Feral honey bees offer tools for managed honey bee health

Honey bee. Photo:SDF

People have domesticated many different plant and animal species to utilize for food, fiber, or other resources. To domesticate a plant or animal people deliberately breed individuals that have valuable or desirable traits – big ears in corn, longer shelf life in vegetables, less fat (unfortunately) in pigs, large, dry flavorless breasts in chickens. The value and desirability of these traits are in the eye of the beholder.

Organisms cannot excel at everything. Breeding to enhance one trait inevitably diminishes another trait. This is called a trade-off and occurs in most domesticated plants and animals. Crops bred for greater yield often have lower resistance to pests and diseases. Animals often have the same problems; bred for rapid growth domestic pigs, chickens, cows often have lower immune function or resistance to disease.

Honey bees have been on the world stage for several years since beekeepers have experienced higher than normal colony losses. Despite all the attention and even affection honey bees have received many people are surprised to learn they are domesticated, exotic, animals just like other livestock. And, as with other domesticated animals, bees have been bred for traits such as honey production, overwinter survival, and easy handling.

A wild honey bee colony lives in the hole in this tree. Photo: SDF

As animals are domesticated the genetic diversity of the population often declines. Genetic diversity can help individuals and populations survive environmental stress and disease. In a new paper, Margarita Lopez-Uribe (former postdoc from the Tarpy, Dunn, and Frank labs now faculty at Penn State) and co-authors compared genetic diversity of feral and managed honey bee colonies. In a previous paper, Elsa Youngsteadt, Holden Appler and others reported that feral honey bees had greater immunocompetence than managed honey bees.

In the new paper, we looked to genetic diversity as a possible mechanism. Feral colonies had less genetic diversity than managed ones. However, transcription of immune related antimicrobial peptides increased as genetic diversity increased in feral colonies but not managed colonies. This suggests that the genetic diversity that does exist in feral bees, perhaps due to natural selection for optimal genotypes and immune variants, improves their immune function. Genetic diversity in managed colonies, from artificial selection for desirable traits, does not improve immune function.

Thus, there may be a trade-off between having bees with traits desirable to beekeepers and bees that can fend off the constant onslaught of diseases to which honey bees are subjected. Scientists and beekeepers are working from every angle to improve honey bee health and sustainability. They should look to feral bees, that survive in the wild without the pesticides and medicines used in managed colonies, for novel genetic variation that could improve disease resistance.

López-Uribe, M.M., Appler, R.H., Youngsteadt, E., Dunn, R.R., Frank, S.D., Tarpy, D.R. (2017) Higher immunocompetence is associated with higher genetic diversity in feral honey bee colonies (Apis mellifera). Conservation Genetics. doi:10.1007/s10592-017-0942-x

This study was funded by the CALS Dean’s Enrichment Grant from North Carolina State University (to DRR, SDF, and RRD) and a National Science Foundation (NSF) Postdoctoral Fellowship (1523817 to MMLU).

February 23rd, 2017|Categories: Uncategorized||

Warm days likely bring ambrosia beetle attacks

Frass tooth-pick from adult ambrosia beetles boring into trees. Photo: SD Frank

With several days of warm weather be on the look out for ambrosia beetles in your nursery. You are trapping right?

Keep checking those traps. I already have reports of a few beetles trapped in the eastern part of the state. Do not over-water your trees. Media moisture over 50% makes trees more attractive to beetle attacks. Many species, like dogwood, are never attacked when media moisture is below 50%.

Read up on our past ambrosia beetle posts, industry publications, new media moisture thresholds, and a review in the Journal of IPM.

February 21st, 2017|Categories: Uncategorized||

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||

New Bee BMP Summary from HRI

Photo: SD Frank

The Horticultural Research Institute just released a pdf summarizing some BMPs for protecting pollinators from insecticides in greenhouse and nursery production and in landscapes. The crux of it is read the label and follow some basic IPM practices like using alternative management tactics. However, there is also good advice like do not drench ‘bee attractive’ plants with clothianidin, dinotefuran, imidacloprid, or thiamethoxam. And, avoid spraying plants with these products within 3 weeks of shipping. Find other information in a previous post highlighting resources from Michigan State and on the ecoipm Native Pollinator Site.

January 27th, 2017|Categories: Uncategorized||

Azalea caterpillars feeding now

Young azalea caterpillars feeding on a partially defoliated twig. Notice frass collecting below. Photo: SD Frank

Young azalea caterpillars feeding on a partially defoliated twig. Notice frass collecting below. Photo: SD Frank

Just a short post here to announce the arrival of azalea caterpillars for this year. Azalea caterpillars, Datana major, are among our most attractive caterpillar species. The feed primarily on Rhododendron spp. but I have also found them on blueberries. There is one generation of this pest each year. Adults lay eggs on the underside of azalea leaves where the small caterpillars feed gregariously. As they grow the caterpillars change from yellow with black stripes to black with yellow patches. Usually, these (and other caterpillars0 are noticed by the damage rather than by noticing the actual critters or eggs. Thus, by the time they are noticed azalea caterpillars may have consumed a lot of foliage. Scout for these caterpillars by scanning shrubs for bare twigs then look closer to investigate. You may also see collections of frass on leaves that indicate caterpillars feeding above. If you find a group of them just prune the branch out. In larger infestations or nurseries there are several insecticides active on caterpillars but any product works best on small stages. Find other posts on azalea and related caterpillars here.

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White azalea caterpillar eggs. Photo: SD Frank

September 3rd, 2015|Categories: Uncategorized||

A big caterpillar family or family of big caterpillars? Notodontids are big, beautiful, and flexible

There are many caterpillars in the family Notodontidae that feed on urban trees and shrubs. Several closely related Notodontids are among the most common late season defoliators of urban trees. These include the greenstriped mapleworm, (Dryocampa rubicunda) which feeds primarily on red maples and orangestripped oakworms (Anisota senatoria) that feed primarily on oaks. We have written about these critters on the blog, in Insect Notes, and in a free book so you can get your fill (maybe you already have).

Greenstripped mapleworm larva. Photo: AG Dale

Greenstripped mapleworm larva. Photo: AG Dale

Members of the genus Datana are among the most beautiful caterpillars ever to defoliate your plants. Around here these include azalea caterpillars (Datana major), and yellownecked caterpillars (Datana ministra). These two species are about the same size and have a defensive behavior someone should name a yoga pose after (Datan-asana?). When approached caterpillars arch their front and back ends to form a ‘C’ shape. This must be scary to some predator or they wouldn’t do it (neither would sawfly larvae). Perhaps it looks like a snake about to strike or maybe it is just unusual and visually arresting enough to make predators like birds think twice.

Late instar azalea caterpillar. Photo: SD Frank

Late instar azalea caterpillar. Photo: SD Frank

In host range azalea and yellownecked caterpillars are quite different. Azalea caterpillars feed almost exclusively on azaleas and occasionally on blueberry plants. Yellownecked caterpillars feed on a long list of species including oaks, maples, fruit trees, elm, hickory, beech, linden, and many others. Feeding habits and life histories of both species are similar to orangestripped oakworms. They hatch from clusters of eggs laid on the bottom of leaves in late summer. Young larvae feed gregariously defoliating one branch at a time. Larvae leave the plant to pupate underground until the next summer.

I found large yellownecked caterpillars on a willow oak last weekend. Azalea caterpillars come out later than yellownecked caterpillars or orangestripped oakworms. I have not seen any yet and usually find them around the end of August. Last year I found eggs hatching the first week in September.

 

Late instar yellownecked caterpillar on willow oak. Photo: SD Frank

Late instar yellownecked caterpillar on willow oak. Photo: SD Frank

Start monitoring for azalea caterpillar egg masses now by turning over leaves to look for egg masses. Also scan azalea shrubs and hedges for branch tips with skeletonized or missing leaves. This is the first sign of young caterpillar infestations and can be pruned to prevent more defoliation.

 

August 11th, 2015|Categories: Uncategorized||

Emerald ash borer – fringetree update: Phenomenon not Fluke

Emerald ash borer adult. David Cappaert, Michigan State University

Emerald ash borer adult. David Cappaert, Michigan State University

Last week I wrote a post about recent research by Don Cipollini and Chad Rigsby at Wright State University documenting that emerald ash borers, once thought only to infest ash (Fraxinus sp.) will also infest white fringetrees. Since then I spoke to Dr. Cipollini who filled me in on some more details about his work with emerald ash borers. He also directed me to a press release and video that provide more information about this discovery and its implications.

To start with, Dr. Cipollini has found emerald ash borer-infested white fringe trees at many sites in Ohio and around Chicago, beyond the formal study sites -Spring Grove Cemetery and Arboretum in Ohio and The Morton Arboretum outside of Chicago- reported in the paper. From these additional observations it seems emerald ash borers infest white fringetrees whenever they overlap.

So why has no one noticed this before? Partly because no one was looking but also because the states first infested with emerald ash borer, like Michigan, are outside the range of white fringetree. Also, Dr. Cipollini has noticed that attacks on white fringetree are not always successful. He finds galleries below the bark that did not yield adults and the diagnostic D-shaped exit hole. Also, white fringetrees heal over exit holes very quickly. These factors mean that live infested white fringetrees are difficult to detect. In recently infested states where white fringetree is common, like North Carolina, this phenomenon may be more noticable.

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

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

As to whether a adaptation or a genetic anomaly allowed some emerald ash borers to infest white fringetrees -the fluke or phenomenon question I raised- Dr. Cipollini sees it as a phenomenon based on the many observation they have made and genetic work showing that borers from fringetrees are not different than ones that infest ash trees.

Experiments from Dr. Cipolinni’s lab show that white fringetrees smell a lot like ash trees to insects; they have a similar volatile profile. Thus, when emerald ash borers become established in a new area they attack both tree species if they are available. In this way North Carolina could make a good experiment to document when fringetrees get attacked relative to their proximity to ash trees and emerald ash borer arrival. Emerald ash borer spread is just underway in NC and we have a lot of white fringetrees.

August 4th, 2015|Categories: Uncategorized||

Orangestriped oakworms – A great case study of landscape IPM

In the last two weeks or so orangestripped oakworms (Anisota senatoria) hatched and have been feeding on urban oak trees. Last week I found caterpillars that had just hatched and some that were 3 or 4 cm long on trees at the same site. Orange striped oakworms have one generation per year. Adults emerge in mid summer and lay clusters of yellow eggs on the bottom of oak leaves. In Raleigh eggs usually hatch around August first. Young caterpillars are yellow and feed gregariously. They start skeletonizing leaves, leaving most fine veins intact. As they grow, larvae become black with increasingly noticeable orange stripes. Large larvae consume entire leaves, leaving only the midvein.

Recently hatched orangestripped oakworms. Photo: SD Frank

Recently hatched orangestripped oakworms. Photo: SD Frank

Orangestripped oakworms can partially or entirely defoliate trees but often only one or two branches are affected. Even though they are actively feeding now orangestripped oakworms become most obvious later in August when they start crawling down trees and along the ground looking for pupation sites in soil and leaf litter. Also, later in the summer damage becomes more noticeable and people begin to notice frass pellets on their decks and walkways. By that point though they are usually about done feeding for the year so treatment is not warranted.

Late instar orangestripped oakworm surrounded by frass. Photo: SD Frank

Late instar orangestripped oakworm surrounded by frass. Photo: SD Frank

Unlike most pests of ornamental plants, orangestripped oakworms have been fairly well studied. This is thanks to Mark Coffelt and Pete Schultz who studied this critter at Virginia Tech in the 1990’s. They studied the life cycle, damage, parasitoids, and developed a sampling plan, aesthetic injury level, and threshold.

The authors (Coffelt and Schultz 1990) used a survey with photographs of trees with 15, 25, 50, 75, or 100% defoliation. Most respondents (70%) were willing to accept some defoliation and 42% responded that 25% defoliation was aesthetically acceptable. Moreover, they found that 25% defoliation did not reduce root starch reserves which is a measure of tree vigor.

To determine which trees may exceed the aesthetic threshold, Coffelt and Schultz (1993) developed a threshold based on egg masses per tree. They found 5m trees with 12 cm dbh will reach 25% defoliation if with one egg mass and 100% defoliation with 4 egg masses. Larger trees with dbh of 19 cm, 26 cm or 35 cm would require around 5, 7, and 9 egg masses respectively to reach the aesthetic injury level of 25% defoliation.

Recently hatched egg cluster. Dark eggs contain parasitoids. Photo: SD Frank

Recently hatched egg cluster on the bottom of an oak leaf. Dark eggs contain parasitoids. Photo: SD Frank

Orangestripped oakworm eggs are typically laid on terminal ends of lower branches. Therefore, by looking up at the undersides of lower leaves you can get a decent count of the masses of yellow eggs. Soon after egg hatch you can estimate the number of egg masses that hatched by the number of damaged branches. Since young caterpillars feed in groups, one branch with one group of damaged leaves probably resulted from a single egg mass. Thus, based on the threshold, if you went out now and saw a 12 cm dbh tree with 4 separate areas of defoliation (4 egg masses hatched) you might expect near 100% defoliation later in the summer and consider some form of management now if the tree is a key component of the landscape or has experienced other stresses that could weaken its recovery.

Group of orangestriped oakworms feeding on a branch. Photo: SD Frank

Group of orangestriped oakworms feeding on a branch. Photo: SD Frank

Management of these caterpillars, and other gregarious species, can be as easy as pruning. Since the larvae all feed together you can prune out infested branches and nearly stop further defoliation. On large trees with large populations pruning may be impossible or unfeasible. In this case, registered insecticides may be used to reduce damage and frass. Again though, in late summer when larvae are full grown the damage is done so insecticide applications are probably of little value.

Defoliated branch with petioles and mid-veins remaining. Photo: SD Frank

Defoliated branch with petioles and mid-veins remaining. Photo: SD Frank

Orangestripped oakworms feed on most oak species and can also occasionally damage maple, birch, and hickory trees. Even though they look well-armored with black spines and frontal horns they do not sting and are safe to handle. We are lucky to have so much information on this pest to help with management decisions. Understanding the biology and aesthetic injury thresholds of other key pests would really improve IPM of urban landscape plants.

References:
Coffelt, M.A. and P.B. Schultz. 1990. Development of an aesthetic injury level to decrease pesticide use against orangestriped oakworm (Lepidoptera: Saturniidae) in an urban pest management project. Journal of Economic Entomology 86: 1512-1515.
Coffelt, M.A. and P.B. Schultz. 1993. Quantification of an aesthetic injury level and threshold for an urban pest management program against orangestriped oakworm (Lepidoptera: Saturniidae). Journal of Economic Entomology 86: 1512-1515.
Coffelt, M.A., P.B. Schultz. and D.D. Wolf. 1993. Impact of late-season orangestriped oakworm (Lepidoptera: Saturniidae) defoliation on oak growth and vigor. Environmental Entomology 22: 1318-1324.
August 4th, 2015|Categories: Uncategorized||

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

Emerald ash borer adult. David Cappaert, Michigan State University

Emerald ash borer adult. David Cappaert, Michigan State University

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

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

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

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

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

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

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

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

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

New and Updated Insect Notes for Pests of Ornamental Plants

Old Insect Note

Old Insect Note

Maybe you have already found the relatively new Extension Resource Catalog. This is a huge effort by Extension to modernize  fact sheets and other information resources. Instead of every department, or even every program, having its own fact sheet design and delivery format (web?, pdf?, print?, fax?) all the resources will look the same and reside in the same place. The interface makes it easy to update so the resources will be (should be) more current. They are also printable. Yeah for Extension.

With help from the great folks in Extension IT I am gradually getting the Insect Notes for Pests of Ornamental Plants moved from their current home to the new Extension Resource Catalog. You can find several Insect Notes already present like Gloomy Scales, Greenstriped Mapleworm, Japanese Maple Scale, and Maple Spider Mites.

New Insect Note

New Insect Note

When you get to the main Extension Resource Catalog you will find every resource from every department and county all listed together. Don’t fret. On the left bar you can select resources by topic, like Commercial Horticulture, Nursery & Turf, or by Department. This will help narrow down the list. Of course you can also use the search bar. I think this is an overdue, but great, advance in NCSU Extension delivery. Please be patient as I transfer the 200 Insect Notes on ornamental pests into the new system. If there are Insect Notes you would find particularly useful please let me know.

July 9th, 2015|Categories: Greenhouse IPM, Landscape IPM, Nursery IPM, Uncategorized|Tags: |