Cold-tolerance of Emerald Ash Borer Parasitoids
Cold-tolerance of Emerald Ash Borer Parasitoids
Cold-tolerance of Emerald Ash Borer Parasitoids
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<strong>Emerald</strong> <strong>Ash</strong> <strong>Borer</strong> <strong>Parasitoids</strong>Spathius agrili Yang,(Hymenoptera:Braconidae) 3.4 to 4.3mm.Tetrastichus planipennisiYang, (Hymenoptera:Eulophidae) 1.6 to 4.1mm.Oobius agrili Zhangand Huang(Hymenoptera:Encyrtidae) 0.95 mm.• Approved for release in by APHIS-PPQ in 2007.• <strong>Parasitoids</strong> introduced and successfully overwinteredin Michigan and Maryland (Ulyshen et al. 2011, Bauer& Liu 2007).• Extent <strong>of</strong> cold <strong>tolerance</strong> is unknown.
Why is cold <strong>tolerance</strong> important?
Objectives• Objective 1: Determine the cold <strong>tolerance</strong> <strong>of</strong> theemerald ash borer parasitoids based on labassays.• Objective 2: Predict expected mortality inlocations where parasitoid overwintering potentialis 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 DO. 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 (1 st generation warm / short, 2 nd generation cool /short).
S. agrili LLTemp1Warm/shortMortality SEM0.51 gen. diapause2 gen. diapause0-40 -35 -30 -25 -20 -15 -10Temperature C
1S. agrili Supercooling PointsProportion Freezing0.52 gen. diapause1 gen. diapauseWarm/shortKuiper test:Warm/long vs. 1 gen. dia.:
S. agrili Freeze Tolerance1Cummulative Proportion0.5LLTemp MortalitySupercooling Points0-40 -35 -30 -25 -20 -15 -10Temperature C
Mortality(failure <strong>of</strong> pupation) SEMT. planipennisi LLTemp1Warm/short0.50-40 -35 -30 -25 -20 -15 -10Temperature C
T. planipennisi Supercooling Points1Proportion Freezing0.5Cool/shortWarm/LongKuiper test:Warm/short vs. cool/short.:
T. planipennisi Freeze Tolerance1Cummulative Proportion0.5LLTemp MortalitySupercooling Point0-40 -35 -30 -25 -20 -15 -10Temperature C
<strong>Cold</strong>-acclimated Supercooling Points1Proportion Freezing0.5T. planiepennisiS. agriliO. agriliKuiper test:T. planipennisi vs. S. agrili: 0.003T. planipennisi vs. O. agrili:
Climate ModelingModel Choices:• S. agrili cool/short 1 st gen. diapause rearing LLTemp.• T. planipennisi warm/long rearing LLTemp.• Minimum annual air temperature data for 2002-2009from weather stations (Midwest Regional ClimateCenter).• Air temperature +1 C to account for under barktemps (Vermunt et al. 2012).
Predicted Mean S. agrili <strong>Cold</strong> Mortality 2002-2009
Predicted Mean T. planipennisi <strong>Cold</strong> Mortality 2002-2009
Lower Lethal TimeCumm. Percent Mortality ± SEM10.80.60.40.20LLTime: S. agrili Normal RearingTemperature (°C)0 -5-10 -150 20 40 60 80 100Days <strong>of</strong> Exposure
<strong>Cold</strong> 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 <strong>of</strong> time at warmer temperatures (0 to-15 C) can also be a significant source <strong>of</strong>mortality.• Adult emergence measures for S. agrili ongoing.
Climate Modeling Conclusions• High mortality (>50%) in northern MN andWI.• Previous parasitoid recoveries in areas <strong>of</strong>low mortality.• LLTime needs to be incorporated to modelmortality in areas with warmertemperatures.• Future research needed on minimumpopulation levels for needed establishment.
Acknowledgements• Funding support from USDA-APHIS and MinnesotaLegislative-Citizen Commission on MinnesotaResources.• Minnesota Department <strong>of</strong> Agriculture.• USDA Biological Control Facility, Brighton, MI.
References• Bauer, L.S., Liu, H.P., 2007. Oobius agrili (Hymentoptera: Encyrtidae), asolitary egg parasitoid <strong>of</strong> emerald ash borer from China.• Lelito, Jonathan. USDA-APHIS EAB Rearing Facility, Brighton MI.• Poland, T., and D. McCullough. 2006. <strong>Emerald</strong> ash borer: Invasion <strong>of</strong>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.<strong>Cold</strong> temperature and emerald ash borer: Modelling the minimum underbarktemperature <strong>of</strong> ash trees in Canada. Ecological Modelling 235-236:19-26.• Ulyshen MD, Duan JJ, Bauer LS, Gould J, Taylor P, Bean D, HolkoC, Van Driesche R. 2011. Field-cage methodology for evaluatingclimatic suitability for introduced wood-borer parasitoids: Preliminaryresults from the emerald ash borer system. Journal <strong>of</strong> Insect Science11:141 available online: insectscience.org/11.141
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