THE ASIAN AMBROSIA BEETLES
crassiusculus (Mot.), Coleoptera, Scolytidae.)
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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
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
by: Dr. Beverly Sparks,
Identifying the Injury.
- In southern pines, Live oaks
and other hardwoods, large piles of a fine white granular dust accumulate
below the entrance holes or at the base of standing trees. In lumber, the
galleries are darkly stained. The galleries produced by these beetles are
produced just underneath the bark.
Boring dust at base of
in the sap wood
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.
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
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
M. Choate, University of Florida
Links to other related articles:
Oak Borer - Slime Flux
- Hypoxylon Canker -
Wood Boring Insects -
Oak Bark and Ambrosia Beetles -
Pests, Southern Region -
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,
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.
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.
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.