THE ASIAN AMBROSIA BEETLES

 

Adult   (Xylosandrus crassiusculus (Mot.), Coleoptera, Scolytidae.)

Importance. - Ambrosia beetles were named for those species that farm ambrosia fungus (Ambrosiella spp.). The females excavate tunnels (galleries) in wood; some species select living, but often stressed, trees, some use only recently deceased trees. 

An ambrosia beetle has a specialized hollow under its thorax called a mycangium. The excavated gallery is planted with asexual fungal spores (clones) carried in the mycangium from the beetle's mother's gallery. The beetle tends her garden and her offspring feed strictly on the fungus. Since they are social, the beetles mate among the siblings.

Some ambrosia fungi are only known from beetle galleries and it is believed that those associations are obligate--the fungi cannot survive without the beetle farmers. Generations of closely related beetles farm generations of cloned ambrosia fungus.

For the ambrosia fungus to survive and be of use to the beetle, it must be farmed inside wood that has good moisture content. Ambrosia beetle attack on recently cut trees can greatly reduce the strength and value of lumber. After trees are cut, the lumber must be quickly dried and milled to prevent an infestation.

Identifying the Insect. - The adult beetles are elongate, about 1/16 inch long, and stout bodied and dark reddish brown, and usually have sharp spines at the rear. The males are much smaller, have a more hunch-backed appearance and are flightless.

                                                                Asian ambrosia beetle larvae and eggs in gallery
                                                                                      Photo by: Dr. Beverly Sparks,
                                                                                      UGA Extension Entomologist

                         

Life Cycle: - The platypodids "flat-footed" or ambrosia beetles comprise about 1,000 species in the subfamily Platypodinae. The genus Platypus has seven species in North America. They are tiny social beetles, most are female. They are haplodiploids; females hatch from fertilized eggs and are diploids (paired chromosomes), males are haploids (single set of chromosomes) hatching from unfertilized eggs. Ambrosia beetles bore into wood. Female beetles excavate galleries deep into the wood of twigs and branches, pushing out strings of boring dust which will resemble tooth picks. These protrusions can be up to an inch in length, often with several hundred on an individual tree. Afterwards, the beetles cultivate an ambrosia fungus which has been carried into  the gallery by the adult. Females then lay eggs which hatch into legless larvae that develop through several stages (instars) before pupating. Both the adults and the larvae feed on the fungus rather than the host plant. Female beetles remain with their brood until they mature. Newly emerged adult beetles mate with their offspring before leaving the gallery. Flight activity apparently occurs throughout the year, with higher activity in March.      

Adult female Adult male   Thomas H. Atkimson, University of Florida

TINY BEETLE WREAKS HAVOC ON TEXAS ORNAMENTAL TREE NURSERIES http://agnews.tamu.edu/dailynews/stories/ENTO/Apr2804a.htm

Habitat and Food Source(s): - Mouthparts are for chewing. This beetle attacks 126 plant species including pecan, peach, plum, cherry, persimmon, Red oaks, Live oaks, Shumard oak, Chinese elm, sweet potato and magnolia. Infestations start with a female beetle boring in to a twig, branch or trunk of a host plant. Host material can range from approximately 0.8 inch to 11.8 inches in diameter. This beetle will attack seemingly healthy trees. Attacks generally occur on the trunk of the host plant. Immature stages can be found by splitting open infested twigs and branches.

Biology. - The adults and larvae do not feed on the wood but on a fungus the beetles carry into the tree and culture in the galleries. The adults bore into sapwood or heartwood of logs and lumber, making pinsized holes which are stained by the fungus. The females lay eggs in small clusters in the tunnel, and the developing larvae excavate tiny cells extending from the tunnel parallel to the grain of wood. There may be several generations a year. Timber is not attacked unless the moisture content of wood is at least 48 percent. Seasoned lumber is never infested.

Control. - There is little in the line of pesticides for the homeowner to control the beetle. It has been said, for control to be effective you must hit the beetle on the butt as she bores into the wood. Chlorpyrifos (Dursban ®) or lindane have not been very effective in control, there are few registered chemical  alternatives. A possible solution worth trying would be putting a soil drench with Merritt ® in the ground in the hopes that its systemic effect would kill the larvae.  Badly damaged or dying plants (plants with 15 - 20 or more holes) should be removed and the wood destroyed or chipped. Plants with fewer holes should be watched closely and watered properly. Any branches that show signs of wilting should be removed, they will not recover.

Homeowners may try Pyrellin, Pyrenone or a landscape spray containing a pyrethroid such as permethrin or cyfluthrin, but may have to treat weekly while beetles are active. Keep trees healthy and avoid any unnecessary tree stress (drought, injury, nutrition, etc.). Check trees frequently beginning early March and treat accordingly.

  A Field Guide To Common Texas Insects  -  Order To Day -  Click on Image.

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by Scenic Hills Nursery nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any, chemical. For assistance, contact a local arborist or an agent of the Texas Cooperative Extension Service in your county.

Frass tubes produced by Asian ambrosia beetle.
Photo by W. O. Ree, Jr.

 

      
dorsal and lateral view  Ooze bleeds out of canker wound

                              Paul M. Choate, University of Florida 

   

 Links to other related articles:  Red Oak Borer - Slime Flux - Hypoxylon Canker - Tree Decline

                 1)    Wood Boring Insects    -   http://entowww.tamu.edu/extension/bulletins/b-5086.html

                 2)   Oak Bark and Ambrosia Beetles   -    http://www.greenbrae.org/news/art_UC_Jan00.html 

                 3)   Forest Pests, Southern Region  - http://www.forestpests.org/southern/index.html

  

Ambrosia Tracks:  The ambrosia beetle bores into the sapwood of dying or recently felled trees. The ambrosia beetle is very small, approximately 1 to 2 mm in length. While the ambrosia beetle bores into the wood, it does not feed on wood. The ambrosia beetle feeds on the ambrosia fungus that is cultivated in the newly bored tunnels. But there are instances that the ambrosia beetle increases the value of the lumber. Sometimes a second fungus is introduced into the gallery. This fungus stains the grain of the wood. The fungal stains increase the wood's decorative value especially in birch, oak, and maple. If only a few beetles infest the wood, the naturally stained wood makes beautiful furniture, bowls, and boxes.

The ambrosia fungus stains the tunnels and surrounding wood. The stained paths are visible in turnings of wood that were formerly home to the ambrosia beetle.

 

WANTED  Asian Ambrosia Beetle, Xylosandrus crassiusculus An insect pest of fruits, nuts and woody ornamentals is spreading across Texas and the Texas Agricultural Extension Service is asking for your assistance. If you observe an infestation as shown in the picture, please call the number below or your county Extension agent. IF FOUND CALL: (409) 845-6800, Notify: Bill Ree, Extension Agent-Entomology, and Leslie Hunter, Extension Assistant, The Texas A&M University System.  OR YOUR COUNTY EXTENSION OFFICE.