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: , , , |

Frank Lab Brings the Buzz to Bugfest

This is a guest post by Annemarie Nagle

Bugfest1s

Johnny Randall, April Hamblin, and Elsa Youngsteadt at the 2015 Bugfest pollinators booth. Photo: Mary Frasier

Hordes of insects descended upon downtown Raleigh last weekend, and, paradoxically, drew scores of human admirers. Could this mean the winds are changing for our beloved exoskeleton-clad creatures? Thanks to the efforts of several Frank Lab folks and their helpers, the answer is…perhaps.

Bugfest, Raleigh’s annual festival dedicated to all things arthropod was again a huge success in its 19th year, drawing 31,898 visitors. Held by the NC Museum of Natural Sciences, the event featured over 100 booths with arthropod-related displays, activities, food, and specimens.

The Frank Lab crew and helpers from the North Carolina Botanical Garden manned an outdoor booth called “Your Backyard Jungle: Lions, Tigers, and Bees in the Trees,” which focused on native pollinators and parasitoids.

bumblebees

Specimens encased in resin blocks allowed visitors to get a 360 view of native bees and their lifecycles.

Visitors to the pollinator table were treated to a live bumblebee display and an array of pinned and preserved specimens showcasing the diversity of NC’s native bees. The favorite activity for booth volunteers and visitors alike was an ingenious puppet-esque demonstration of how bees pollinate flowers, created by Elsa Youngsteadt. Visitors could use a popsicle stick “bee leg,” dip it in the “pollen” of the male flower, and transfer it to the female flower, which then transformed into a fruit!

Visitors to the booth may have even gotten a few plant lessons sprinkled in with their insect info. Johnny Randall from the North Carolina Botanical Garden contributed his expertise and some beautiful bouquets of different flowers pollinated by bumble bees, hawkmoths, hummingbirds, and other important native pollinators.

The parasitoids had their own table too, complete with microscopes to bring the world of these tiny monsters to life. PhD student Emily Meineke was on hand to share how this important group of insects provides control of unwanted pests—by eating them from the inside out. A poster put together by Kristi Backe showed the who-eats-whom among insects that are found in a typical tree canopy, a surprisingly complex miniature jungle.

Bugfest happens only one mealworm-fried-rice-fueled day a year, but fortunately for us and the plants we depend on, the jungle remains in every back yard for those who know where to look.

September 28th, 2015|Categories: Lab Happenings, Natural Enemies, Pollinators|Tags: |

Banker plant diversity and biocontrol–new paper

A.colemani

Aphidius colemani parasitoid with aphid mummy. Photo: David Cappaert, Michigan State University, Bugwood.org

Our new paper just published in Insects takes a look at whether using a variety of banker plant species enhances biocontrol of green peach aphid by Aphidius colemani in the greenhouse. Check it out here.

September 9th, 2015|Categories: Greenhouse IPM, Natural Enemies|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.

Pachyneuron_small

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

Blastothrix_small

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: , |

IPM Symposium in Western NC – biocontrol, bees, and bugs

The North Carolina Arboretum is holding its annual IPM Symposium this year October 1st from 9:00-4:00. This is a insect_ecologyfantastic symposium that has grown each year. It provides high-level information on IPM from national experts in biological control, pest ID, scouting and monitoring, disease management, pesticide use, and other topics. See the full schedule of speakers and topics then register here. It is a real bargain for such good talks and is one of the few places you can get your fill of biological control info along-side more traditional IPM.

July 15th, 2015|Categories: Greenhouse IPM, Landscape IPM, Natural Enemies, Nursery IPM|Tags: |

New paper: Everything you wanted to know about parasitoids and aphids in greenhouse biocontrol

Aphidius colemani parasitizing an aphid. Photo: AG Dale

Aphidius colemani parasitizing an aphid. Photo: AG Dale

The parasitoid wasp, Aphidius colemani, injects eggs into aphids so their larvae can develop inside. After a week or two an adult wasp emerges dramatically from a hole in the aphid which is now a brown, hardened shell called a mummy. Due to its prowess in hunting down and killing aphids, Aphidius colemani has become the most widely used biological control agents in the world for aphid pests in greenhouse crops. Unfortunately, the level of control can change every time you release A. colemani into a different crop, at a different temperature, or with different aphid species present. In a new paper Frank Lab alums Sara Prado and Sarah Jandricic leave no stone unturned when reviewing the ecological interactions that affect A. colemani efficacy in greenhouses. In a previous paper, Sara Prado showed that the shape and density of the crop plant effects aphid control by A. colemani. Sarah Jandricic has shown that plant species affects A. colemani development, size, and sex ratio. There are dozens of biotic and abiotic factors that could affect aphid biological control by A. colemani.  This paper compiles decades of research on A. colemani and identifies critical research needs.

Prado, S.G.; Jandricic, S.E.; Frank, S.D. (2015) Ecological interactions affecting the efficacy of Aphidius colemani in greenhouse crops. Insects, 6, 538-575. Open access.

This work was funded in part by the Fred C. Gloeckner Foundation and American Floral Endowment.

June 12th, 2015|Categories: Greenhouse IPM, Lab Happenings, Natural Enemies|Tags: , |

Hoverflies – Bee mimics provide pollination and biocontrol services

Hoverfly on Chrysogonum virginianum. Photo: SD Frank

Hoverfly on Chrysogonum virginianum. Photo: SD Frank

You can often see hoverflies zipping in and out of flowers in your garden. They approach a flowering shrub or group of flowering perennials and hover around seemingly deciding which flower to feed from. A nice part about hoverflies is that they frequently land on flowers to rest providing great photo opportunities for even the clumsiest and least patient phone-wielding gardener or child. Hoverflies are often mistaken for bees. This is called Batesian Mimicry after Henry Walter Bates who studied butterflies (among other things) in the Amazon and first described the phenomenon of harmless species mimicking unrelated harmful species as a form of protection from predators. In this case, many hoverflies, which don’t sting, mimic bee species that do making predators think twice before grabbing them.

The superficial similarity continues since hoverflies also pollinate flowers, though not always as efficiently as bees. Hoverflies visit flowers to feed on nectar or nectar and pollen depending on the species. This gives them the energy and nutrients they need to reproduce.

Reproduction is where hoverflies and bees diverge. (Evolutionarily bees and flies diverged a long time ago during). Most hoverflies have free-living predatory larvae. Hoverfly adults lay eggs on plants near aphid colonies. The maggots move within the aphid colony grabbing aphids with their mouths and eating them. These are very easy to find if you want to see them in (slow) action. Look at milkweed, tulip poplar, any plant with a bunch of aphids. Look closely among the aphids and you will often see green or yellow hoverfly maggots.

Hoverfly larva on a tulip poplar leaf. The tree had many aphids. Notice aphid mummies in the background. Photo: SD Frank

Hoverfly larva on a tulip poplar leaf. The tree had many aphids. Notice aphid mummies in the background. Photo: SD Frank

Hoverflies can be valuable for biological control of aphids in crops like lettuce and grains on which aphids are common pests. Hoverflies can fly far into crop fields to home in on aphid colonies and lay eggs. A lot of research has investigated ways to attract and conserve hoverflies and other aphid predators like lady beetles in crop fields by planting flowers.

Even urban yards can have great hoverfly diversity. As you might expect the best way to attract hoverflies is by planting flowers. But remember flowers are not all they need; they also need aphids for the maggots to develop. Maintaining a “pest free” yard reduces the abundance and diversity of all the predators and parasitoids that rely on those herbivores as food. So when you see a few aphids don’t go nuts. Think of them as food for lady beetles (which also won’t lay eggs without aphids present), hoverflies, minute pirate bugs, bigeyed bugs, lacewings, parasitoid wasps, aphid midges, and hundreds of other insects. Expecting to conserve charismatic insects like hoverflies and lady beetles while eliminating aphids and other herbivores is like trying to conserve lions without gazelles, water buffalo, and zebras.

 

June 4th, 2015|Categories: Natural Enemies, Natural History and Scientific Adventures, Pollinators|Tags: |

Millions of scale insect predators hatching…careful they look like mealybugs!

Two larvae on willow oak trunk. Photo: SD Frank

Yesterday on campus willow oak trees were covered in millions of what looked like mealybugs. But they were faster than mealybugs and constantly moving around the tree bark. Mealybugs don’t move much. Matt Bertone at the NCSU PDIC identified them as larvae of lady beetles that specialize on scale insects. This has been a crazy year for lecanium scales. It seems to me like there are more of them on more kinds of trees than ever. As all the lecanium crawlers hatch out these lady beetle larvae are hatching too. These lady beetles are in a couple related genera probably including Hyperaspis spp. You can read more about them in a previous post with great drawings. The important thing is to recognize they are not pests, they are predators so you can calm people (yourself) down who fear for their trees and may what to spray them.

May 15th, 2015|Categories: Natural Enemies|Tags: , |

Aphids and natural enemies on tulip poplar

This time of year tulip poplar leaves are covered in aphids. The great thing about aphids is that they attract a diverse array of predators and parasitoids and even fungi. Therefore, after a few weeks of dowsing your sidewalk in honeydew the aphids almost disappear. Here is a tulip poplar leaf that foreshadows the aphids demise. It has lots of aphids but also lady beetle eggs and a parasitoid mummy. On the same tree I found syrphid fly larvae, green lacewing larvae and eggs, and other predators. Thus, I don’t feel any management is usually necessary for these aphids. In fact I predict that they actually could reduce pests on nearby plants by attracting so many natural enemies.

Tulip poplar leaf with aphids, a cluster of yellow lady beetle eggs, and a brown aphid mummy which houses a parasitoid wasp. Photo: SD Frank

Tulip poplar leaf with aphids, a cluster of yellow lady beetle eggs, and a brown aphid mummy which houses a parasitoid wasp. Photo: SD Frank

May 5th, 2015|Categories: Landscape IPM, Natural Enemies, Nursery IPM|Tags: , |

Do scary parasites mean my yard is healthy?

This is a post by our Research Associate Elsa Youngsteadt about some rare parasites she found.

In a lab full of people quietly staring through microscopes, a startled yelp occasionally breaks the silence. And I admit, it sometimes comes from me. Diving into the magnified world can be a lot like watching a scary movie on a big screen.

Usually the freak-out happens when I’m doing something soothingly monotonous, like counting tiny scale insects on leaves. I get in a groove and forget that I’m seeing everything 30 times bigger than it really is. Then a spider dashes crazily across the field of view: It appears enormous, threatening, bristly, unpredictable, and very, very close. This is when the yelping happens. But of course the beast is actually smaller than a pencil eraser and nowhere near my face, so I feel silly, compose myself, and get back to the scale insects.

But sometimes, the startling thing is something I’ve never seen before, something wild and creepy and totally distracting. This is what happened earlier this year when I settled in to identify some newly collected bees from my yard. These were dead bees, mind you, fresh out of a cyanide jar and expected to sit still and not be startling.

The first few toed the line. There was a shiny, bulbous, blue-green mason bee, and a plain little matte-black sweat bee. A ground-nesting Andrena still had flakes of clay on her jaws. All normal and non-threatening.

Andrena bee with strepsipterans peeking out of its abdomen. Photo: Matt Bertone

Andrena bee with strepsipterans peeking out of its abdomen. Photo: Matt Bertone

Then, the yelp. Spreading across the rear end of the next bee was a mass of very alive, squirmy, maggoty little larvae, looking not-so-very little. I knew in split second what they were, but I admit to quickly popping the bee back in the cyanide jar to finish things off before looking again.

I was witnessing the birth of a brood of strepsipterans—a group of parasites whose wacky life cycle involves a weird, blobby insect eating a live bee from the inside out, while that insect’s own babies eat her from the inside. At the time I caught my bee, the strepsipterans had just finished feeding on their mother and emerged into the world, via a hole in their mama’s head (technically, in her cephalothorax). How else?

Had the bee avoided my net and continued to fly around visiting plants, the larvae would have hopped off on the next flower. (Really, hopped: Despite the initial maggoty impression, these are leggy, nimble little insect tykes.) Each one would have waited at the flower-airport to board a fresh bee, which would carry it back to an underground nest tunnel. There, the strepsipteran would find the bee’s egg or larva and burrow in—disappearing inside within a few hours.

The strepsipteran then loses its legs and eyes and grows along with its young bee host. Eventually it fills the bee’s abdomen, stunting its organs and altering its development. Female Andrena bees, for example, develop the angular cheeks and hairy abdomens typical of males. (They also become very hard to identify.) One researcher even reported finding a bee with a single, giant eye arching over its head like a headband–perhaps a strepsipteran-induced developmental glitch.

Strepsipterans emerging from Andrena bee abdomen. Photo: Andrew Ernst

Strepsipterans emerging from Andrena bee abdomen. Photo: Matt Bertone

As adults, male strepsipterans have wings and return the outside world to fly around for a few hours before they die. Females, however, remain ensconced in their bees, with only their heads visible from the outside. (That’s the smooth, yellowish tissue you can see sticking out of the bee’s abdomen in the photos.)

The rest of her body is “a great sack full of eggs,” wrote entomologist W. Dwight Pierce in 1909. The thousands of eggs simply float around inside the mother’s body, absorbing nutrients from her blood. Eventually, they hatch and trek to the outside world via the “brood canal” that exits their mother’s head. Which is where they were when they made me shriek.

This whole stranger-than-fiction setup is more than just a titillating insect freak-show. As parasites, strepsipterans may have an important role in maintaining insect diversity. Parasites tend to regulate their hosts’ populations in ways that prevent any one species from becoming outrageously common—leaving room for more species overall. That process keeps ecosystems diverse and food webs stable.

Stepsipteran larvae emerging. Photo: Andrew Ernst

Stepsipteran larvae emerging. Photo: Andrew Ernst

I would bet that strepsipterans are among the parasites that help maintain diversity, although their role has never been measured. There are about 600 species of strepsipterans in the world, and they can also be found in planthoppers, cockroaches, grasshoppers and wasps. In the bee and wasp species that have been checked, 10 to 30% of individuals carry strepsipterans and are unlikely to reproduce.

That means strepsipterans are common enough to regulate the abundance of their hosts. In a tantalizing example, the European paper wasp (Polistes dominula) left its strepsipterans behind when it moved across the Atlantic to North America—and none of the North American species will parasitize it. So researchers have suggested this wasp’s fast reproduction and dominance over native North American wasps may be due, in part, to the loss of its parasites.

Of course I have no way of knowing where my one bee with her alarming brood of squirmy strepsipterans fits into the big picture. But I’d like to think she’s a good sign. I’d like to think that if I kept looking I would find that my messy yard is teeming with a diversity of slightly creepy parasites, keeping their hosts in line and yielding an endless supply of microscopic scary movies.

November 25th, 2014|Categories: Feature, Natural Enemies, Natural History and Scientific Adventures, Pollinators|Tags: |