Management of Wood Boring Insects - Colorado State University

Management of
Wood Boring
Insects
Whitney Cranshaw
Colorado State University

Several Insects Work as Borers
• Some beetle larvae
– Flatheaded borers/Metallic wood borers
– Roundheaded borers/Longhorned beetles
• Some moth larvae
– Clearwing borers
– Carpenterworms
– Pyralid borers
• Some wasp larvae
– Horntails

Flatheaded Borers/
Metallic Wood Borers
Coleoptera:
Buprestidae

Flatheaded Borer

Thinning of the crown is a
common symptom of
flatheaded borer infestation

Pupation occurs under the bark

Photo sequence by David Shetlar, Ohio State University

D-Shaped Exit Hole Produced by Emerging Metallic Wood Borer

Metallic Wood Borer,
Adult Form of a
Flatheaded Borer

Metallic Wood Borer
- Adult form of a
Flatheaded Borer

Some metallic wood
borers have bright
coloration

Four Agrilus sp. Borers
found in Colorado
Top Row - Rose stem girdler (left), Bronze birch
borer (right)
Bottom Row – Honeylocust borer (left), Gambel
oak borer (right)

D-Shaped Exit Hole Produced by Emerging Metallic Wood Borer

Diagnosis – Flatheaded
Borer Injury
• Meandering tunnels produced
under the bark
–Tunnels packed with fine sawdust
• Plant shows decline/thinning
crown
• D-shaped exit holes in bark

Roundheaded Borers/
Longhorned Beetles
Coleoptera:
Cerambycidae

Pine Sawyers

Cottonwood Borer

Banded Alder Borer

Locust Borer

Poplar Borer

Dave Leatherman
Ponderous Borer
Dave Leatherman

Roundheaded Borer

Coarse sawdust expelled from
tree by roundheaded borer

Locust Borer tunneling
Photographs by David Leatherman

Life stages of a
poplar borer
Photograph courtesy John
Ghent/IPM Images

Diagnosis – Roundheaded
Borer Injury
• Tunneling penetrates into
heartwood of the tree
–Riddling, structural weakening
• Coarse sawdust typically
produced
• Oval exit holes in bark

Clearwing Borers
Lepidoptera: Sesiidae

Some Common Clearwing
Borers of Colorado
• Peach tree borer (Prunus spp.)
• Lilac/Ash borer (ash, lilac, privet)
• Currant borer (Ribes spp.)
• Viburnum borer (Viburnum spp.)
• Raspberry crown borer (raspberry)
• Cottonwood crown borer (Cottonwood)

Peach tree borer larval
tunneling in base of plant

Top: Peach tree borer larva
Right: Prolegs on the abdomen,
tipped with hooked crochets, are
characteristic of borers that develop
into moths (Order Lepidoptera)

Small hooks on the underside of the abdomen
(crochets) indicate the larva is a type of moth.
Beetles do not have prolegs on the abdomen
with these hooks.

Upper left: Peach tree borer female
Upper right: Peach tree borer male
Lower left: Pupal skin extruded from
case of silk and wood fragments

Raspberry crown borer larva in base of raspberry

Raspberry crown borer adults –
mimics of yellowjacket wasps

Lilac/Ash borer adult – mimic of a paper wasp

Lilac/ash borer injury to base of ash - exterior

Lilac/ash borer damage to base of ash -interior

Lilac/ash borer larvae

The pupal skin often
extrudes when the
adult emerges

Exit holes are slightly oval, nearly round

Lilac/Ash Borer Mating Pair

Diagnosis – Clearwing
Borer Injury
• Tunneling often concentrated
at the base (root crown) of the
plant
• Tunneling an irregular gouging
• Pupal skins often are pulled out
upon adult emergence

Wood Borer Management
• Optimize conditions for
plant growth
• Sanitation
• Preventive applications of
insecticides

Plant Health Care and Wood
Borer Prevention
• Proper selection of plant material
• Appropriate siting in the landscape
• Good site preparation, planting
conditions
• Provision of adequate
watering
Note: Fertilization can produce mixed effects on borer resistance

Example: Birch and
bronze birch borer

Wood Borers and Plant Stress
• Plant defensive responses are
diminished
–Related to stored photosynthate
and water availability
• Plants may be slightly more
attractive to adults when they
lay eggs

Sanitation and Wood Borers
• Elimination of potential brood
wood
• Prune-out of infested wood
Proper disposal of
infested wood is
important.

Preventive Use of
Insecticides
Treatments are not
available for borers
currently in a plant

Preventive Use of
Insecticides
Timed for Egg
Laying/Egg Hatch
Period!

Evidence of adult
borer activity –
observation of the
adults on plants

Evidence of borer
adult activity –
fresh exit holes

Evidence of
clearwing borer adult
activity – new pupal
skins

For most borers flight
periods can be estimated
Fact Sheet 5.530
(Borers) or Bulletin
506A

Approximate flight periods of
some wood borers
• Lilac/Ash borer
– early May
• Bronzed birch borer (and other Agrilus spp.)
– mid-June
• Poplar borer
– late June
• Peachtree borer
– early July
• Locust borer
– mid-August

Pheromone Traps – A tool for monitoring some insects

Pheromones and Insect
Management
• Pheromones are chemicals used to
communicate between members of the
same species
• Insects use many kinds of pheromones
– Sex
– Aggregation
– Alarm…… and many other things
• Sex pheromones of some moths are
used in pest management

Pheromone trap
data for lilac ash
borer

Active Ingredients of Wood
Borer Insecticides
• Permethrin (Astro, etc.)
• Carbaryl (Sevin)
• Bifenthrin (Onyx, Talstar, etc.)
• Acelypryn
• Imidacloprid
– Soil applied drench

Key Timing Point in Wood
Borer Prevention
Egg Laying/Egg Hatch
(Coincident with adult activity)

Acelepryn
• New class of insecticides –
anthrinilic diamides
– Derivatives of ryania (natural product)
• Activity against most chewing
insects
• Labels being developed for both
turfgrass and woody ornamentals

Acelepryn
• Very low toxicity to vertebrates
–LD50 greater than 5000 mg/kg
• Class 4 – No Caution label
• Protective equipment
–Long sleeved shirt, long pants
–Shoes with socks

Acelypryn labeled use – Lace bugs (soil treatment)

Acelypryn labeled use – Caterpillars (foliar treatment)

Acelepryn labeled use –
clearwing borers (trunk
spray)

Future of Acelepryn?
• Low risk a huge plus
• Soil-applied systemic activity a huge
plus – but poorly understood
• Activity probably includes most leaf
chewing insect groups
• Activity as wood borer treatment very
good (clearwing borers…and others?)

Active Ingredients of Wood
Borer Insecticides
• Permethrin (most available)
• Carbaryl/Sevin (limited availability)
• Bifenthrin (no over-the-counter products at
present)
• Imidacloprid
– Soil applied drench - systemic
insecticide
– Only effective against
flatheaded borers

Imidacloprid for Borers?
Yes…..but

Imidacloprid will not
work well on borers
that are the larval
stage of moths (i.e.
insect order
Lepidoptera)

Peach tree borer larval
tunneling in base of plant

Zimmerman
pine moth
injury

Imidacloprid soil
drenches will work
poorly against
roundheaded borer
larvae that spend little
time in cambium

Imidacloprid soil
drenches will work
poorly against
flatheaded borer
larvae after they have
caused extensive
damage

Imidacloprid soil
drenches may work
well against
flatheaded borer
larvae (aka metallic
wood borers) – if the
plant has not already
been badly damaged

Four Agrilus spp. borers
Dan Herms
Top Row - Rose stem girdler (left), Bronze birch
borer (right)
Bottom Row – Honeylocust borer (left),
Emerald ash borer (right)
David Cappaert

Some Currently Used
Neonicotinoid Insecticides
• Imidacloprid (Merit, Marathon,
Criterian, Provado, Admire - many generics)
• Clothianidin (Celero, Arena, etc.)
• Dinotefuran (Safari)

Relative Water Solubility of Neonicotinoids:
40000
30000
20000
10000
0
Water Solubility (Active Ingredient)
Clothianidin
327 500
Imidacloprid
Slide information courtesy J. Chamberlin
Acetamiprid
Thiamethoxam
2950 4100
39830
Dinotefuran

K oc Values of Neonicotinoids:
0
166
Clothianidin
440
Imidacloprid
Source Data: EPA Pesticide Fact Sheets
267
Acetamiprid
245
Thiamethoxam
26
Dinotefuran

Implications for Dinetofuran
(Safari) Soil Applications
• Dinotefuran requires moist soils
for uptake
– Can move through thin bark
• Uptake into plant is relatively fast
– Ability to control aphids in days
• Persistence in plant much shorter
than other neonicotinoids

Safari trunk sprays have
been developed as a tool to
manage emerald ash borer

Bark Beetles
Coleoptera: Curculionidae
(Scolytinae)

Mountain Pine Beetle
Dendroctonus ponderosae

Western Pine
Beetle
Photograph courtesy of Ladd Livingston/IPM
Images

Friday Seminar – 9:00
What’s Happening in
Idaho’s Forests
Carl Jorgenson
USDA Forest Service

Thousand
Cankers
Disease (TCD)
– An Insect/Fungal
Disease Complex
affecting some
Juglans spp.

A fungus –
Geosmithia
morbida
A beetle – walnut
twig beetle

Jim LaBonte
Walnut Twig Beetle
Pityophthorous juglandis
Jim LaBonte

Adults enter trees
and excavate
galleries

Larval feeding produces a loose network of meandering
tunnels in the cambium

A full grown larva, preparing to pupate.

Teneral adults and pupa, covered with Geosmithia spores

The Pathogen - Geosmithia morbida

Geosmithia is
introduced into
wounds made by
walnut twig beetles

Growth of the fungus beyond the inoculation site
creates a dead region (canker) in the cambium.

Multiple cankers produce girdling that seriously
restricts movement of nutrients.

Flagging symptoms
emerge in end
stages of 1000
cankers on black
walnut

Foliage wilting may occur rapidly on TCD-compromised limbs

Crown symptoms July 2009 – Tree died in 2010

June 2008
September 2008
June 2009

Walnut twig Death beetle exit holes by TCD – Working
Hypothesis
• Girdling from cankers (and bark beetle
tunneling) restricts movement of
nutrients.
• Trees weaken as stored energy
reserves become depleted.
– External symptoms develop in end stages
of infestations
• Trees ultimately die from energy
depletion.

Symptoms of Thousand
Cankers Disease
develop following
sustained introductions
of Geosmithia by walnut
twig beetles in
susceptible hosts.

Origin of Thousand
Cankers Disease

Great picture by Jim LaBonte,
OR Dept. Agriculture!
The walnut twig beetle
was originally described
(1928) from Arizona
walnut, Juglans major.
Original collections of the
beetle were made in 1896.

Published distribution of Arizona walnut

Arizona walnut (Juglans major) – Host associated with
original descriptions of the walnut twig beetle

Arizona walnut is a common species found in canyons
and along riverways

In 2008-2009 surveys, walnut twig beetle was repeatedly
found in Arizona walnut at several sites in NM and AZ

Walnut twig beetle in AZ walnut
functions as a “typical”
Pityophthorus species of twig
beetle. Attacks are normally
limited to small diameter
branches and function as a
form of natural pruning.

Progression to fullblown
Thousand
Cankers Disease has
not been observed in
AZ walnut.

Geosmithia morbida is
also likely to be a native
fungus.

The Geosmithia fungus
is has been found
consistently
associated with the
tunnels and frass of
walnut twig beetles –
regardless of Juglans
spp. or site of
collection.

Canker formation in
black walnut
Canker formation in
Southern California
walnut
Resistance to
Thousand Cankers
Disease may often
result from
differences in
susceptibility to
Geosmithia morbida

How did this happen?
- Somehow the beetle jumped hosts.

Walnut Twig Beetle Range
Expansion
“Big Bang” or
“Buttheads”

Spread of walnut twig
beetle through the
western states
involved human
transport of infested
wood products

States reporting presence of walnut twig beetle -2009

Native Distribution of Black Walnut,
Juglans nigra

What I said last spring…….
Good News: Walnut twig
beetle has likely not yet
reached the native range of
Juglans nigra (we think).

July 20, 2010 – Very, very bad news:
Thousand cankers and walnut twig beetles
found in the center of the native range of
Juglans nigra
Note: The local
foresters thought that
the trees were
suffering from
drought stresses
Knoxville, Tennessee

Thousand Cankers
has now breached the
geographic barrier of
the Great Plains!!!!

Implications of TCD Finding in
Native Range
• There are now no ecological or geographic
barriers that will prevent TCD spread
throughout the entire range of Juglans nigra
– Natural spread will be slow (comparably) but
inexorable
• Containment through restrictions on
movement of walnut wood products may
slow spread
• Aggressive management at edges of
infestation may slow spread

Slow the Spread of Thousand Cankers Disease!

Good News: Other Juglans species are
not as susceptible to TCD as is Juglans
nigra (black walnut). Pecan (Carya) are
apparently TCD resistant.

Good News: It takes a long
time (Decade? More? A bit
less?) for a tree to die
following initial colonization
by walnut twig beetles.

Bad News: By the time symptoms appear it can
be assumed that the walnut twig beetle is
generally distributed in the area.

Bad News: Prospects
for effective chemical
control of walnut twig
beetle are poor.

Drenching branch
sprays for walnut
twig beetle
Treatments have failed
to slow progress of
thousand cankers in
trees showing
symptoms

Systemic insecticide soil drenches/
trunk injections?
The fungus grows ahead of the beetle.
Cankered areas may prevent movement of
insecticide to the beetle feeding site.

Thousand Cankers Management &
Pesticides
What kind of crop is
black walnut?

Pesticides Used on Black Walnut Must
be Consistent with Labels for Nut-
• Probably legal
– Imidacloprid
– Chlothianidin
bearing Crops
• Not apparently legal for use on black
walnut
– Dinotefuran
– Abamectin
– Enamectin benzoate

Bad News: Prospects
for effective control of
walnut twig beetle are
poor. Insecticides
may slightly slow, but
will not stop the
progress of TCD.

Bad News: Walnut wood
with bark intact is
extremely infectious.

Two logs, ca 5 1/2-in diameter, 18-in length

23,040 Beetles/2 logs
= 35+
Beetles/inch 2

Bad News: Long distance movement of walnut
wood killed by 1000 cankers disease will be a
huge issue due to the high value of the saw
logs.

What about chipping?

Walnut twig beetles
were able to complete
development in larger
pieces following
chipping

A walnut log in Denver waiting for Uncle Benny from
Chicago

Beetle infested black walnut from Boulder area with bark
attached as advertised on the internet

What Needs to Be Done
• Strong public education on the threat
of Thousand Cankers Disease to black
walnut in its native range
• Immediate restriction, aided by national
quarantine, of all Juglans material that
may spread walnut twig beetle into the
native range of black walnut.

Immediate Action Needed:
Institute quarantine of all Juglans
wood of where thousand cankers
is present
X

A Juglans Quarantine
• Would affect logs/wood with bark
intact
• Would not need affect
– Milled wood without bark
– Logs that have sufficiently dried so live
beetles cease production (3 years?)
– Kiln-dried wood (questions remain about
reinfestation potential)
– Nuts

States with Existing or Proposed
• Missouri
• Iowa
• Kansas
• Wisconsin?
TCD Quarantines
• Michigan
• Indiana
• Nebraska
• North
Carolina

Slow the Spread of Thousand Cankers Disease!

TCD Training Workshops – Many states are
now trained in TCD diagnosis

An Interim Web Site for TCD information
Department of Bioagricultural
Sciences and Pest Management
Colorado State University
Click on “Extension and Outreach”