Orange-striped oakworms make yearly appearance

This is a quick field note by PhD student Emily Meineke.

For the last few weeks, orange striped oakworms have been raining on my head as I work in the trees. They also drop a lot of

 

 

Large oakworms eat entire leaves except for the mid vein. Photo: EK Meineke

Large oakworms eat entire leaves except for the mid vein. Photo: EK Meineke

poop (entomologists call it frass) which is one of the major complaints by homeowners. Orange-striped oakworms congregate on branches to feed every year in late summer but usually do not cause enough damage to warrant treatment.

Young oak worms cause damage called 'window panning' in which they eat the surface of leaves and feed between tiny veins. Photo: EK Meineke.

Young oak worms cause damage called ‘window panning’ in which they eat the surface of leaves and feed between tiny veins. Photo: EK Meineke.

Young orangestriped oakworms are often light in color and darken as they get older. I have found some parasitized individuals, which means natural enemies are doing their part to reduce oakworm outbreaks. Caterpillars also make great food for birds. We have posted previously about orange-striped oak worm biology and management if you want more information.  

Large caterpillar poops around the base of a tree. Photo: SD Frank

Large caterpillar poops around the base of a tree. Photo: SD Frank

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New ambrosia beetle marching across the US

Nursery growers have been struggling with ambrosia beetles for decades. In the southeast it is

Scopes-eye view of camphore shot borer fresh from a trap mixed in with granulate and other ambrosia beetle species. Photo: Andrew Ernst, NCSU.

Scopes-eye view of camphore shot borer fresh from a trap mixed in with granulate and other ambrosia beetle species. Photo: Andrew Ernst, NCSU.

primarily the granulate ambrosia beetle, Xylosandrus crassiusculus. In the Northeast and Midwest the predominate species is Xylosandrus germanus. These are tiny beetles that make tiny albeit lethal holes in trees. 

In the past several years a new species has been detected in several states including Florida, Tennessee, North Carolina, and just last month Virginia. This is the camphor shot borer, Cnestus (used to be Xylosandrus) mutilatus, and it is BIG. At least by ambrosia beetle standards this one makes holes as big as a pencil instead of then tiny 2mm holes made by other species. You can find out all about it in a thorough publication from University of Tennessee.  

We trap at 5 -10 nurseries every year around Johnston County, North Carolina. In 2011-2013 we captured 1 or 2 camphor shot borers each year. This year we captured about a dozen from at least 3 different nurseries. So it is here to stay and will probably become more of a problem over time. 

Camphor shot borer in a twig photographed by Matt Bertone, NCSU.

Camphor shot borer in a twig photographed by Matt Bertone, NCSU.

Retailers to label neonic-treated plants

Scientific American is reporting from Reuters that Home Depot, BJ’s Wholesale, and other smaller retailers will soon require vendors to label plants that have been treated with neonicotinoid insecticides. Neonicotinoids are among the most commonly used insecticides on ornamental crops and all crops. This class of chemicals includes imidacloprid, dinotefuran, thiamethoxam, acetamiprid, clothianidin, and others. Controversy around neonics revolves around their potential to harm bees and other pollinators. Like most insecticides, neonics are acutely toxic to bees on contact. Since neonicotinoids move systemically within plant tissue they can also contaminate flower pollen and nectar that bees consume. Though this can negatively affect individual bees the effects on bee populations is not yet known (and very hard to measure).  Information about this was recently reviewed in two extension publications and a scientific paper. Of course there is no news that these outlets will stop selling neonicotinoids to consumers. Nursery and greenhouse growers who produce crops for retail outlets should start figuring out alternative insecticides as this trend is likely to spread.

Japanese maple scale

Japanese maple scale, Lopholeucaspis japonica , is active now and much of the summer. It is a small, oystershell-shaped, armored scale introduced to the U.S. from Asia. Japanese maple scale is found in several eastern U.S. states, including CT, DE, GA, KY, MD, NC, NJ, PA, RI, TN and VA, as well as Washington D.C.. Japanese maple scale has a wide host range that in addition to maples (e.g., Japanese maples, Red maples, Paperbark maples, and sugar maples), includes Amelanchier, Camellia, Carpinus, Cercis, Cladrastis, Cornus, Cotoneaster, Euonymus, Fraxinus, Gledistia, Ilex, Itea, Ligustrum, Magnolia, Malus, Prunus, Pyracantha, Pyrus, Salix, Stewartia, Styrax, Syringa, Tilia, Ulmus, Zelkova, and others.

Brian Kunkel, University of Delaware, Bugwood.org

Brian Kunkel, University of Delaware, Bugwood.org

Although the lifecycle of this pest has not been fully examined, two generations a year are expected in the mid-southern U.S. First generation crawlers emerge in mid-May, and the second generation in early August  but there may be more. Management efforts are complicated by the extended crawler emergence that results in first and second generational overlap. Thus, the most recent sample we received had every stage – egg to adult- present at the same time.

Adult scales and crawlers are very small and most readily observed on bark of dormant deciduous host plants, but can also be found on foliage. The waxy coating on the body of male Japanese maple scales is white and females, eggs, and crawlers are lavender. The most work on this scale has been done by Paula Shrewsbury and Stanton Gill at the University of Maryland. There is also information on JMS and other maple pests in our new book here: http://ecoipm.com/extension/extension-resources/

A link to the UMD fact sheet is here: http://ipmnet.umd.edu/nursery/docs/JapaneseMapleScale-UMD2011.pdf

 

Maple spider mites

Maple spider mites (Oligonychus aceris) are common and damaging pests of maple trees throughout the Eastern United States. These spider mites overwinter on the trunk and

Adult maple spider mite. Photo: AG Dale

Adult maple spider mite. Photo: AG Dale

branches of maple trees and migrate to the underside of leaves in the spring. Once there, they use their mouthparts to pierce leaf cells and feed on cell sap. This causes fine flecking called stippling and eventually leaves turn gray or brown after heavy feeding. Maple spider mites have multiple generations per year which enables them to become quite abundant during a single season. These pests are a more serious problem in nurseries due to the close proximity of potted trees and applications of broad spectrum insecticides like permethrin. For example, our research has shown that applications of permethrin targeting ambrosia beetles can wipe out natural enemies and result in secondary maple spider mite outbreaks. Maple spider mites can also be abundant on landscape trees. Trees in parking lots and along roads are most likely to be infested.

Maple spider mite egg attached to tree bark. Photo: AG Dale

Maple spider mite egg attached to tree bark. Photo: AG Dale

A hand lens or stereo microscope is necessary for correct identification of these mites but damage is a good indicator of infestation. They are dark brown or red with hairs along their backs and have eight legs while some immature forms exhibit green coloration and have six legs. Red eggs of these mites can be found on tree limbs and yellow or clear eggs can be found on leaf surfaces. Treatment for these pests includes foliar applications of acaricides. Maple cultivars differ in susceptibility to maple spider mites and other maple pests like leafhoppers. A chapter in a recent free ibook IPM for Select Deciduous Trees in Southern Nursery Production describes more

Maple spider mite damage. Photo: AG Dale

Maple spider mite damage. Photo: AG Dale

about management of maple pests and other tree pests. A recent article in Nursery Management and a fact sheet describes mite biology and management. This time of year trees may not be sold until fall so the condition of leaves is not as much of an issue. On landscape trees mite damage reduces fall color and summer color because leaves are gray, yellow, or brown instead of green.

 

Pittosporum psyllid in NC

Another new pests has turned up around Wilmington, NC. This one on an exotic

Adult Cacopsylla tibiae and characteristic damage to pittosporum. Photo: Matt Bertone, NCSU PDIC.

Adult Cacopsylla tibiae and characteristic damage to pittosporum. Photo: Matt Bertone, NCSU PDIC.

ornamental plant Japanese pittosporum (Pittosporum tobira). The pest, Cacopsylla tobira, is a sucking insect called a psyllid.  Psyllid feeding generally causes deformed leaves. The most common or well-known psyllid in ornamental plants is probably the boxwood psyllid that causes cupped leaves at the end of boxwood twigs. Cacopsylla tobira has only been reported from California in the US. Thus not much is known about the biology, management, or damage of this pest. California has a note on psyllids that infest various crops if you would like to know more about this group. Please take note of strange damage to pittosporum and send suspicious samples to the Plant Disease and Insect Clinic.

Adult Cacopsylla tibiae. Photo: Matt Bertone, NCSU PDIC.

Adult Cacopsylla tibiae. Photo: Matt Bertone, NCSU PDIC.

Euonymus scale

Somehow I got this far in the season without posting anything about euonymus scale.

Euonymus scale

Euonymus scale on a heavily infested leaf. Photo S.D. Frank

Maybe because this is the first year I have not been conducting research on it or writing papers about it. Euonymus scale has three generations per year in North Carolina the first of which occurs around May. It is best to treat euonymus (or any) scale in the crawler stage. So if you forgot in the spring or didn’t get sufficient control (or were waiting for an alert from me) you still have a chance. Crawlers are active at sites on campus and in Raleigh neighborhoods. In the first generation crawlers come out all at once but become less synchronized in second and third generations. Thus you may find all developmental stages present at this time. There are a number of products that can be used to treat armored scale. You can read an article in Nursery Management about scale control here. Our research (published here) has found neonicotinoids Safari, Flagship, and TriStar to be very effective and also plant growth regulators Distance and Talus. Note that imidacloprid is not labeled for, or effective against, armored scale. Please check the updated insect note for recommendations http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note15/note15.html