aesculana) are common pests of red maples in nurseries. This caterpillar causes flagging and dieback of the apical shoots of maples (Acer spp.). It is too late this season to manage this pest or damage with insecticides but recognizing the damage could inform your management next spring. Maple shoot borer adults are small nondescript moths that lay eggs on maple stems near expanding buds in early spring. After hatching the caterpillar burrows into the growing shoot where it feeds on the vascular cambium. As the larvae develops it expels frass and silk from the hole through which it entered the stem. Young stems and leaves above the point where the larvae entered eventually die.

Mature larvae exit the shoot then pupating on the ground. There is no evidence of summer season egg laying so it is thought that upon emergence from their pupae the new moths seek overwintering sites.

Monitoring for damage by this pest is not very useful because by the time damage occurs management is impractical. However, if a high proportion of plants are infested this year it could warrant preventive insecticide applications next spring. To confirm that damage is from maple shoot borers and not another pest like potato leafhoppers, cut open flagging stems to see if they are hollow and if larvae are present. The larvae are a tan to cream-colored with a dark head capsule.

Dissected maple stem showing larvae living inside. Photo Credit: Matt Bertone, NCSU

Dissected maple stem showing larvae living inside. Photo Credit: Matt Bertone, NCSU

Preventive management entails applying pyrethroid insecticide from just before bud break until shoots have flushed their first two pairs of lateral leaves. Since this is in early spring you may be making these applications anyway for ambrosia beetle management so there is no need to spray extra just for maple shoot borer. Preventive applications are important because once symptoms appear it is too late for treatment. Damaged shoots should be pruned and a new leader trained to correct tree form.

Dieback or ‘flagging’ caused by maple shoot borer. Photo Credit: Larry Long, NCSU

Dieback or ‘flagging’ caused by maple shoot borer. Photo Credit: Larry Long, NCSU

See our guides for IPM of of trees and shrubs in nurseries on our extension resources page.

May 13th, 2016|Categories: Nursery IPM|Tags: , , |

Rare sight, common occurrence: Parasitoid wasp emerges from a scale insect

This is a guest post by PhD student Emily Meineke

Coccophagus lycimnia freshly emerged from a gloomy scale.  Photo: Emily Meineke

Coccophagus lycimnia freshly emerged from a gloomy scale. Photo: Emily Meineke

If I’ve learned anything during my graduate career, it’s how to count scale insects. On a rainy June day, I sat at a microscope with forceps trying to discern bark from insects that mimic bark. My targets were armored scale insects, which are essentially tiny bags of plant sap. The adult females have vestigial or no legs, and move around only in the beginning of their lives. The rest of the time, they lie under a cover built from their excrement and wax and eat plants. If they outbreak on a plant in your yard, you might think it looks sad and kind of grey. But you might never know who did it.

Usually these excursions under the microscope are Zen, which is to say not very exciting. But on this day, I saw something rare, an event that happens every day everywhere but is almost never seen by people. I saw a tiny head peeking through a tiny hole in one of the scale insects’ covers. And when I poked the cover, it started chewing its way around the hole.  Here’s a video I took of it in action.

This was a parasitoid wasp, specifically Coccophagus lycimnia, which is a jack-of-all-trades, yet master plant protector. I found it attacking gloomy scale, a maple pest, but Coccophagus lycimnia attacks all kinds of scale insects, including armored scales, soft scales, and mealybugs, in forests, cities, and orchards, which is to say, pretty much everywhere on a slew of plant species (see Universal Chalcidoidea Database). It is an especially effective parasitoid of soft scales, in that it attacks immatures and prevents oviposition, while many other parasitoid species reduce egg production in soft scales but do not prevent it.

Parasitoids protecting street trees are diverse. We’ve documented upwards of 10 species that attack one scale insect species. While people run into certain parasitoids often—you’ve probably seen tomato hornworms covered in braconid cocoons—those that attack street tree pests are difficult to observe because they are smaller and live up in trees. They look like gnats to the naked eye, but under a microscope their metallic armor is striking and makes me wonder what else in the world I’m missing because I haven’t looked hard enough.

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Pachyneuron sp., another parasitoid that protects trees. Photo: Andrew Ernst

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Blastothrix sp., another parasitoid that protects trees. Photo: Andrew Ernst


Parasitoids are natural, free pest control along with other natural enemies like lady beetles. Insecticide applications can kill them, including Coccophagus sp. (Suma et al. 2009). Horticultural oils are effective against many scale insect species and can serve as a non-toxic alternative for natural enemies.

References

Universal Chalcidoidea Database: http://www.nhm.ac.uk/research-curation/research/projects/chalcidoids/database/

Suma P, Zappala L, Mazzeo G, Siscaro G (2009) Lethal and sub-lethal effects of insecticides on natural enemies of citrus scale pests. Biocontrol, 54, 651-661.

For more information

Rakimov A, Hoffmann AA, Malipatil MB (2015) Natural enemies of soft scale insects (Hemiptera: Coccoidea: Coccidae) in Australian vineyards. Australian Journal of Grape and Wine Research, 21, 302-310.

Tena A, Soto A, Garcia-Mari F (2008) Parasitoid complex of black scale Saissetia oleae on citrus and olives: parasitoid species composition and seasonal trend. Biocontrol, 53, 473-487.

August 12th, 2015|Categories: Natural Enemies, Urban Ecology|Tags: , |

Emerald ash borers found attacking white fringe tree – fluke or phenomenon?

Emerald ash borer adult. David Cappaert, Michigan State University

Emerald ash borer adult. David Cappaert, Michigan State University

As reported by Entomology Today, Emerald ash borer, Agrilus planipennis, has recently been found to attack white fringetree, Chionanthus virginicus, in Ohio. This is the first non-ash host recorded for emerald ash borers since they were discovered in Michigan in 2002. In a recent paper published in Environmental Entomology, researchers Don Cipollini and Chad Rigsby at Wright State University inspected white fringetrees and Chinese fringetrees, Chionanthus retusus, at Spring Grove Cemetery and Arboretum in Ohio and The Morton Arboretum outside of Chicago. They found 32% of white fringetrees at one site and 43% at the other were infested with emerald ash borers. In some cases it was clear the trees had been infested for multiple years.

No Chinese fringetrees were infested with emerald ash borers. This make sense because emerald ash borers are indigenous to Northeast China so trees there have likely evolved resistance mechanisms. Chinese ash trees are also more resistant to emerald ash borers than North American ash species. The researchers confirmed this resistance by trying to rear emerald ash borer larvae on both fringetree species and a closely related tree, Devilwood (Osmanthus americanus). No larvae developed on the Chinese fringe trees. On white fringetrees larvae survived the 40 day experiment developing to 4th instar but were smaller than larvae reared on highly susceptible green ash. Few larvae survived on devilwood and those that did were small 2nd instars rather than 4th so this does not appear to be a good host.

White fringetree flowers. William M. Ciesla, Forest Health Management International, Bugwood.org

White fringetree flowers. William M. Ciesla, Forest Health Management International, Bugwood.org

White fringetree and Chinese fringetree are frequently planted along streets and in residential and commercial landscapes. Its popularity is increasing as an alternative to other white-flowering trees such as Callery pear. Along Raleigh streets there are 580 white fringetrees 60% of which have been planted in the last 5 years.

Host switching by emerald ash borer from ash to fringe tree is obviously bad news.  We need more research to determine what is driving this phenomenon.

Does emerald ash borer only switch to fringetree after all the ash trees are gone? Do beetle populations have to be at a certain level so competition drives them to try new hosts? Was there a genetic anomaly in these populations that allowed these beetles to succeed in fringetrees when other may have failed? These are all things we need to know before treating or removing white fringetrees from our yards and streets.

So far emerald ash borer is patchily distributed in North Carolina and we do not have as many ash trees on streets or in natural areas as the Midwest and northeast. If this host-switch is a function high emerald ash borer density then maybe we will never get there. Much more work needs to be done.

July 28th, 2015|Categories: Landscape IPM, Uncategorized|Tags: , |

Caterpillars eating your river birch? You should take a closer look.

This is a guest post by PhD student Adam Dale.

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Dusky birch sawfly larvae feeding on river birch. Photo: A.G. Dale

This weekend as I was walking my dog down the greenway I noticed several heavily defoliated river birch branches overhanging the trail. Upon closer examination I saw several groups of a dozen or so yellow-green bodies with black spots and black heads chomping away at the leaves. When I reached up to grab a branch and take an even closer look, almost in unison they all swung their rear ends away from the leaf margin forming little S-shapes. This is the dusky birch sawfly, Croesus latitarsus.

Sawflies are relatively common leaf-eating pests of many landscape trees and shrubs. Different species usually specialize on one plant species or group of plants. Although easily confused with Lepidopteran (butterflies and moths) caterpillars, sawflies are actually Hymenopteran (bees and wasps) pests. The larvae are the damaging stage, which pupate in the soil after getting their fill of leaves, and turn into a winged, wasp-like adult. Don’t worry, though. It can’t sting you.

Typically, sawflies are shinier than caterpillars. However, the best way to distinguish between sawfly larvae and caterpillars is by counting the number of prolegs (the suction cup-like nubs along the rear underside of the body). Caterpillars always have five pairs of prolegs or less, while sawflies have six or more. As you can see in the photo, dusky birch sawflies have six.

As its name suggests, the dusky birch sawfly feeds primarily on birch trees, most commonly river birch in North Carolina landscapes. It is found throughout the United States and has two generations per year in NC. Right now they are in the larval stage of their second generation. Since these pests feed in groups, they tend to defoliate entire portions of a canopy and can clean the foliage off of an entire small tree. Despite this, they seldom reach high enough numbers to cause any lasting damage to a tree and rarely require intervention.

Defoliation by dusky birch sawfly larvae.

Defoliation by dusky birch sawfly larvae. Photo: A.G. Dale

If you’re concerned about them damaging your trees and you can reach them, just pluck them off and toss them into some soapy water or prune the whole branch. If you can’t reach them, you probably didn’t see them until they were pretty far along. Therefore, they’ll be gone soon and killing them now won’t prevent much damage. If you catch them early, good coverage with horticultural oil is effective and populations of larger individuals can be controlled with reduced-risk insecticides like spinosad. Products like Bacillus thuringiensis (Bt) will not work on them since they’re not caterpillars.

One interesting note is that I only saw clusters of these leaf-eaters on branches overhanging the paved greenway trail. When I ventured off trail into the forest they were nowhere to be found. It appears that they prefer the trees along the edges of the forest over the trail, perhaps because it’s sunnier, warmer, easier to find, less dangerous, or tastier. Edge effects like this aren’t unusual and can be caused by various factors. Remember that when scouting for pests like this and look at the prolegs if you’re not sure what it is.

July 27th, 2015|Categories: Landscape IPM|Tags: , |