Anthony Hanson1 and Rob Venette2 1University of Minnesota (hans4022@umn.edu)

2USDA Forest Service Northern Research Station (rvenette@fs.fed.us)

Emerald Ash Borer in the Midwest Agrilus planipennis Fairmaire

(Coleoptera: Buprestidae)

First discovered in North America near Detroit, MI in 2002 (Poland and McCullough 2006).

Discovered in Minnesota in 2009. Northwestern edge of invasion front.

United States Ash Density

http://extension.entm.purdue.edu/eab/images/ashLocations_sm.jpg

Emerald Ash Borer Parasitoids

Spathius agrili Yang, (Hymenoptera: Braconidae) 3.4 to 4.3 mm.

Tetrastichus planipennisi Yang, (Hymenoptera: Eulophidae) 1.6 to 4.1 mm.

Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) 0.95 mm. • Approved for release in by APHIS-PPQ in 2007.

• Parasitoids introduced and successfully overwintered in Michigan and Maryland (Ulyshen et al. 2011, Bauer & Liu 2007).

• Extent of cold tolerance is unknown.

Why is cold tolerance important?

Objectives

Objective 1: Determine the cold tolerance of the emerald ash borer parasitoids based on lab assays.

Objective 2: Predict expected mortality in locations where parasitoid overwintering potential is unknown.

Methods: Parasitoid Rearing Rearing regiments at EAB Biological Control Facility, Brighton, MI:

Temperature: Warm 18h 26.5

C: 6h 22.5

C, Cool 18h 20

C: 6h 15

C Photoperiod: Long 18h L: 6h D. Short 6h L: 18h D

O. agrili:

1. Diapause condtions (warm temperature / short photoperiod).

T. planipennisi: 1. Summer conditions (warm / long). 2. Fall conditions (cool / short).

S. agrili: 1. Summer conditions (warm / long). 2. 1 generation diapause (cool / short). 3. 2 generation diapause (1st generation warm / short, 2nd generation cool /

short).

Methods: Cold Tolerance Measures Lower Lethal Temperature

(LLTemp): mortality after instantaneous exposure from -15 to -35

C.

Supercooling Point (SCP): Temperature at which intracellular fluid freezes.

Lower Lethal Time (LLTime): 3 to 84 days at 0 to -15

C.

Mortality measured as discoloration 3 days after exposure or failure of adult emergence.

Thermocouple syringes and polystyrene cubes.

0

0.5

1

-40 -35 -30 -25 -20 -15 -10

Mor

talit

y

SEM

Temperature

C

Warm/short

1 gen. diapause

2 gen. diapause

S. agrili LLTemp

0

0.5

1

-40 -30 -20 -10 0

Pro

port

ion

Free

zing

Temperature

C

2 gen. diapause

1 gen. diapause

Warm/short

S. agrili Supercooling Points

Kuiper test: Warm/long vs. 1 gen. dia.:<0.0001 Warm/long vs. 2 gen. dia.:<0.0001 1 gen. vs 2 gen.:0.0931

0

0.5

1

-40 -35 -30 -25 -20 -15 -10

Cum

mul

ativ

e Pr

opor

tion

Temperature

C

LLTemp Mortality

Supercooling Points

S. agrili Freeze Tolerance

T. planipennisi LLTemp

0

0.5

1

-40 -35 -30 -25 -20 -15 -10

Mor

talit

y(fa

ilure

of p

upat

ion)

SEM

Temperature

C

Warm/short

0

0.5

1

-35 -30 -25 -20 -15 -10

Pro

port

ion

Free

zing

Temperature

C

Cool/short

Warm/Long

Kuiper test: Warm/short vs. cool/short.:<0.0001

T. planipennisi Supercooling Points

0

0.5

1

-40 -35 -30 -25 -20 -15 -10

Cum

mul

ativ

e Pr

opor

tion

Temperature

C

LLTemp Mortality

Supercooling Point

T. planipennisi Freeze Tolerance

0

0.5

1

-35 -30 -25 -20

Pro

port

ion

Free

zing

Temperature

C

T. planiepennisi

S. agrili

O. agrili

Kuiper test: T. planipennisi vs. S. agrili: 0.003 T. planipennisi vs. O. agrili: <0.001 S. agrili vs. O. agrili: <0.001

Cold-acclimated Supercooling Points

Climate Modeling

Model Choices:

• S. agrili cool/short 1st gen. diapause rearing LLTemp.

• T. planipennisi warm/long rearing LLTemp.

• Minimum annual air temperature data for 2002-2009 from weather stations (Midwest Regional Climate Center).

• Air temperature +1

C to account for under bark temps (Vermunt et al. 2012).

Predicted Mean S. agrili Cold Mortality 2002-2009

Predicted Mean T. planipennisi Cold Mortality 2002-2009

Lower Lethal Time

0

0.2

0.4

0.6

0.8

1

0 20 40 60 80 100Days of Exposure

LLTime: S. agrili Normal Rearing

0 -5

-10 -15

Temperature (°C)

Cum

m. P

erce

nt M

orta

lity

±SE

M

Cold Tolerance Conclusions

S. agrili more cold tolerant than T. planipennisi S. agrili appears freeze intolerant and T.

planipennisi primarily chill intolerant. O. agrili has the lowest supercooling point.

Length of time at warmer temperatures (0 to -15

C) can also be a significant source of

mortality.

Adult emergence measures for S. agrili ongoing.

Climate Modeling Conclusions • High mortality (>50%) in northern MN and

WI.

• Previous parasitoid recoveries in areas of low mortality.

• LLTime needs to be incorporated to model mortality in areas with warmer temperatures.

• Future research needed on minimum population levels for needed establishment.

Acknowledgements Funding support from USDA-APHIS and Minnesota

Legislative-Citizen Commission on Minnesota Resources.

Minnesota Department of Agriculture.

USDA Biological Control Facility, Brighton, MI.

References Bauer, L.S., Liu, H.P., 2007. Oobius agrili (Hymentoptera: Encyrtidae), a

solitary egg parasitoid of emerald ash borer from China. Lelito, Jonathan. USDA-APHIS EAB Rearing Facility, Brighton MI. Poland, T., and D. McCullough. 2006. Emerald ash borer: Invasion of

the urban forest and the threat to North America’ ash resource. J. For. 104: 118- 124

Vermunt, B., Cuddinton K., Sobek-Swant, S. Crosthwaite, J. 2012. Cold temperature and emerald ash borer: Modelling the minimum under-bark temperature of ash trees in Canada. Ecological Modelling 235-236: 19-26.

Ulyshen MD, Duan JJ, Bauer LS, Gould J, Taylor P, Bean D, Holko C, Van Driesche R. 2011. Field-cage methodology for evaluating climatic suitability for introduced wood-borer parasitoids: Preliminary results from the emerald ash borer system. Journal of Insect Science 11:141 available online: insectscience.org/11.141