Managing cicadas in nurseries and landscapes

For folks in western parts of the state you may have periodical cicadas in your nursery or landscape.  Of course this will depend on a number of things including the habitat surrounding your nursery.  Areas with a lot of suburban development may have fewer than less disturbed areas.

Cicadas cause damage to trees when they lay eggs in branches.  They use a knife-like

Oviposition scar. Photo: Tim Tigner, Virginia Department of Forestry,

Oviposition scar. Photo: Tim Tigner, Virginia Department of Forestry,

ovipositor (egg inserter) to insert eggs into thin tree branches.  This causes slits in the branch that could be 6 inches long or more.  This long scar reduces plant aesthetic value but also weakens branches. Scarred branches usually break and fall to the ground or break and remain hanging in the tree but turn brown.

We have found that imidacloprid reduces oviposition in landscape trees.  (read the full publication) Females detect the insecticide with their ovipositor so treated trees have fewer scars and the scars are much shorter.  Thus branches do not

Flagging branches. Photo: Linda Haugen, USDA Forest Service,

Flagging branches. Photo: Linda Haugen, USDA Forest Service,

become as weak so there is less flagging.  This is not to say you should treat every tree with imidacloprid.  Most landscape trees over a few feet tall can withstand losing many branches with no negative effects on health.  Even nursery stock could survive losing branches but may need corrective pruning. Nursery stock can be pruned to remove scarred branches.

Trees that are very valuable could be protected with mesh netting to keep cicadas off (read the full publication). This may apply to specimen trees in landscapes or to particularly expensive nursery trees. Japanese maples may be one species where shape is very important and it would be worth protection of some sort.

Hibiscus sawfly damage

In Georgia last week I found severe damage by hibiscus sawfly.  Larvae and adults were

Adult hibiscus sawfly. Photo: S.D. Frank

Adult hibiscus sawfly. Photo: S.D. Frank

present on the plants I surveyed. The adults are active throughout the summer. The larvae feed on hibiscus and related plants. The larvae skeletonize leaves when they are young but quickly defoliate plants as they grow. Contact insecticides such as bifenthrin and orthene will kill larvae. Other insecticides such as spinosad, acetamiprid, azadirachtin and

Damage caused by hibiscus sawfly larvae.  Photo: S.D. Frank

Damage caused by hibiscus sawfly larvae. Photo: S.D. Frank

other listed here can also be used. They are not caterpillars so be sure to look for sawflies specifically on the label of the product you select. More information on this critter is here.

Red headed flea beetles active in nurseries

Redheaded flea beetles, Systena frontalis, have become a serious pest of nursery stock

Redheaded flea beetle on Itea. Photo: Greg Bryant, NCSU

Redheaded flea beetle on Itea. Photo: Greg Bryant, NCSU

over the past several years.  They are an especially damaging pest because they feed on roots and leaves.  They overwinter as eggs in the soil.  Larvae hatch in spring and begin feeding on roots. The larvae are elongate and creamy-white.  Heavy infestations may reduce root mass or girdle plants.  Adult redheaded flea beetles are small, shiny black, beetles with reddish to dark colored head and long antennae.  They are about 1/16 of an inch long and, as the name suggests, jump when they are approached. There are at least two generations in Delaware and may be more in North Carolina.

We found adults and adult feeding damage this week.  The favored hosts are Itea, hydrangea, forsythia, and knockout roses.  Adult management has been frustrating for growers who find that even frequent insecticide applications do not reduce adult abundance and damage to acceptable levels.  Part of this has to do with not controlling larvae since even if you kill all the adults present in a crop (which you won’t) more adults are emerging from the soil every day. Research thus far in Delaware and grower reports indicate that Talstar, Sarfari, and Flagship provide good efficacy as foliar applications but do not have long residual activity. Read more in this fact sheet from Dr. Brian Kunkel

in Delaware.

Pyracantha pest problems

This week we noticed some major pest infestations on pyracantha bushes around campus.  The most noticeable is woolly apple aphid infestations.  These produce cottonyIMAG1831 fluff along the branches. When you brush away the fluff (really it is wax the aphids produce) you will see hundreds of pink or grey aphids crawling around.   Woolly apple aphids have been out for a month or so now but are becoming very noticeable now.  Infestations for multiple years produce large leafless patches on bushes.  The aphids cause galls to form on branches and branches become black from sooty mold. Soap or oil should provide some control but other aphid management information is here.

The other pyracantha pest that just started hatching is hawthorn lacebug.  The major

IMAG0968landscape plants that hawthorn lacebugs feed on are pyracantha, service berry, and cotoneaster.  Lacebugs management information is here. Imidacloprid will kill both pests but should not be used on plants that are flowering or that will flower soon due to negative effects on pollinators.

Another bug that pyracanthat seems to be ‘infested’ with are lady beetles.  These are predators and attracted by aphids and lacebugs but I have found pyracantha bushes with dozens of larvae and pupae on them.

Cankerworms as food…..

…for other animals of course.  Birds eat a lot of cankerworms and may even have more DSC00427chicks or greater chick survival when there are so many caterpillars to eat.  This week I have found arthropod predators chowing down.  I found several species of ants carrying cankerworms back to their nests or wrestling with them on the sidewalk.  The ant pictured could have used some help getting the cankerworm up over a curb.



One of my favorite groups of predators, carabid beetles, also seem to be taking advantageDSC00433 of the bounty. I have seen more carbids in the genus Calosoma this year than ever before. Calosoma species are forest dwellers (and urban campus dwellers apparently) that eat caterpillars. One species, Calosoma sycophant, was imported from Europe to try and combat gypsy moth.  Unfortunately, no one told them and they eat whatever caterpillars come along. Gypsy moth continues to be a problem.  Anyway they are big and beautiful and voracious predators.

Spiders have also had a pretty easy time this year. This jumping spider was on the railing and had just captured a cankerworm when I started tormenting it.  I have also seen wolf

Jumping spider with cankerworm. Photo: S.D. Frank

Jumping spider with cankerworm. Photo: S.D. Frank

spiders on tree trunks and on the ground eating cankerworms.

Just remember these predacious arthropods (and baby birds if thats your thing) when you see defoliated trees (which will be fine by the way) or  when you’re tired of having caterpillars in your hair (which will also be fine).

Watch for spirea aphids

This weekend I found bushes with tons of spirea aphids on them.  In some cases 50% of

Aphids on spirea in full sun. Photo: S.D, Frank

Aphids on spirea in full sun. Photo: S.D, Frank

the growing tips had clusters of the light green aphids.  The plants most affected seemed to be in full sun. Shaded ones had fewer.  Heavy infestations on landscape or nursery plants can cause twisted or deformed foliage.  Especially in the landscape predators may take care of them pretty quickly.  In the nursery though you may not be able to wait, or risk damage, if you are moving plants out for sale.  In many cases horticultural oil, soap, or even a stream of water is enough to reduce populations of these exposed aphids. Other insecticides can be found on the aphid note.

Aphids on roses

I found a severe infestation of aphids on some landscape roses this week. Aphids this early covering the buds could reduce the number and quality of blooms. I am not sure why the aphids attacked this bush so severely and so early  but folks should be on the lookout. I  have also seen a lot of other aphids this week on maples, Japanese maples, and other plants. You can check the aphid insect note for more management information. Image

Ambrosia beetles emerging en masse

After a cool spring I was beginning to think the ambrosia beetles would never come out.  Yes, we have had a few detections around the state that I posted before but we have


Characteristic frass toothpick extruded by ambrosia beetles as they bore into trees. Photo: S.D. Frank

captured very few in our traps.  In experiments we are conducting no trees have been attacked no matter how unhealthy or stressed. Until today.  Yesterday I got a report from the foothills that the first granulate ambrosia beetle was captured. It was 80 degrees in Raleigh yesterday and our traps filled up.  This morning we had two attacks at our experimental nursery on Lake Wheeler road.  I image when we check tomorrow there will be even more.

Management of ambrosia beetle damage requires pyrethroid applications every 3 weeks to the trunks of trees. Ambrosia beetles usually attack below the first scaffold branches so you do not need to spray the canopy. Most folks apply permethrin with an airblast sprayer. We have tested a manual sprayer and fold more complete, even coverage.



Dual-nozzel sprayer we made to spray trees for ambrosia beetles. Photo: S.D. Frank.

You can read about it in a recent paper.  The manual sprayer has two opposing nozzles to quickly cover tree trunk with insecticide. It takes a little longer but uses less insecticide and reduces drift and secondary mite outbreaks.

Hot in the City: urban heat and the future of trees

In this guest post our PhD student, Emily Meineke, discusses her new paper in PLoS One and the the city life of plants, pests, and people…..

Most people live in cities. We walk between tall buildings and eat food grown thousands of

Emily hard at work counting scales in climate chambers. Photo by Becky Kirkland/NC State University Communications

Emily hard at work counting scales in climate chambers. Photo by Becky Kirkland/NC State University Communications

miles away. Urbanization brings big changes, and these changes have consequences—good and bad—for the creatures live with us, from microbes to mammals. Two big questions are: How do we change the species around us, and how do they change us? Now that most people live in cities, urban species are at the center of these questions.

More so than in any other ecosystems, humans engineer the conditions in which other species live in cities. This engineering includes intentional consequences (streets and their traffic) but also unintended ones, such as the urban heat island effect.

Imagine what cities used to look like before industrialization: a cart, a horse, and a dirt road. Imagine that cart becomes a car. Then the dirt under that car becomes a sidewalk, and the wooden shop beside the car becomes a modern building. Every part of the built environment that was wood or some other soft material becomes plastic, cement, or metal. Most of the materials in cities now are impermeable, meaning water can’t get in, and heat gets trapped. Cities are seas of man-made hardscape that hold in heat during the day and slowly release it at night, so that when surrounding rural areas are cooling off for the evening, cities are still heating themselves up from everywhere. This excess heat, the urban heat island effect, is changing the urban fauna, including us.

Thermal map of the Raleigh urban heat island.

Thermal map of the Raleigh urban heat island.

Hotter cities disadvantage certain groups of our own species that are sensitive to high temperatures. They can also kill some plants, whether via drought or the direct effects of heat. However, the vast majority of animals that live around us need heat from outside their bodies to survive. Some urban warming could be a good thing for some of these species, including some insects, spiders, and roly polies, just to name a few.

In this big story, I study one small but (I think) consequential piece: how urban warming affects scale insects (photo), tree pests closely related to aphids that insert their straw-like mouthparts into trees and suck out their phloem. Sometimes they kill street trees, but more often they weaken them.

My new research, published in PLoS One, shows that urban warming causes scale insects

Oak lecanium scale on willow oak twigs. Photo by Becky Kirkland/NC State University Communications

Oak lecanium scale on willow oak twigs. Photo by Becky Kirkland/NC State University Communications

to become more abundant in cities. Warm a street tree and the scale insects on it become much, more dense. This happens even in the lab, though the scale insects from warm trees seem better able to take advantage of the heat. It may be they have evolved so as to like it hot, or at least hotter. Warming-driven scale insect outbreaks are likely to be bad news for urban plants. And because urban plants remove pollutants from the air and cool cities, they might be bad news for us too.

Knowing what urban heat does to pests can help us predict changes as global temperatures climb. Overall, between killing or weakening trees via drought and pest insects and causing human health issues, urban warming seems like bad news.

This is not to say I begrudge the scale insects. They do what they have long done; they suck (plant juices). They are fascinating and poorly understood, and I plan on spending the next years of my life figuring out their mysteries. The good news is, we know a lot about how to mitigate the effects of urban warming. Plant a tree. Paint your roof white. Or, better yet, plant a tree on your roof. But when you do, keep an eye on the scale insects and tell me what you see. They will be there, I guarantee you. They always are – the real question is how abundant they will be, whether or not they have prospered in the luxuriance of urban warmth.

There will be more to this story (I’m just starting my thesis), so stay tuned. Or if you aren’t the sit and wait type, go outside and start looking at what else is going on in the ecology of the city. Scales are just the tip of the urban life-berg. There are beneficial microbes living inside the scales. Sometimes the scale may be the unlucky victim of a parasitoid wasp. Go deeper and you might find that the offspring of that parasitoid wasp growing inside the scale could also be unlucky, themselves the host of a hyper-parasitoid wasp. No one said urban life was simple, it is just relevant and more so every day.

This work was supported by a grant from the USGS Southeast Regional Climate Science Center to RRD and SDF. RRD was also supported by NASA Biodiversity Grant (ROSES-NNX09AK22G) and an NSF Career grant (0953390). SDF was also supported by grants from USDA Southern Region IPM (2010-02678), North Carolina Nursery and Landscape Association, the Horticultural Research Institute, and the USDA IR-4 Project. EKM was also funded by the NCSU Department of Entomology, and an EPA STAR Fellowship.

The research described in this paper has been funded wholly or in part by the United State Environmental Protection Agency (EPA) under the Science to Achieve Results (STAR) Graduate Fellowship Program. EPA has not officially endorsed this publication and the views expressed herein may not reflect the views of the EPA.

The project described in this publication was supported by Grant/Cooperative Agreement Number G10AC00624 from the United States Geological Survey.  Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USGS

Granulate Ambrosia Beetles active!

Nurseries throughout the state have reported Ambrosia beetle captures in traps and attacks on trees. Granulate ambrosia beetles emerge in early spring and attack many deciduous trees.  They have been reported to damage over 100 species of trees.  However, species most commonly reported to be damaged in North Carolina nurseries are styrax, dogwood, redbud, maple, ornamental cherry, Japanese maple, and crepe myrtle and magnolia. The best way to prevent damage is to apply a pyrethroid such as permethrin or bifenthrin to tree trunks. Beetles generally attack below the first scaffold branches so spraying entire trees is unnecessary and can lead to mite outbreaks. An insect not is available here.