Xyleborus glabratus

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Authors: Ellis, A.M., and A.C. Hodges, University of Florida and Mayfield III, A.E., Florida Department of Agriculture and Consumer Services, Division of Forestry

5198081
Taxonomy
Kingdom: Animalia
Phylum: Arthropoda
Class: Hexapoda (including Insecta)
Order: Coleoptera
Family: Curculionidae
Genus: Xyleborus
Species: X. glabratus
Scientific Name
Xyleborus glabratus
Eichhoff, 1877
Common Names

redbay ambrosia beetle

Contents

Overview

Origin
Xyleborus glabratus is native to India, Japan, Myanmar, and Taiwan.
Life Cycle
Xyleborus glabratus adults are small, 0.08 in. (2 mm) long, slender, cylindrical, and brown-black in color. It is very similar to other members of the genus but the combination of its coloration, glabrous elytra, and abrupt declivity distinguishes it from other species (Mayfield and Thomas 2006). The larvae are white, c-shaped, legless grubs with an amber colored head capsule (Rabaglia 2005). A specialist should be consulted for positive identification of adults and larvae due to their similarity to other species. Adult females construct galleries in the sapwood and inoculate the galleries with a fungus (Ophiostoma sp., vascular wilt pathogen) (Mayfield and Thomas 2006, Rabaglia 2005). The adults and larvae feed on fungi and not on the wood of the damaged host plant. Females are believed to be able to fly 2-3 km in search of a host (Rabaglia 2005). Males are dwarfed, haploid, and flightless and are rarely encountered (Rabaglia 2005). Very little is known about the life cycle and biology of Xyleborus glabratus, but it is assumed to be similar to other species in the genus (Mayfield and Thomas 2006). Most of the life cycle takes place within the galleries, where beetles mate, lay eggs, and young develop.
Distribution
Xyleborus glabratus was first discovered in Georgia in 2002. It has spread to infect redbay and sassafras trees along coastal areas of Georgia, South Carolina and Florida.
Control Efforts
Never transport any part of an infected tree. Cut and chip the infected tree and leave it onsite or at least dispose of it locally. The Don’t Move Firewood campaign is aimed at slowing down the spread of this and other forests pests.

Introduction

Specifically, Xyleborus glabratus is native to India, Japan, Myanmar, and Taiwan, according to reported specimens, but it is suspected that its range is continuous throughout the area (Rabaglia 2005). It was first detected in the US in a survey trap near Port Wentworth, GA in 2002 (Rabaglia 2005). By 2005, Xyleborus glabratus was found to be associated with redbay (Persea borbonia (L.)) and sassafras (Sassafras albidum (Nutt.) Nees) mortality in coastal areas of GA, SC, and FL (Mayfield and Thomas 2006). The Ophiostoma fungus associated with Xyleborus glabratus has also been recovered from pond spice (Litsea aestivalis).

Like other introduced ambrosia beetles, Xyleborus glabratus is suspected to have been introduced in solid wood packing materials such as crates and pallets (Haack 2003). Local spread is potentially caused by the transport of fuelwood, tree trimmings, and other infested wood products from one area to another (Rabaglia 2005). Damage

The principal damage is tree wilt caused by colonization of the xylem cells by the Ophiostoma fungus. Attacked trees exhibit wilted foliage with reddish or purplish discoloration within a section of the crown or throughout the entire crown. The foliage eventually turns brown and tends to remain on the branches. Like other ambrosia beetles, small strings of sawdust (ejected wood fiber) may be present at the point of attack. The fungal infection is evidenced by stained sapwood visible upon removal of bark or in cross sections of the stem.

Description

Xyleborus glabratus adults are small, 2 mm long, slender, cylindrical, and brown-black in color. It is very similar to other members of the genus but the combination of its coloration, glabrous elytra, and abrupt declivity distinguishes it from other species (Mayfield and Thomas 2006). The larvae are white, c-shaped, legless grubs with an amber colored head capsule (Rabaglia 2005). A specialist should be consulted for positive identification of adults and larvae due to their similarity to other species.

Questions concerning identification should be directed to the local cooperative extension service or NPDN diagnostic lab. Diagnosis of host symptoms may be aided by examining digital photographs, but identifying the beetle by images will be difficult due to its small size. An online identification key is available at http://xyleborini.tamu.edu/keys.php, but a specialist should confirm diagnosis. Contact the NPDN for the proper procedures for submitting physical samples because of risks of spreading the beetle and pathogen to new areas.

Life Cycle

Very little is known about the life cycle and biology of Xyleborus glabratus, but it is assumed to be similar to other species in the genus (Mayfield and Thomas 2006). Most of the life cycle takes place within the galleries, where beetles mate, lay eggs, and young develop.

Adult females construct galleries in the sapwood and inoculate the galleries with a fungus (Ophiostoma sp., vascular wilt pathogen) (Mayfield and Thomas 2006, Rabaglia 2005). The adults and larvae feed on fungi and not on the wood of the damaged host plant. Females are believed to be able to fly 2-3 km in search of a host (Rabaglia 2005). Males are dwarfed, haploid, and flightless and are rarely encountered (Rabaglia 2005).

Hosts

In the US, Xyleborus glabratus has been associated with redbay and sassafras (Mayfield and Thomas 2006). The Ophiostoma fungus associated with Xyleborus glabratus has also been recovered from pond spice, indicating that this plant may also be a host. All plants are members of the family Lauraceae and are important to wildlife as browse and fruit plants (Griggs 1990, Gilman and Watson 1994). Redbay also serves as host to larvae of the Palamedes swallowtail (Papilio palamedes (Drury)), which feeds primarily on species of Persea (Mayfield and Thomas 2006). It is possible that Xyleborus glabratus may utilize other members of the Lauraceae as hosts but the host range is presently unknown.

Control

At this time there are no tested or proven treatments for the managing Xyleborus glabratus and its associated fungus (Mayfield and Thomas 2006). Like other exotic species, Xyleborus glabratus will continue to naturally expand its range. In order to reduce its spread, no wood or chips from infested trees should be transported out of the local area.

References

Acknowledgements

We thank Dr. John Foltz, University of Florida, Entomology & Nematology Department and Dr. Mike Thomas, Florida Department of Agriculture & Consumer Services, Division of Plant Industry for their editorial review.

Images from Bugwood.org

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