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What is an EAB’s Favorite Meal and Why is it Important?. Therese M. Poland Deborah G. McCullough Andrea C. Anulewicz Deepa S. Pureswaran. EAB Host Range. China - Fraxinus spp. Japan & Korea – Juglans - Pterocarya - Ulmus North America - ??. Why Study Host Range?.
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What is an EAB’s Favorite Meal and Why is it Important? Therese M. Poland Deborah G. McCullough Andrea C. Anulewicz Deepa S. Pureswaran
EAB Host Range China - Fraxinus spp. Japan & Korea – Juglans - Pterocarya- Ulmus North America - ??
Why Study Host Range? • Know what species are at risk • Understand susceptibility of urban & forest trees • Improve survey and detection • Enhance management options • Propogate and enhance resistance
Host Range Objectives Assess EAB feeding preference & larval development (1) Alternate species of concern (2) Compare North American Species (3) Stressed & vigorous trees (4) North American & Asian ash
(1) Alternate Species of Concern No-choice lab bioassay Caged adult female & male with wood section & ash leaf. American elm, black walnut, shagbark hickory, hackberry & privet tested. Reared until females died. After 4 weeks, eggs counted & bark dissected to assess 1st stage larval galleries.
Mean no. eggs per cm2 no-choice test; n = 5 No. eggs per cm2
No-choice lab bioassay Black walnut Black ash
Caged-Stem Bioassay Screen cages confined 3 pairs of beetles on each tree Dead beetles replaced June-Sept. Stems dissected: 4 blocks in Nov.6 blocks in March Repeated in 2004 & 2005
Host Range Field Tests Ash, Elm, Walnut, Hickory, Hackberry logs & drain pipe set on t-posts at 4 sites. Adult landing rates monitored using Tanglefoot. Logs dissected.
Landing Rates of EAB Adults Total adults Elm Hickory Green ash Pipe White ash Hackberry Black walnut
Host Range Field Tests Green ash, elm & walnut logs suspended in heavily infested ash tree canopies; Will EAB females make a mistake? Logs dissected.
Mean density of EAB galleries per m2in Suspended logs 3 logs per tree on 5 trees in 2 sites; 30 total logs Green ash 195.5 ± 49.5 Elm 0.0 Walnut 0 ± 0
Host range field test: 1st & 2nd stage larvae inserted into green ash, elm & black walnut
Larval insertion: green ash, elm & black walnut trees & logs
Alternate Species Results • Adults will oviposit on alternate species under no-choice conditions. • Oviposition “mistakes” occur but rare. • 1st stage larvae fed readily on ash species; a few larvae attempted to feed on other species but development impaired.
(2) Preference Among North American Ash Species Green vs. White ash trees 4 neighborhoods over 3 years. 2003: canopy dieback was significantly higher in green ash than white ash 2004: canopy dieback increased in both species, still higher in green ash 2005: canopy dieback reached 100% for most green ash and rose sharply in white ash Similar pattern for exit holes and woodpecker attacks.
Preference Among North American Ash Species White vs. Blue ash trees 2 woodlots over 2 years. 2004: exit holes and woodpecker attacks were significantly higher in white ash than blue ash 2005: exit holes and woodpecker attacks increased in white ash but not blue ash and the difference was more significant.
Host selection and feeding preference on ash spp. • Green – F. pennsylvanica • Black – F. nigra • White – F. americana • Blue – F. quadrangulata • European – F. excelsior • Manchurian – F. mandshurica
Experimental set up beetles released
Host selection - landing • number of beetles on each ash species counted every 2h during the day for 48h • Feeding preference – amount consumed • Leaves were scanned before and after the experiment • Amount fed determined
a 2 males 1.8 Host selection - landing b 1.6 b 1.4 No. of beetles on foliage (mean +SE) 1.2 c 1 c 0.8 c 0.6 0.4 0.2 0 a 2.2 females 2 ab ab 1.8 1.6 1.4 bc 1.2 c c 1 0.8 0.6 0.4 0.2 0 green black white blue European Manchurian species
ab a males 12 Feeding preference 10 8 ab bc 6 4 cd d 2 0 Amount of foliage consumed (%) 14 a females a 12 a a 10 8 b 6 b 4 2 0 green black white blue European Manchurian species
(3) Stressed and Vigorous Trees Trap trees with different stress treatments: Girdled, herbicide, methyl jasmonate, wounded Plantation study:Girdled, fertilized, and control trees of different ash species
(4) Beetle performance on American vs. Asian Species • Raised beetles (n=40) on green and Manchurian ash until they died • Leaves changed and retrieved each week • Measured amount consumed, weight gained / lost over two weeks and longevity
Foliage consumption 16 a 20 a 14 18 12 16 14 10 b 12 total amount consumed (cm)2 proportion consumed (%) 8 10 b 8 6 6 4 4 2 2 0 0 green Manchurian green Manchurian
Beetle performance a a 6 20 a 18 a 5 16 14 4 longevity (days) 12 weight loss at age 2 weeks (mg) 3 10 8 2 6 4 1 2 0 0 green Manchurian green Manchurian
Results • Total amount and proportion of foliage consumed was greater in beetles fed on green ash compared to Manchurian • No difference in weight or longevity
What may be going on? • Higher nutritive value of Manchurian ash? • Presence of anti-feedants in Manchurian ash? • Higher consumption of green ash by larvae — mortality of trees in North America?
Compounds Identified and Quantified in Different Ash Species • hexanol • E-2-hexenal • Z-3-hexenol • E-2-hexenol • butoxyethanol • Z-3-hexenyl acetate • hexyl acetate • E-β-ocimene • nonanal / linalool • nonatriene • Z-E-α-farnasene Green White Black Blue European Manchurian
healthy 3 green 2.5 black white 2 blue 1.5 European Manchurian 1 0.5 0 -0.5 -1 -1.5 -3 -2 -1 0 1 2 3 4 stressed 2 1.5 1 0.5 0 -0.5 -1 -1.5 -2 -2.5 -3 -3 -2 -1 0 1 2 3 4
Hybrid study • North American ashes are preferred relative to Chinese ashes • What would happen with hybrids? • Crossed F. americana with F. chinensis to obtain two putative hybrids chiam1 and chiam2 • Tested beetle landing and feeding on the four genotypes • Compared volatile profiles by aeration
Host selection by landing and feeding preference F. americana F. chinensis Chiam 1 Chiam 2
Hybrid study: landing Mean number of beetles Observations over time
30 25 20 15 10 5 0 16 14 12 10 8 6 4 2 0 F. americana F. chinensis Chiam 1 Chiam 2 Hybrid study: feeding a a a a amount consumed (cm2) (mean + SE) a a a a proportion consumed (%) (mean + SE) species
Hybrid study: Aerations Super-Q
Compounds quantified • hexanal • e-2-hexenal • z-3-hexenol • e-2-hexenol • z-3-hexenyl acetate • hexyl acetate • e-β-ocimene • nonanal / linalool • farnesene Gas chromatography
Hybrid study: Comparison of volatiles F. americana 40 35 30 25 20 15 10 5 0 F. chinensis 40 35 30 25 20 15 10 5 0 chiam1 Amount(ng / g dry wt) 40 35 30 25 20 15 10 5 0 40 chiam2 35 30 25 20 15 10 5 0 e-ocimene hexanal nonanal farnesene linalool z-3-hexenol e-2-hexenal e-2-hexenol hexyl_acetate z-3-hexenyl_acetate
Hybrid study - Results • Landing and feeding: no significant differences • Hybrids have taken on some characteristics from F. americana parent • Volatile profiles of hybrids different from either parent – may not be simply inherited
Conclusions • EAB feed and develop in all ash species • No evidence of larval survival or development on any non-ash species • EAB prefer Green>Black>White>>Blue ash • EAB prefer N. American ash to Asian ash • Hybrids may be intermediate and volatile characteristics are not simply inherited • Surveys should focus on preferred trees (green ash) • More research needed to develop resistance and attractive lures