The Role of Amrosi nd Brk Beetles in Sudden Ok Deth Brice A McPherson 1 Dvid L. Wood 1 Ndir Erilgin 1 Pvel Svihr 2 Andrew J. Storer 3 Richrd B. Stndiford 1 1 University of Cliforni Berkeley 2 University of Cliforni Coopertive Extension, Novto 3 Michign Technologicl University, Houghton
Beetle tunneling cn kill P. rmorum-infected cost live ok without evidence of decy fungi
The totl impct (infected + ded) of SOD on cost live oks in Mrin County incresed in every plot from 00 to 06. 100 90 80 70 60 00 06 50 40 30 10 0 Plot
00 Cost Live Ok 9% Asymptomtic Bleeding Ded 24% 03 Cost Live Ok Asymptomtic Bleeding Ded 24% 67% 18% 58% 06 Cost Live Ok Asymptomtic Bleeding Ded 31% 52% 17%
Cost live ok infection levels hve remined reltively stedy s mortlity hs incresed in Mrin County disese progression plots, 00 to 06. Infected trees re shown s percentges of living, nd ded s percentges of totl numers of trees. 35 30 25 15 Infected Ded 10 5 0 00 03 06 Yer (Mrch)
The cumultive incidence of new infections nd mortlity mong cost live oks in Mrin County hs incresed stedily since 01. 40 35 30 25 Newly Symptomtic Newly ded 15 10 5 0 01 02 03 04 05 06 Yer
Weiull regression nlysis found considerle differences in medin survivl of cost live oks in 4 different cohorts : Asymptomtic (1), Bleeding only (2), Bleeding with Beetles (3), nd Bleeding with Beetles nd Hypoxylon (4). Ctegory (disese sttus) 1 2 3 4 Survivl (yers ± SE) 29.5 (8.4) 7 (1.2) 2.6 (0.3) 2.9 (0.3)
Helth nlysis: For oth cost live oks nd tnoks, stem dimeter (dh) predicts durtion in n symptomtic condition: s dh increses, proility of infection increses. Dh in 00 (cm) 10 40 80 (ok) 70 (tnok) Cost live ok 18.7 15.9 11.4 5.8 Tnok 3.8 3.2 2.3 1.4 Weiull helth nlysis: Figs. nd re cost live ok in Chin Cmp nd MMWD, respectively; c is tnok. The green line defines the men for ech popultion.
Why re the roles of rk nd mrosi eetles of interest? Erly ttcks re only found within the mrgins of cnkers >95% of ded, infected trees were ttcked y eetles while live Beetle-ttcked live trees hve ccelerted rtes of structurl filure These eetles re not reported to ttck trees tht pper to e vigorous Beetle ttcks on infected trees pper to e significntly ssocited with decresed survivl
Experimentl design Cost live oks were inoculted with P. rmorum in July 02 Insecticide (0.2% Permethrin) ws pplied in August 02 nd Mrch & August 03 Sticky trps were plced on the insecticide-treted inoculted nd mock-inoculted (wounded) trees in Mrch 03 Insecticide No Insecticide Inoculted Wounded Control Inoculted Wounded Control 40 40
Inocultion study results 80% of inoculted trees developed leeding within 1 yer 97% of ll eetles were trpped on inoculted trees Insecticide delyed eetle ttcks for up to 2 months, ut did not prevent them Bleeding cnkers mesured 9 months fter inocultion rnged in size from 0.008 m 2 to 1.13 m 2 7 sprotrophic eetle species were trpped: Monrthrum scutellre, M. dentigerum, Xyleorus clifornicus, Xyleorinus sxeseni, Gnthotrichus pilosus,pseudopityophthorus puipennis (rk eetle) (ll Cucurlionide, Scolitine), Scoici declivis (Bostrichide)
Totl Numer of Brk, Amrosi & Powderpost Beetles Trpped t Bleeding & Non-Bleeding Trees Men N Beetles (+/- SE)/Trp 50 40 30 10 0 Bleeding Non-Bleeding April My June Octoer Novemer
Beetle ttcks on insecticide-treted trees were consistently lower thn on untreted trees. This hs not resulted in differentil mortlity (yet?). 25 No Permethrin Permethrin 15 10 5 0 9 10 11 12 15 Months post-inocultion
Numers of eetle ttcks on permethrin-free trees in April predicted long-term disese sttus 40 35 30 25 Bleeding + Beetles Bleeding + Beetles + Hypoxylon 15 Ded 10 5 0 17 29 41 Months post-inocultion
Cnker size in April predicted long-term disese stge 0.8 c Bleed only Bleed + Beetles Bleed + Beetles + Hypoxylon Ded 0.6 c c c 0.4 c 0.2 0 17 29 41 Months post-inocultion
Beetle trp ctch in April - efore ny of the permethrintreted trees hd een ttcked - predicted long-term disese stge 50 45 c 40 Asymptomtic Bleeding Only 35 30 c c Bleeding + Beetles Bleeding + Beetles + Hypoxylon Ded 25 15 10 5 0 17 29 41 Months post-inocultion
Some conclusions nd specultions This pthogen continues to infect new trees nd spred within heterogeneous environments Simple extrpoltion from the pst 5 yers points to significnt mortlity in the ner future, ssuming tht nothing chnges significntly 40 35 30 25 Newly Symptomtic Newly ded 15 10 5 0 01 02 03 04 05 06 Yer 10
Some conclusions nd specultions The term resistnce my e difficult to define in terms of tree response to this pthogen. An infected cost live ok my e le to limit the extent of cnker expnsion, ut eetle ttcks, followed y fungl growth, my shift the lnce. Chrcteristiclly sprotrophic eetles re plying new roles in these environments y selectively ttcking cnkers on infected, ut pprently vigorous trees.
Acknowledgements Funding provided y US Forest Service, Pcific Southwest Reserch Sttion University of Cliforni Exotic/Invsive Pests Progrm University of Cliforni ANR Field nd l workers hve included (ut re not limited to) Dn Strk Griel Ritok-Owens Andrew Nelson Nicole Plkovsky Kim Kiernn Access nd ssistnce provided y personnel from Chin Cmp Stte Prk nd Mrin Municipl Wter District