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.

elsaphoto1-copy

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: , , , , |

Urban environments increase pathogen pressure on honey bees

bee2_elsa1Our lab’s latest paper, co-authored by Elsa Youngsteadt and Holden Appler, was published today in PLOS ONE. We examined pathogen pressure and immune response in managed and feral honey bee workers from hives located in urban* and non-urban environments. We found some very interesting results, and as science usually goes, we now have a lot more questions.

The urban bees we examined in the study, regardless of whether they were feral or managed, had higher levels of the fungal pathogen Nosema ceranae and Black Queen Cell Virus. We also tested the survival of urban bees in the lab and compared it to their more rural neighbors. Survival for bees in the most urban environments was three times lower than for those in the most rural environments.

Given the stress factors that urban settings present to foraging bees (such as pollution and higher temps), it’s easy to imagine that a compromised immune system in the urbanites might be the culprit. Kinda like when you get super stressed and stay up all night cramming for that big exam (or partying) and find yourself with a cold a few days later. But, our data didn’t support this idea; we didn’t observe a stronger immune response in rural bees relative to urban bees. Something else seems to be contributing to the higher pathogen pressures we saw in the urban bees.

We hypothesized that that ‘something else’ could be urban factors working in favor of the pathogens, making them more abundant or easier to transmit between honey bee workers from different hives. Higher frequency of worker visits at scarce urban food sources could increase the likelihood that bees will pick up diseases from their environment (think the public water fountain or the notorious buffet line). The fungal pathogen in question, N. ceranae, has also been shown to benefit from the warmer temps we see in cities.

This study sets the stage for so many more questions. If urban environments indeed enhance pathogen survival and change the way diseases spread through honey bee populations, is this a red flag for native bee species that share floral and other resources in these cramped urban landscapes? Is urbanization harming them too? Could pathogens jump from honey bees to native bees because they are more abundant or doing better in the city environment? April Hamblin and Margarita López-Uribe are looking into some of these questions and trying to tease out the effects urban living has on our neighborhood native bees.

Check out the paper for some more interesting findings not covered here, and stay tuned for more to come in the native bee department.

*the level of “urban-ness” for each hive was determined using the amount of impermeable surface (concrete, pavement, etc.) in the typical radius a worker bee flies from the hive, 1500 m.

November 4th, 2015|Categories: Lab Happenings, Pollinators|Tags: , , |

Gloomy scale crawlers are active and vulnerable

Adult gloomy scale. Photo: SD Frank

Adult gloomy scale. Photo: SD Frank

Gloomy scale, Melanaspis tenebricosa, is an armored scale that feeds on maples and other tree species. It becomes very abundant on red maples on streets and in landscapes and can cause branch dieback and tree death in some cases. It is not unusual to find trees with nearly 100% of their trunk covered in scale. Street trees are particularly prone to gloomy scale. Crawlers of this scale are active now and can be seen on bark and under scale covers. One of the reasons we have found this to be such a pest is that female gloomy scales produce about 3 times as many eggs when they live on relatively warm trees (like in a parking lot) than when they live on cooler trees (like in a shady yard). This amazing work is outlined in a recent paper by Adam Dale.

Control of this scale is complicated because crawlers emerge over 6-8 weeks so it is impossible to treat all the crawlers at once with horticultural oil or other contact insecticide. This is different than in other scales, such as euonymus scale, in which all crawlers are produced within a narrow window of 2 weeks or so. Adam Dale took a video of some gloomy scale crawlers so you can get an idea of how tiny and nondescript they are. This may also give you an idea of why scales are so vulnerable at this stage to the environment, predators, and insecticides like horticultural oil. Once they produce their thick waxy cover they are much less vulnerable to all these factors.

May 21st, 2015|Categories: Feature, Landscape IPM, Urban Ecology|Tags: , , , , |

Cities reduce zombie mothers: How pests escape their parasitoids in cities

Oak lecanium scale eggs within an ovisac. Photo: SD Frank

Oak lecanium scale eggs within an ovisac. Photo: SD Frank

In the Spring of 2011, I was a new Entomology graduate student with no prior experience with insects except the typical ant and bumble bee watching during my childhood. So I spent most nights early in my studies with my face in a microscope looking at scale insects. Scale insects are tree pests, literal bumps on a log that use their straw-like mouths to suck sap from trees. My adviser, Steve Frank, wanted me to figure out if scale insects were developing faster in warmer parts of the city. He wanted me to do this because scales are bad for the trees they live on. Trees we plant to line our streets and keep our city environment livable.

He also wanted me to look into this because insects that develop faster often have an advantage. We had already found that the scale insects were receiving an advantage of some kind in the hottest urban places; oak tree pests called oak lecanium scale insects – sexy name, I know– are around 12 times more abundant where it’s hot in the city of Raleigh than in nearby cooler spots. In other words, if you’re a Raleighite, there are more scale insects where you eat downtown than at your kid’s school (unless your kid goes to school downtown, I guess).

Parasioid larvae in lecanium scale ovisac. Photo: E.K. Meineke

Parasioid larvae in lecanium scale ovisac. Photo: E.K. Meineke

As the season progressed, and the scales started to develop, I noticed they looked pregnant. And not pregnant with their own eggs, a bad kind of pregnant. So I used tiny dissecting needles to see what was going on inside them and found larvae. They were translucent and barely moved. Some were bigger than others. All were tiny and fascinating. Scale insects don’t make larvae, so these larvae had to be from another type of animal. Only rarely do animals actually survive within other animals, so this was a really neat discovery. Though I didn’t know while it was happening, it was one of the sweet moments of being a new student: I got to rediscover something amazing that science has known for a long time. I discovered parasitoids again.

Modified by CombineZPParasitoids are tiny insects, often wasps, that drill holes into other insects or spiders and lay egg(s). The egg(s) hatch and develop within the host, eating it from inside. They often make zombies of their hosts, causing them to behave strangely. But in scale insects, they just hang out and steal resources by feeding on their blood.

I quickly noticed something else: the scales from hotter parts of the city that housed parasitoids kept producing lots of eggs, but the scales from cooler parts of the city produced fewer eggs when they were also housing parasitoids. It seemed like biological control by the parasitoids was failing in the hotter parts of the city.

We document this phenomenon in a new paper and show that, while scale insect development speeds up with warming, parasitoid development doesn’t. We also document that parasitoid control of scale insects fails where it’s hot in the city, likely due to the mismatch in development between the scales and their parasitoids. These developmental mismatches happen due to climate change between species that are associated with one another – predators and prey, pollinators and plants—across the globe, on land and in the sea, and this project documents that these same mismatches can happen in cities due to warming caused by sidewalks.

Cities as a glimpse of the future

This is a guest post by our Research Associate Elsa Youngsteadt about the work and meaning behind her new research published in Global Change Biology.

About a year ago, I found myself sitting ruefully in a patch of chiggery grass by the side of the road near the little town of Bahama, North Carolina, waiting for a tow truck. I had stuck the lab pickup firmly in a ditch. It was tilted at an embarrassing, sickening angle and had one wheel lodged against the mouth of a culvert. Helpful passers-by with chains and four-wheel drives kindly offered to pull me out, but really only made matters worse.

Gloomy scales and the beetle that loves them. Each white or gray bump is a gloomy scale. The twice stabbed lady beetle is one of their predators. Photo: S.D. Frank

Gloomy scales and the beetle that loves them. Each white or gray bump is a gloomy scale. The twice stabbed lady beetle is one of their predators. Photo: S.D. Frank

My memory is already fuzzy about the sequence of events, but somewhere in there— between slipping into the ditch, the failed rescue attempts, and the final arrival of the giant tow truck—I did actually hike into the woods and get what I came for: eight slender red maple branches, clipped from trees growing in NC State’s Hill Forest.

I found my way to this particular spot, ditch and all, by following the trail of a plant biologist who had collected maple branches there more than 40 years ago during the height of the Nixon administration and the Vietnam War. In those days, the forest was cooler. The fevered dog days of summer now average about 1.4 degrees C (about 2.5 degrees F) hotter than they did then—and that should make a difference to the trees and the insects that live on them.

Specifically, it ought to make a difference to gloomy scale insects. These little sap-sucking insects seem to like it hot. My colleague Adam Dale has been studying gloomy scales in the city of Raleigh, and he’s found that street trees in the hottest parts of the city have far more scales—sometimes 200 times more–than those in the cooler parts of the city.

Sad, bedraggled, gloomy scale infested red maple trees. Photo: SD Frank

Sad, bedraggled, gloomy scale infested red maple trees. Photo: SD Frank

The scales drink tree juices, so more scales are bad for trees. A couple of degrees warming can make the difference between a stately shade tree and a sad, bedraggled specimen with dead branches, sparse leaves, and grimy, scale-encrusted bark.

We thought that if warming gives scales such a powerful boost in the city, global warming could do the same thing for scale insects in rural forests. But we still had no direct evidence that what happens in the city represents what happens in rural areas over time.

This seemed like hard evidence to get. Unlike birds and butterflies, the drab, millimeter-long gloomy scale has not invited enthusiastic long-term monitoring. But perhaps we could scavenge scale-insect information from another source—and this is why I became extremely grateful to scores of plant biologists like the one who archived a foot-long maple twig from Hill Forest in 1971.

These historical plant specimens are stored in collections known as herbaria, where they are affixed to stiff pieces of paperboard, labeled, and stacked in mothball-scented cabinets. It turns out that many of these old twigs still have scale insects intact, stuck firmly but inconspicuously to the spots where they once lived.

An herbarium specimen used in the study. Photo: EK Youngsteadt

An herbarium specimen used in the study. Photo: EK Youngsteadt

It made perfect sense that they would be there, but it still felt outlandish when, only 12 branches into my first search in the UNC Herbarium, there was a gloomy scale—the same species that burdens our urban red maples. It was beautifully preserved, looking like it was collected last week instead of 30 years ago. Even on 100-year old branches, the scales looked perfect.

So I counted them. And kept counting them on more than 300 historical specimens from the southeastern US, then matched up their abundance with historical temperatures for the year and location where each specimen was collected.

Gloomy scale covers preserved on an old herbarium specimen. Photo:EK Youngsteadt

Gloomy scale covers preserved on an old herbarium specimen. Photo:EK Youngsteadt

There it was: During relatively cool historical time periods, only 17% of branches had scale insects. But during relatively hot periods, 36% were infested. In other words, scale-infested branches were more than twice as common during hot periods than cool periods—exactly as we would expect if scale insects benefit from warming in rural forests as they do in the city. Furthermore, the most heavily infested twigs were ones that had grown at temperatures similar to those of modern urban Raleigh.

But the historical specimens weren’t the whole story. The past several years have been warmer than even the historically warm time periods, so to test our prediction, we needed to go back to places where those old branches were originally collected, and see if their scale infestations had actually gotten worse.

Thanks to the careful records of those past plant collectors, I was able to track down 20 of the forest sites across North Carolina where red maple branches were collected in the ‘70s, ‘80s, and ‘90s (and only put the truck in a ditch at one of them). At 16 of the 20 sites, gloomy scale populations were denser than they were on the original branches from the same locations. Overall, I found about five times more scales in 2013 than in the earlier decades.

Careful records and herbarium tags from the past helped Elsa relocate the collection sites. Photo: EK Youngsteadt

Careful records and herbarium tags from the past helped Elsa relocate the collection sites. Photo: EK Youngsteadt

This isn’t good news, but it’s also not time to panic about gloomy scales killing our forests. Although the rural scale insects clearly benefited from warming, just as they do in Raleigh, they still never got as abundant as the ones we see in town. The reasons for that difference are an open question (I have some guesses, but that’s a different story). So, although I’d put money on gloomy scales getting more common in rural North Carolina over the next several decades, I wouldn’t yet say how much more common.

But this really isn’t just about gloomy scale. It’s about cities as an advance guard of climate change. If we can look at scales’ response to urban warming and correctly predict their increased abundance due to global warming, can we do it for other organisms, too? Can we do it for functions, like pollination and biological control of pests?

I hope we can start watching urban ecosystems for problem insects and using that information to stand forewarned about future ecological changes in natural areas. The experiments we have made by paving our cities and making them heat up may have much more to tell us about how organisms will handle future warming.

This post is based on a new study:

Youngsteadt, E., Dale, A.G., Terando, A.J., Dunn, R.R. and Frank, S.D. 2014. Do cities simulate climate change? A comparison of herbivore response to urban and global warming. Global Change Biology. doi: 10.1111/gcb.12692. PDF

Urbanization is good for pests and bad for trees

My wife is from a neighborhood outside Baltimore called Lawyer’s Hill. This is where, in the 18th century, lawyers (and I assume doctors and other gentlemen) had country houses and could escape the summer heat. Lawyer’s Hill is only 3 miles from Baltimore but, based on their significant investment in houses and land, it must have provided significant relief. So what was (and still is) the difference between Baltimore City and Lawyers Hill? Trees.

Historic Lawyer's Hill (left) and downtown Baltimore City. Images from Google Maps

Historic Lawyer’s Hill (left) and downtown Baltimore City. Images from Google Maps

Typically shabby red maples with damage by gloomy scales. Notice dead branches and sparse canopy. For more (better) pictures visit Adam's picture gallery featured in the Bulletin of the Ecological Society of America. Photo: SD Frank

Typically shabby red maples with damage by gloomy scales. Notice dead branches and sparse canopy. For more (better) pictures visit Adam’s picture gallery featured in the Bulletin of the Ecological Society of America. Photo: SD Frank

Trees cool the environment by shading houses, roads, and sidewalks that absorb heat. If you have every walked barefoot from the pool (or wherever you spend time barefoot) to your car you know that pavement is hot and that you scurry from one patch of shade to another. All the heat absorbed by pavement that does not radiate into the soles of your feet radiates into the air. Trees also cool the environment by evaporative cooling called transpiration in which they release water vapor through their leaves. Of course there are other reasons cities are hot. Air conditioners, industrial processes, and vehicles all generate heat. An unshaded bus stop is hot but even hotter when the bus is idling next to it.

All this heat can be bad for people. Heat alone poses a risk to human health as does exposure to solar radiation and pollutants that become more concentrated in hot areas. So why don’t cities plant more trees? Many of them do and try to preserve the trees they have. Unfortunately, arthropod pests are more abundant on urban trees and urban tree survival is low.

In two papers released today, Adam Dale, PhD student extraordinaire, has tackled the questions of why herbivores are more abundant on urban trees and what are the consequences for urban tree health. Adam works on gloomy scale, Melanaspis tenebricosa, an armored scale that feeds on almost every red maple within city limits (go look at the closest red maple, then get back to work).

All the gray bumps on this trunk are gloomy scales sucking nutrients from the tree. For more (better) pictures visit Adam's picture gallery featured in the Bulletin of the Ecological Society of America. Photo: SD Frank

All the gray bumps on this trunk are gloomy scales sucking nutrients from the tree. For more (better) pictures visit Adam’s picture gallery featured in the Bulletin of the Ecological Society of America. Photo: SD Frank

Adam came up with a way to count gloomy scale embryos to determine that warm scales produce more babies. For more pictures of scale embryos visit Adam's picture gallery featured in the Bulletin of the Ecological Society of America. Photo: AG Dale

Adam came up with a way to count gloomy scale embryos to determine that warm scales produce more babies. For more pictures of scale embryos visit Adam’s picture gallery featured in the Bulletin of the Ecological Society of America. Photo: AG Dale

In his first “Urban warming trumps natural enemy regulation of herbivorous pests” published in Ecological Applications he shows that urban warming seems to be the primary factor associated with gloomy scale abundance on urban trees. He supports this by identifying an amazing physiological mechanism: scales at warm sites can have 3 times as many babies as scales at sites just 2.5 degrees cooler! Adam’s next question was: So what about the trees? Do scale insects and temperature increase plant stress or reduce tree growth? This is what urban foresters need to know if they are going to make management decisions. Why manage scales if the heat kills trees anyway? Adam’s second paper “The effects of urban warming on herbivore abundance and street tree condition” in PloS One shows that both scale insects and heat are associated with poor tree condition. This means trees with scales and particularly hot trees with scales are more likely to have dead branches, sparse foliage, and generally look worse that cool trees without scales.

Urbanization is increasing and a new paper from Adam Terando and colleagues from NCSU and the USGS Southeast Climate Science Center suggests urbanization will expand more than previously thought. See a piece on The Rise of Charlanta by Rob Dunn. You notice in the image of Lawyer’s Hill that subdivision construction is underway. Each of these house will get a lollipop tree, probably a red maple or worse an ornamental plum, but the canopy will never be restored. To conserve trees and their valuable benefits for human and environmental health we need to understand even more about why pests become more abundant on urban trees and which trees should be planted to establish resilient urban forests. Its clear from Adam’s work that red maples are not a good choice for hot southern cities.

A gallery of photographs of Adam’s research was featured in the Bulletin of the Ecological Society of America.

Bee condos for bee conservation

This guest blog is by April Hamblin an M.Sc. student conducting research on urban bees in our lab.

Osmia atriventris, or a Mason Bee, is one of many bees that will inhabit bee condos. These blue beauties use a combination of mud and leaf pulp to construct their homes. Photograph by Sam Droege, USGS.

Osmia atriventris, or a Mason Bee, is one of many bees that will inhabit bee condos. These blue beauties use a combination of mud and leaf pulp to construct their homes. Photograph by Sam Droege, USGS.

If you haven’t heard the news already, the White House is creating a Pollinator Plan to help create new pollinator habitat.

But habitat for bees does not have to stop (or start) there—YOU can create bee habitat in your very own back yard! Planting more native flowers is a great start, but if you have already landscaped your yard to the hilt or just want to do something simple, bee condos (as my dad calls them) are just the thing for you.

Native bees live in many areas materials. Many species live in the ground such as the small andrenids that come out early each spring. Others make nests in hollow twigs, reeds, or holes in rotten wood. Unfortunately, many of these materials are less abundant in urban yards than in natural areas.

Bee condos use bamboo and other natural reeds to replace these plant materials and create five star living for native bees. But don’t worry, these bees don’t excavate holes to live in. They are also solitary, which means that they live alone instead of socially like honey bees. They have a mild temperament (as long as kids don’t stick their fingers in the nest) and would not become a pest in your home, but a friendly neighbor pollinating your garden. North Carolina has over 500 native bee species! For more beautiful native bee photos visit: https://www.flickr.com/photos/usgsbiml/

Osmia atriventris, or a Mason Bee, is one of many bees that will inhabit bee condos. They come out early in the season, so put up your bee condos in early spring if you want these blue beauties. Mason bees use a combination of mud and leaf pulp to construct their homes. Mason bees separate brood cell in their nests with mud. Each cell holds a pollen ball and one egg to develop into an adult bee one day.

Osmia nest packed with mud and brood. Photograph by Joel Gardner, Wild Bees and Building Homes.

Osmia nest packed with mud and brood. Photograph by Joel Gardner, Wild Bees and Building Homes.

Megachile spp. or leaf cutter bees, will also live in the bee condos. Leafcutter bees fly all summer, so if you get a late start, you will get these fuzzy bees. Leafcutter bees construct their nests with leaf fragments they cut with their powerful mouths, or mandibles.

Close up of reeds in a bee condo in various stages of colonization. Photo: April Hamblin, NCSU

Close up of reeds in a bee condo in various stages of colonization. Photo: April Hamblin, NCSU

You can create a bee condo with inexpensive readily available materials. All you have to do is:

  1. Cut bamboo or natural reeds where they are segmented so one side will be open and the other will be closed (inside hole diameters around 1/8 are most popular).
  2. Zip-tie 30+ pieces of bamboo and place them somewhere sturdy: on a tree, strapped to a metal post, near the shed, etc.
  3. Painting the outside of the bamboo white and/or blue is a great idea to help bees find their way to their new home. This is a great project for all ages and helps native bees find a home for them and their young.
  4. The bee condos are only good for one season though, so you’ll have to make this a family tradition! Remember to be as simple or creative as you want. Bee condos can just be bamboo bundles, a coffee can, or as decorative as bird houses. It’s up to you and your family!

For more detailed instructions on how to create a bee condo please visit Joel Gardner’s

Wild Bees and Building Houses.

April at one of her research sites.

April at one of her research sites.

I have been using bee condos in my research at 20 homes just like yours to determine how aspects of urbanization affect bee communities and nesting. The volunteers tell me seeing the busy bees fly about their business is fun for the whole family and helps us remember the beauty and importance of nature which is too often forgotten.

June 30th, 2014|Categories: Pollinators, Urban Ecology|Tags: , |

Azalea lace bugs hatch earlier at warmer sites

Azaleas planted next to HVAC equipment that blow hot air. The azaleas always get lace bugs first and worst. Photo: SD Frank

Azaleas planted next to HVAC equipment that blow hot air. The azaleas always get lace bugs first and worst. Photo: SD Frank

Azalea lace bugs (Stephanitis pyrioides) are one of the most damaging pest of evergreen azaleas. They overwinter as eggs in azalea leaves and begin hatching around now. I found the very first ones yesterday. I found them near HVAC units that blow hot air behind our administration building. This is my monitoring spot for azalea lace bugs because they always hatch here first. In addition the high temperature always leads to greater abundance and damage too.

The first lace bugs of the year. Photo: SD Frank

The first lace bugs of the year. Photo: SD Frank

This is a great example of how high temperature increases advances pest phenology and increases development rate leading to more generations per year. It is also partly why azaleas planted in full sun have so many more lace bugs than those in the shade (where they belong). In shaded places on campus and in my yard I rarely find lace bugs. You can see our research on how urban warming affects scale insect abundance here.

You can actually scout for lace bugs any time of year since azaleas keep their leaves. You will see damage from the previous year even in winter and fecal spots on the underside of leaves.  Lace bugs overwinter as eggs so if they were there last year they left eggs waiting to hatch this year. Monitor these plants just by flipping leaves to look for tiny new nymphs.

Azalea lace bug damage on leaves from last year with new leaves above. Photo: SD Frank

Azalea lace bug damage on leaves from last year with new leaves above. Photo: SD Frank

Control is best targeted early in the season when nymphs are present for two reasons. First, nymphs are easier to kill than adults and if you kill nymphs before they mature and lay eggs you have a better chance of clearing up the infestation. Second, the longer azalea lace bugs are on your plant the more damage they do. On evergreen azaleas this damage sticks around for a long time so plants may be permanently damaged. So scout your azaleas and get those lace bugs cleared up before damage occurs. Again though the best tactic is not to plant azaleas in full sun (or next to HVAC units) where is is too warm and where natural enemies like green lacewings, spiders, and minute pirate bugs are rare.

April 24th, 2014|Categories: Landscape IPM, Urban Ecology|Tags: , , |