Spring and eastern tent caterpillars are a month early

Eastern tent caterpillars in the second week of March 2017. Photo: SDF

Last week I went looking for small new nests in hopes I could find eastern tent caterpillars just as they hatched. What I found were large nests with large caterpillars. March is pretty early for eastern tent caterpillars in Raleigh. This is a result of the warmer than ‘normal’ spring we have had. Based on State Climate Office Growing degree day calculator Raleigh (RDU airport) has accumulated 346 GDD (base 50F) so far in 2017. This is not so different than the 316 GDD accumulated by March 27 in 2016. However, it is almost threes times as many as in 2015 (150 GDD), 2014 (92 GDD), and 2013 (108 GDD).


In 2013 and 2014 we did not reach similar GDD until the third week in April putting us almost a month ahead this year. Interestingly, this matches when Google indicates that most people are looking for information about eastern tent caterpillars. According to Google Trends, ‘eastern tent caterpillar’ as a topic in the Raleigh area has peaked in mid-April (e.g. April 6-12, 2014; April 19-May 9, 2015) each year since 2012. This year we already see a peak March 19-25.

Eastern tent caterpillar

Such large changes in insect phenology is important for many reasons. In some cases phenology of mutualists like pollinators may become unsynchronized. In other cases, predators and prey or parasitoid and host phenology may become unsynchronized leading to loss of biological control. Not many people probably care about eastern tent worm prosperity or that of other pests like cankerworms. However, if these critters hatch before their host plants develop leaves they starve. This means migrating birds and other animals people do care about, and that rely on spring caterpillars for food, also suffer.

Of course monitoring and predicting pest activity is an important part of IPM for caterpillars and other pests. The more pest development varies from year to year, or even from warm to cool spots in a city, the harder IPM becomes. Your state probably has a State Climate Office with a growing degree day calculator. As phenology gets more variable, using these tools rather than relying on previous years to implement IPM tactics will be essential.

March 29th, 2017|Categories: Feature, Landscape IPM|Tags: |

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: , , , |

Cicada Killer Wasps Are on the Wing

This is a guest post by our Research Associate Elsa Youngsteadt

A male cicada killer perches atop a retaining wall, keeping watch over his territory. (Photo: E. Youngsteadt)

A male cicada killer perches atop a retaining wall, keeping watch over his territory. (Photo: E. Youngsteadt)

North Carolina’s steamy July days bring out some of our most spectacular solitary wasps. These sleek and streamlined hunters are quite docile toward humans, but are to be feared by other insects and spiders. The largest of these wasps in North Carolina is the cicada killer (Sphecius speciosus). Females can be up to an inch and a half long and weigh about a gram—as much as a shelled almond.

Cicada killers are solitary, meaning that each female typically builds her own nest and hunts prey to feed her own offspring. (In this habit, they differ from yellowjackets, hornets, and paper wasps, which live in social colonies.) Nevertheless, cicada killers do tend to be found in groups, since they all agree on what makes a good nesting area: sparsely vegetated, southeast-facing slopes or unmortared retaining walls, with plentiful cicadas in nearby deciduous trees.

NC State’s campus hosts a few such cicada-killer neighborhoods, and we started to see the wasps out and about last week. But they haven’t quite gotten around to killing cicadas yet.

Although individual cicada killers have unique markings, they differ from other, similar species in size, body shape, and overall color pattern. (Photo: E. Youngsteadt)

Although individual cicada killers have unique markings, they differ from other, similar species in size, body shape, and overall color pattern. (Photo: E. Youngsteadt)

Males emerge a week or two before females, and spend their time feeding at flowers or sap and establishing territories, where they perch on vegetation or stones to keep watch. They make sorties to chase off other males, pursue females, and investigate intruders—including you, your pet, or your camera lens. Once you know that males cannot sting, these hovering advances (described by one pair of biologists as “businesslike”) can seem quite charming.

This male thoroughly investigated me and my camera before settling down for a photo shoot. (Photo: E. Youngsteadt)

This male thoroughly investigated me and my camera before settling down for a photo shoot. (Photo: E. Youngsteadt)

When the females finally emerge, they mate—only once, but for a long time (30 to 50 minutes). When they settle on a good spot for a nest, the earth-moving begins, and herein lies the occasional conflict between cicada killers and humans. One female wasp can excavate nearly a half-gallon of soil for a single burrow, which can be up to 40 inches long! And she makes about four burrows in her lifetime. She piles the tailings in a neat but largeish U-shaped mound at the entrance of each burrow, and this pileup can damage turf and other plants. But keep reading.

Cicada killers also benefit trees by hunting large insect herbivores—namely, dog-day cicadas in the genus Tibicen. These are the camo-colored, thumb-sized insects that spend their brief adult lives in July and August shrieking and buzzing in the treetops or sawing into branches to lay their eggs.

In her lifetime, one female cicada killer can gather 100 or more cicadas (a hundred!)–each of which weighs about twice as much as she does. She paralyzes the cicada with her stinger and hauls it laboriously back to her nest. She brings one cicada for each of her male offspring, and two or three for each female. (The wasp knows in advance the sex of the next egg she will lay, and stocks the nest accordingly). Then she lays an egg at the base of the cicada’s middle leg and seals up the nest chamber that contains it, never to meet her offspring.

The eggs hatch in a day or two and the long-necked larvae develop quickly, each one polishing off a whole cicada in less than four days. Upon completing its meal, the larva spins a silken cocoon and enters diapause, remaining in a suspended state until the following May or June, when it pupates. That brings us back to the present season, when adult wasps emerge and dig their way out of their nursery tunnels in July—males first.

Entrance to a cicada killer burrow between stones in a retaining wall. (Photo: E. Youngsteadt)

Entrance to a cicada killer burrow between stones in a retaining wall. (Photo: E. Youngsteadt)

If you have cicada killers on your property and find that you really can’t endure them, despite their docile manner and benefits for trees, there are few proven options for control. One study in West Virginia eliminated cicada killer activity on a golf course by spraying the appropriate insecticide directly into active burrows, or immediately around their entrances. (Broader area sprays were not particularly effective.)

However, because the developing larvae may survive this treatment, and because good nesting habitat remains appealing to new females year after year, wasp removal will likely be an annual battle. In most situations, the benefits controlling cicada killers with insecticides are unlikely outweigh the financial and environmental costs.

Other wasp biologists have recommended fertilizing and liming the soil in the affected area to promote thicker vegetation that will eventually deter the wasps; one has informally demonstrated a laborious but effective control method that involves plugging burrows and using a badminton racket to swat the wasps. (Again, this would be an annual undertaking.)

I hope that you don’t have to go to all that trouble, and that you can enjoy watching these insects, instead. And stay tuned for updates on our campus wasps. Once we find females dragging cicadas to their nests, there will be another photo shoot!

Sources and further reading:

Dambach, Charles A., and Eugene E. Good. 1943. Life history and habits of the cicada killer in Ohio. The Ohio Journal of Science, 43: 32 – 41.

Evans, Howard E., and Kevin M. O’Neill. 2009. The Sand Wasps: Natural History and Behavior. Harvard University Press. pp 37 – 43.

Hastings, Jon M., et al. 2010. Size-specific provisioning by cicada killers, Sphecius speciosus, (Hymenoptera: Crabronidae) in North Florida. Florida Entomologist 93: 412 – 421.

Holliday, C. W., and J. R. Coelho. Improved key to new world species of Sphecius (Hymenoptera: Crabronidae). Annals of the Entomological Society of America 99: 793 – 798.

Weaver, Joseph E. 1995. Life history, habits, and control of the cicada killer wasp in West Virginia. West Virginia University Agricultural and Forestry Experiment Station, Circular 161.

There is also a wealth of information, videos, and ideas for controlling cicada killers at the websites of biologists Chuck Holliday and Joel Coelho.

July 20th, 2015|Categories: Feature, Natural History and Scientific Adventures, Urban Ecology|Tags: |

Bagworms hatching…scout conifers or other plants with weird ‘pine cones’

If you have conifers or other plants that seem to have grown weird, dangling pinecones, look again because you have bagworms. Bagworms have been hatching for the last week or so. You can find the tiny caterpillars with tiny upright bags anywhere there are bags left from last year.

First instar bagworms with tiny upright bags. Photo: AG Dale

First instar bagworms with tiny upright bags. Photo: AG Dale

The Bagworm, Thyridopteryx ephemeraeformis, is a very common pest of conifers and other ornamental plants throughout the eastern United States. These pests overwinter as eggs within the mother’s bag. Larvae emerge from the bag during the May and June (depending on location and temperature). The larvae crawl or drift via silk strands to nearby foliage where they begin to feed. Bagworms are relatively sedentary during their lifetime, most often remaining on the same tree until they pupate. Adult females are wingless and never leave the tree. Male bagworms develop into a small brown moth.

Large bagworm feeding on maple. Photo: SD Frank

Bagworms feed on plant foliage and heavy infestations can defoliate trees and shrubs. Young caterpillars produce a silk bag on their posterior end that gradually collects plant debris. This creates a bag covered in pine needles or leaves that protects them from predators and looks (sort of) like a pinecone. Since they don’t move much as larvae and the females don’t fly, they can build up dense populations. Since they are so camouflaged and protected from insecticides, management of these insects can be difficult and time consuming. One of the most effective, yet time consuming methods of treatment are hand-picking or cutting the female pupae bags off of the branches. When this is impractical or impossible, there are chemical control options available that should be applied when caterpillars are young (now) because they are more vulnerable. As with many other pest insects, bagworms are susceptible to predation from parasitoids and birds which can also assist in their control.

PhD student Adam Dale contributed to this post.

May 21st, 2015|Categories: Feature, Landscape IPM|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: , , , , |

Cottony Fluff on Trees and Shrubs – Felt Scales

Oak eriococcid scales on a willow oak twig. Photo: AG Dale

Eriococcidae is a family of scale insects commonly called ‘felt scales’. This is a different family than the common soft scales (Coccidae) that includes species like wax scale, lecanium scale, terrapin scale, and cottony maple leaf scale. Felt scales look a lot like mealybugs. The one that is most abundant now is the oak eriococcid scale. If you look at many urban willow oaks this time of year you will see small cottony fluffs, like Q-tips,  on the bark, twigs, and branches. In some cases they become extremely abundant.

This is not a well-studied group of scales. Not much is known about their biology or management.

This is the underside of an oak eriococcid scale. Notice the orange eggs building up toward the back of her body. Photo: AG Dale

This is the underside of an oak eriococcid scale. Notice the orange eggs building up toward the back of her body. Photo: AG Dale

The oak eriococcids have one generation per year. The cottony sack you see now is the ovisac (egg sack). If you dig around in the cottony material you will see tiny yellowish eggs. Pretty soon crawlers will emerge from the cottony mass to find a spot to settle and feed. They also produce honeydew so these are some of the scales responsible for the tiny drops on your windshield if you park under willow oaks or other infested species. Heavily infested trees like some on campus make the sidewalk black with sooty mold.

Other felt scales of importance are the azalea bark scale, European elm scale, and the new crape myrtle bark scale. Control of felt scales has also not been studied well. However, like their aphid and mealybug relatives, imidacloprid and other neonicotinoids should provide some control. If you watch for the crawlers (soon!) you could make a dent with horticultural oil. The oak eriococcid sscales are one of the earliest scales to produce eggs in Raleigh. They are harbingers of all the other scale crawlers to come.

April 2nd, 2015|Categories: Feature, Landscape IPM, Urban Ecology|Tags: , |

Emerald Ash Borer in Wayne Co. North Carolina – Quarantine Implemented

David Cappaert, Michigan State University

Emerald ash borer has been present in North Carolina since June 2013. Granville, Person, Vance and Warren counties have been under EAB quarantine since then. Now EAB has been found at the Cherry Hill Research Facility in Goldsboro, NC. You can read the NCDA&CS press release here. Emerald ash borer is a very destructive exotic pest that has killed millions of ash trees in the Midwest, mid-Atlantic, and other regions.

EAB exit hole. Photo: Pennsylvania Department of Conservation and Natural Resources - Forestry Archive

EAB exit hole. Photo: Pennsylvania Department of Conservation and Natural Resources – Forestry Archive

If you notice ash trees with canopy dieback, sucker growth, or general decline inspect the trees for D-shaped exit holes. You can remove bark to look for larvae and serpentine galleries. Comprehensive biology and management information is provided by a consortium of universities at http://www.emeraldashborer.info.

Home and landowners are encouraged to report any symptomatic activity in ash trees to the NCDA&CS Plant Industry Division hotline at 1-800-206-9333 or by email at newpest@ncagr.gov. The pest can affect any of the four types of ash trees grown in the state.

EAB Larvae. Photo: David Cappaert, Michigan State University

EAB Larvae. Photo: David Cappaert, Michigan State University

March 31st, 2015|Categories: Feature, Landscape IPM, Urban Ecology|Tags: , |

Clumsy native bees benefit you and me

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

What comes to mind when you think of bees and pollination? Most people immediately think of honey bees and bumble bees, but forget the native bees that inhabit the many natural and urban landscapes around us. In fact, there are more than 500 species of native bees in North Carolina alone.

A great deal of research has shown that these wild bees actually pollinate better than the managed, exotic honey bee. Why is this, you ask? It turns out that the native bees are less efficient than honey bees at holding on to all of the pollen grains they collect, which allows for more efficient pollination as it falls from their bodies. This is great for the plants themselves and anyone that likes to eat plants and their products. Native bees have also been shown to continue foraging in not-so-ideal-bee weather, such as cloudy days, when honey bees like to stay inside their hives.

Apis mellifera

Honey bee (Apis mellifera). Photo: Laura Daly

Melissodes bimaculata

Native bee (Melissodes bimaculata). Photo: Laura Daly

 

On the left is a honey bee (Apis mellifera) and on the right, a native bee (Melissodes bimaculata). The bright yellow dots you see on the bees are pollen. What you may notice is that the honey bee keeps most of its pollen neatly packaged on its hind leg in a specialized pollen carrying basket called the corbicula. In contrast, the wild Melissodes bimiculata uses nearly its entire body to collect pollen. In bee species other than the honey bee, any body part modified to carry pollen is called the scopa.

Here is a good way to think about the difference between these two pollen-carrying systems, and the resulting differences in pollination efficiency. Imagine you were trying to carry four boxes of donuts to your co-workers in the morning. Carrying the boxes neatly stacked in your arms would be the honey bee method. If you were using the native bee method, you’d hold them with your arms and feet, try to balance some on your head and back, maybe even a shoulder–and guess what? You’d drop lots of donuts. It is the same for the native bees that carry pollen in many different places–lots of it falls off as they visit new plants, making them excellent (if slightly clumsy) pollinators.

March 31st, 2015|Categories: Feature, Natural History and Scientific Adventures, Pollinators, Urban Ecology|Tags: |

Ambrosia beetle traps are filling up

The granulate ambrosia beetle, Xylosandrus crassiusculus, is the primary ambrosia beetle pest of nurseries in the Southeast. Today we found a similar ambrosia beetle species – the first of the season – in our traps at the NCSU Lake Wheeler Research Station in Raleigh.

Xyleborinus saxeseni. Photo: Pest and Diseases Image Library, Bugwood.org

Xyleborinus saxeseni. Photo: Pest and Diseases Image Library, Bugwood.org

The beetle we found was Xyleborinus saxeseni which is commonly called the fruit tree pinhole borer. This species is also a pest of nursery trees and usually becomes active before granulate ambrosia beetles. However, with the warm weather we’ve had the full suite of ambrosia beetles will be out soon. It is time to protect trees if you haven’t started already. Spray susceptible trees with permethrin every three weeks or so. Ambrosia beetles damage many deciduous tree species and prefer dogwood, redbud, styrax, magnolia, cherry, Japanese maple, and others. You can find more in a free nursery production guide (available as an iBook) and in an article I wrote for American Nurseryman. Although it is time to spray (at least in Raleigh) it is not time for irrigation. We have found that over-watering makes trees more susceptible to ambrosia beetle attacks.

March 12th, 2015|Categories: Feature, Landscape IPM, Nursery IPM|Tags: , , |