Protecting Pollinators in Urban Landscapes – Save the Date

Two years ago Elsa Youngsteadt and I from NC State joined forces with Dave Smitley, Heidi Wollaeger, and others from Michigan State University to organize the first national conference related to pollinator conservation in ornamental plant production and urban landscapes. Over 150 people with jobs in research, extension, industry, government, or NGOs spent 3 days in the North Carolina mountains with a lineup of renowned international speakers.

But this conference was not just about listening, it was also about talking and discussing pressing issues such as insecticide safety and habitat conservation. As you can imagine with such a diverse group of people with so many perspectives sometimes we talked louder than others. But that was the fun and enlightening part that made the conference unique.

Folks studying bee conservation had dinner with folks from agrochemical companies. Extension folks trying to find real-world pest management solutions had beers with beekeepers and conservationists. I doubt most of these interactions would have ever happened without this conference.

Well, the conference will return October 9-11, 2017 as the 2nd national conference on Protecting Pollinators in Urban Landscapes. This time in beautiful Traverse City, Michigan. We are still building the program so consider this a save the date. However, you can check out the program from last time to see the diversity of topics and quality of the speakers. If you really want to get out of your (research, conservation, extension, industry, beekeeper) bubble to hear and discuss the state of the art on a range of topics this is the conference for you.

February 15th, 2017|Categories: Lab Happenings, Pollinators, Uncategorized, Urban Ecology||

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 resources for protecting pollinators in urban landscapes

Dr. David Smitley at Michigan State University helps organize the national Protecting Pollinators in Ornamental Landscapes Conference that took place in 2015 in North Carolina and will be held again in Michigan in October 2017.

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Dr. Smitley passed along a new bulletin and article on this topic.  Dr. Smitley also provided a PowerPoint presentation titled “Update on Neonics, Bees and Best Management Practices for Protecting Pollinators and Beneficial Insects On Ornamental Plants” that he presented a couple weeks ago at the Ornamental Workshop in Henderson, NC.

 

November 9th, 2016|Categories: Pollinators, 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: , , , |

Do urban bees eat more junk food than rural bees?

Photo Jun 20, 10 56 06 AMUrban animals eat all kinds of things they would never eat in a ‘natural habitat’. Urban ants eat lots of foods left behind by people on the ground and in garbage bins. Clint Penick from the Dunn Lab recently published a paper showing that some ant species eat more processed human foods in highly urban traffic islands than in parks. Using a similar technique Clint, Cat Crofton, an undergraduate in our lab, and a team of others investigated if city honey bees also eat more soda and sweets than rural bees for lack of flowers. In turns out they don’t. In their new paper Clint and Cat show that honey bees managed by bee keepers consume more cane or corn derived sugar than feral bees because bee keepers provide supplemental sugar to their hives. Feral bees, those living in trees or other places and not managed by people, consume less cane or corn sugar than managed bees. They also seem to find enough flowers and other natural food sources in cities and don’t have to resort to human foods. Good news for bees and picnickers.

May 17th, 2016|Categories: Pollinators, Urban Ecology|Tags: |

Post-doc position available in the Frank Lab

A postdoctoral position is available to work in my lab in the Department of Entomology at North Carolina State University, in collaboration with Rob Dunn in the Department of Applied Ecology, as well as a broader group of scholars studying cities at NCSU.

Funding will be partially or fully to examine how urban heat islands and global climate change affect urban and natural forest health. We are interested in the influence of urban heat islands and, more generally, climate on tree pest physiology, symbionts (of diverse sorts), trophic interactions, and the distribution of tree associated taxa. We also consider how changes in urban tree health and density affect human health.

For more information, check out the full position description, and my lab website to read some of our papers on urban decomposition, urban warming affects on trees, pests, parasitoid phenology, and climate change.

To apply, submit CV, cover letter, and email addresses of three references to Steve Frank (sdfrank@ncsu.edu). Cover letter should include a description of research interests and experience and how they could contribute to the lab and project goals.

Lady beetle approaching an aphid on tulip poplar. Photo: SD Frank

Lady beetle approaching an aphid on tulip poplar. Photo: SD Frank

January 6th, 2016|Categories: Lab Happenings, Urban Ecology|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: , |