Tamarack Pests

Tamarack Pests
• Mostly found on wet to moist organic
soils, but also grows well on upland
mineral and loamy soils.
• Used for pulpwood & wildlife
• Large losses due to insects
Mike Albers
1

Tamarack
Pioneer species –only deciduous conifer in MN
very intolerant to shade
one of the fastest growing conifers
Approximately 1,000,000 acres of tamarack covertype in MN
Over 50% of tamarack is on state lands
Tamarack is under utilized
2007 estimates - sustainable harvest = 115,000 cords/yr
- actual harvest level 53,000 cords
Tamarack historically – public land survey-most abundant tree in MN
– now 6 th or 7th
Large losses due to I&D problems
I&D
larch sawfly
decays, root rots
blue stain fungi
larch casebearer
eastern larch beetle
2

Larch sawfly
Found around the world where larch grows.
Historically has caused continent wide outbreaks with high levels of mortality
Is it native or not? Coulson&Witter = 4 strains in NA - 2 strains native and 2 non-native.
One generation per year.
Larvae defoliates tamarack. Tree mortality after 7 or more years of defoliation.
3

History of Larch sawfly
outbreaks and parasites
Defoliation east of Grand Rapids 1997
Wide spread outbreaks and mortality in North America from 1880s - 1970’s
First record in MN in 1909. (tree ring analysis – defoliation events in 1840’s &1880’s)
MN outbreak 1910 -1926 = 1 billion board feet killed.
Parasite from Britain released in Manitoba in 1913. Spread through NA.
Fewer outbreaks and less mortality 1930’s and 1940’s
Larch sawfly became immune to this parasite by the late 1940’s.
MN outbreak late 1940s -1970’s reported that 40% of tamarack in MN killed.
1960s a Bavarian strain of the parasite plus another ichneumon released Manitoba.
In 1971 & 72 -released in northern MN. (UMN & DNR)
Since then short outbreaks with little mortality.
Last defoliation I saw in MN was ‘97. App 10 acres.
5

Stem decays
Ontario 1950’s
Phellinus pini – red ring rot, red heart
white pocket decay
Fomitopsis officinalis
brown trunk rot
6

Root and butt rots
Armillaria root rot
Tomentosus root rot
red butt rot
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Fungi Isolated from Eastern Larch Beetles in
Minnesota
Ophiostoma floccosum
Ophiostoma picea
Ophiostoma ips
Leptographium abietinum
Pesotum fragrans
Phlebiopsis gigantea
Pichia scolyti
* based on DNA sequencing
Work by Andy Graves -UC Davis, Robert Blanchette-U of MN, Tom Harrington-
Iowa State
Blue stain fungi – degrade wood quality, may help kill trees by plugging vessels,
may be food source for beetles 8

Larch casebearer
Exotic needle miner- first found in NA in 1886, Lake States 1920’s - larvae eat the inside of the
needle - persistent defoliation by 1930’s led to release of parasites from Europe.
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Outbreak since 2000
Likely cause stress
but have seen no mortality
to date
Larch casebearer
30000
25000
20000
Acres
15000
10000
5000
0
2005 2006 2007 2008 2009 2010 2011
11,400 ac
in 2011
10

Eastern larch beetle
Dendroctonus simplex
• Native to North America
• Large range throughout Canada
and the United States
• Colonizes eastern larch
(tamarack), Larix laricina
• ‘Secondary’ bark beetle?
(Bark Beetles of Canada and Alaska 1976 – says
ELB is not of economic importance.)
Seybold et al. 2002
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Larch beetle mortality 2000 through 2011
Mortality on 123,000 acres
Tamarack covertype = 1,000,000 acres
Mortality = 12% of covertype
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August 2011
13

August 2011
14

Acres
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
New acres of tamarack mortality caused
by larch beetle, 2000 to 2011
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
140000
120000
100000
Cumulative acres of tamarack mortality
caused by larch beetle, 2000 to 2011.
Acres
80000
60000
40000
20000
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
15

Tamarack mortality due to Eastern larch Beetle 2011
29,000 acres
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Life-cycle
Callow adult
Brood adult / Mature adult
Eggs
Pupa
Larva (4 instars)
17

Reproductive biology
Brood
1
Summer re-emergence
late June – mid July
Brood
2
mid May – late June
mid July – mid Aug.
Spring emergence
early May – mid June
late June – early Aug.
late July – late Oct.
mid July – mid Aug.
mid Aug. – early Oct.
late Aug – next May
Immature
early Oct. – Dec
Immature
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Langor 1987a, b

Heavy resin flow
from attacked
trees
Small entrance holes
In July some trees start to show yellowing and browning of needles often on lower part of tree.
50% of trees being attacked show no color change during growing season but are dead next spring. Makes aerial
detection of current year activity difficult.
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Black backed woodpecker 20

Why is Eastern Larch Beetle causing so much tamarack
mortality?
Warmer winters and longer growing seasons?
Precipitation levels? Drought, high water levels
Stand conditions? Age, stand composition, vigor
Changes in larch beetle behavior? Secondary, primary
Is larch casebearer stressing tamaracks making them susceptible to LB?
21

What is causing the eastern larch beetle outbreak in MN?
Is larch casebearer defoliation predisposing tamarack to attack by larch beetle?
Larch Beetle
2000-2009
Larch Casebearer
2000 - 2009
92,000
acres
mortalti
y from
larch
beetle
92,000 acres
mortality by
larch beetle
47,500 acres
defoliated by
larch
casebearer
By 2000-2009 0nly 4152 acres have had both larch beetle and larch casebearer
= 4.4% of larch beetle mortality
22

Stand conditions
Age and DBH – seems to prefer larger DBH but attacks and kills down to 2”
- seems to attack older larger trees first but found on 40 year old trees
and up
Upland vs lowland- kills trees on upland and lowland sites
Mixed species stands vs pure tamarack stands- ELB doesn’t seem to care
a tamarack is a tamarack
These questions need more research
23

What is causing the eastern larch beetle outbreak in MN?
Is drought or high water predisposing tamarack to attack by LB?
Tamarack mortality
became apparent
starting in 2000.
Upland vs lowland
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Longer growing season – more demand on soil moisture ,
longer growing season for LB to mature
4+ wks
25

Overwintering of ELB
Confusion in the literature
Wood, 1982 – Principal overwintering stage is the adult, also find some larvae.
Werner, 1986- Overwinters as adults beneath bark
Langor & Raske, 1986 – Only adults overwinter. Cold temps kill larvae &
pupae.
In Minnesota based on collections
from above the snow line, made in
late winter of 2002 – 2009 adults and
larvae survive.
Are warmer winters allowing more LB to
overwinter resulting in increased tamarack
mortality? 26

Procedure for measuring
supercooling points of bark beetles
LB are freeze intolerant
have to super cool when
temps are below freezing.
Dr Rob Venette
NRS, St Paul, MN
Abby Walter
U of MN
-80.0°C
27

Seasonal changes in mean supercooling point (±SEM) of
larval and adult Dendroctonus simplex.
ELB are freeze intolerant
-16C
(+3.2F)
-17.5 (+1.4F)
-43F
-49C (-56F)
-56F
Rob Venette
NRS, MN
-42C (-43F)
Abby Walter
U of MN
28

Predicted impacts of winter low temperatures on Eastern larch
beetle populations
Larvae are extremely
cold-tolerant –most
survive winters.
Low winter
temperatures
increased 0.25C /yr
1964-2004.
Adult survival has
increased 0.7% /yr
from 1964-2004.
Greater overwintering
success by ELB and
may lead to increased
tree mortality
Minimum annual temperature (°C)
-24
-26
-28
-30
-32
-34
-36
-38
-40
-42
-44
-46
0.0
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Winter temperatures for Isle, MN
Year
Larval survival
Adult survival
just south of Mille Lacs Lake
1.0 100%
0.8 80%
0.6 60%
0.4 40%
0.2 20%
From -Proceedings Society of American foresters, 2008, Reno, Nevada
In Press- Forrest Health Monitoring 2008, National Report 29
8
0
%
Proportionate survival (predicted)

Currently…….
I still do not know what factor or factors might be involved in the
eastern larch beetle outbreak in Minnesota .
It appears possible that warmer winter temperatures and maybe
longer growing season may be a factor.
And, help from the U of MN is on the way.
30

Current Research on ELB in MN
• Fraser McKee, PhD student
• Advisor -Dr. Brian Aukema U of MN Dept of Entomology
• First field work completed last summer. Just received
funding for 3 more years. Research will be mostly near
Baudette.
Committee members
• Drs. Tony D’Amato, Steve Kells, Rob Venette
MN Department of Natural Resources
• Val Cervenka, Jana Albers, Mike Albers, Becky Lein,
Gretchen Mehmel, Mike Hoppus
31

Research Background
Only two major studies on the
biology of the eastern larch beetle
• Alaska (Werner 1986)
• Newfoundland, Canada (Langor &
Raske 1987a,b, 1988)
No comprehensive case-study for
the Midwest region
Field observations of insect biology
in MN differ markedly from the
published literature
Seybold et al. 2002
?
32

Research
Studies of insect biology
• Understand the contribution of each larval brood to the
reproductive population of beetles
• More accurately define the over-wintering biology and
ability of the beetles to engage in host attack and
reproduction earlier in the year
33

Research
Studies of insect biology
• Understand the contribution of each larval brood to the
reproductive population of beetles
• More accurately define the over-wintering biology and
ability of the beetles to engage in host attack and
reproduction earlier in the year
Landscape-level analysis of the outbreak
• Identify the climatic variables potentially driving the current
outbreak
34

Research
Studies of insect biology
• Understand the contribution of each larval brood to the
reproductive population of beetles
• More accurately define the over-wintering behavior and
ability of the beetles to engage in host attack and
reproduction earlier in the year
Landscape-level analysis of the outbreak
• Identify the climatic variables potentially driving the current
outbreak
Stand-level analysis of tamarack growth rates and
beetle host selection
• Determine if a widespread decline in tamarack growth is
occurring in Minnesota
• Provide information on how beetles are interacting with the
tamaracks present on the current landscape
35

Research
The influence of tamarack quality on host
selection and subsequent reproductive
success
• Provide information on beetle-host interactions at a
fine scale
• Examine how the health of individual tamaracks
contributes to the reproductive success and
population dynamics of the beetle
36

Questions
37