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Susceptibility f Selected Juniper Cultivars t Cedar-Apple Rust, Kabatina Tip Blight, Cercspra Needle Blight and Btrysphaeria Canker 1 Ned A. Tisserat 2 and Jhn C. Pair Department fplant Pathlgy, Thrckmrtn Hall Manhattan, KS 66506-5502 r----------------- Abstract -------------------, The susceptibility f 39 juniper (Juniperus L.) cultivars t cedar-apple rust (Gymnsprangiumjuniperi-virginianae Schwein.), Kabatina tip blight (Kabatinajuniperi R. Schneider & Arx), Cercspra needle blight (Cercspra sequiae Ellis & Everh. var.juniperi Ellis & Everh.), and Btrysphaeria canker (Btrysphaeria stevensii Shemaker) was studied in field plantings lcated in Wichita and Manhattan, KS. Cultivars f J. scpulrum Sarg. shwed variable susceptibility t cedar-apple rust and mst were mderately t highly susceptible t Kabatina tip blight and Cercspra needle blight. Many were als severely damaged by Btrysphaeria canker. Mst J. virginiana L. cultivars were susceptible t cedar-apple rust but were mre resistant t ther disease prblems than J. scpulrum. Cultivars f J. chinensis were highly resistant t all fur diseases bserved in the plantings. Cnidia f B. stevensii were primarily cllected in spre traps in late May and June, suggesting this is a majr perid fr fungal infectin. ndex wrds: Gymnsprangiumjuniperi-virginianae, Cercspra sequiae var.juniperi, Kabatinajuniperi, Btrysphaeria stevensii, diseases, resistance. Species used in this study: Chinese juniper (Juniperus chinensis L.); Rcky Muntain juniper (Juniperus scpulrum Sarg.); eastern redcedar (Juniperus virginiana L.). Significance t the Nursery ndustry This study prvides infrmatin n the resistance f 39 cultivars f eastern redcedar, Chinese juniper and Rcky Muntain juniper t cedar-apple rust, Kabatina tip blight, Cercspra needle blight and Btrysphaeria canker. Cultivars f Chinese juniper were resistant t all fur diseases. Mst eastern redcedar cultivars were susceptible t cedarapple rust but mderately t highly resistant t the ther diseases. n cntrast, mst Rcky Muntain juniper cultivars were mderately t highly susceptible t Kabatina and Cercspra blights and Btrysphaeria canker and prbably shuld nt be used in lw maintenance landscape plantings. Nursery managers shuld avid heavy pruning r shearing fjunipers susceptible t Btrysphaeria canker in late May r June (peak spre release perid) t reduce chances f infectin. ntrductin Junipers are a cmmn cmpnent f landscape plantings thrughut Nrth America because f their adaptatin t a wide variety f gegraphic and micrclimatic cnditins. Several diseases may adversely affect the appearance and health f these trees and shrubs. Cmmn diseases include cedar-apple rust (Gymnsprangium juniperi-virginianae Schwein.), Phmpsis tip blight (Phmpsis junipervra Hahn), Cercspra needle blight (Cercspra sequiae Ellis & Everh. var. juniperi Ellis & Everh.), Kabatina tip blight 'Received fr publicatin March 27.1997: in revised frm June 27. 1997. We thank Michael Sheltn and Mike Darall fr maintenance f plts and Tim Tdd fr help n statistical analysis. Cntributin N. 97-494-J frm the Kansas Agricultural Experiment Statin. 'Prfessr. 'Prfessr. Dept. f Hrticulture. Frestry and Recreatin Resurces, Hrti culture Research Statin. 1901 E 95th St S, Wichita, KS 67233. 160 (Kabatina juniperi R. Schneider & Arx) and mre recently, Btrysphaeria canker (Btrysphaeria stevensii Shemaker). Althugh sme f these diseases, such as Cercspra needle blight and Phmpsis tip blight, can be cntrlled with fungicides (7), they may be prblematic in lw maintenance landscape plantings. Selectin and use fjuniper cultivars with resistance t ne r mre diseases wuld be a mre desirable apprach t cntrl. Sme juniper species and cultivars with resistance t ne r mre diseases have been identified (2, 3, 4, 5, 6, 10), but ratings f many widely used cultivars have nt been determined. n this study, the resistance f J. chinensis, J. scpulrum and J. virginiana cultivars t cedar-apple rust, Kabatina tip blight, Cercspra needle blight, and Btrysphaeria canker was evaluated. nfectin perids fr Cercspra needle blight, Phmpsis tip blight, and cedar apple rust are knwn (7, 8) and have been used fr timing f fungicide applicatins and in develping ther cntrls. n cntrast, relatively little is knwn abut cnditins favring infectin by B. stevensii. Wunding is apparently necessary fr infectin (12), but perids f spre prductin and infectin have nt been determined. We studied seasnal spre release f B. stevensii frm diseased junipers t identify infectin perids. Materials and Methds n 1981 and 1982, ne-year-ld grafts and rted cuttings f 39 cultivars f Juniperus scpulrum, J. chinensis, and J. virginiana (Table 1) were btained frm whlesale nurseries. These cultivars are still widely used in landscape plantings. Plants were ptted in 7.6 liter (2 gal) plastic cntainers in a sil:sand medium (: by vl) and grwn fr 3 4 years befre utplanting. n 1985, 3-5 plants f each cultivar were planted at the Hrticulture Research Center in Wichita, KS, and at the Rcky Frd Experimental Field in Manhattan, KS. Trees were planted in 4-5 rws apprximately 52 m (170.5 ft) in length and 4-5 m (13.1-16.4 ft) apart at each lcatin. Tree spacing within rws was 2 m
Table 1. Disease ratings f varius]uniperus cultivars t cedar-apple rust, Kabatina tip blight, Cercspra needle blight and Btrysphaeria canker. Cedar- Kabatina Cercspra Btryapple tip needle sphaeria rust" blight blight canker Y J. chinensis Ames O.Oa O.Oa O.Oa nne Blue Pint O.Oa 3.0h O.Oa nne Clumnaris hetzii O.Oa O.Oa O.Oa nne Keteleeri O.Oa O.Oa O.Oa nne Maneyii O.Oa O.Oa O.Oa nne Muntbatten O.Oa O.Oa O.Oa nne Perfecta O.Oa O.Oa O.Oa nne Rbusta Green O.Oa O.Oa O.Oa nne Spartan 0.2a 1.7cde O.Oa nne Wintergreen O.Oa O.Oa O.Oa nne J. scpulrum Blue Haven 1.5cde 3.0h 3.5de ++ Clgreen 2.df 1.7cde 3.0de ++ Dewdrp 1.7defg 2.0def 2.3bcde + Gray Gleam 1.6cdefg 2.4efg 0.3ab nne McFarland 1.7defg.Obc 4.0e ++ Medra O.Oa 2.0def 1.5abc ++ Mffettii 2.0efg 2.7fgh 2.3bcde nne Mnglw O.Oa 2.8gh 2.0abcd ++ Pathfinder 1.2bcd 2.2ef 2.5cde nne Platinum 0.9abcd.Obc 2.3bcde nne Silver Glbe 1.1 bcd.3bcd 0.7abc nne Skyrcket 1.3bcd 3.7i 2.5cde ++ Sparkling Skyrcket 1.8defg 3.3hi 3.0de ++ Sutherland 4.6j 1.0bc 2.3bcde + Table Tp 0.7abc 1.7cde 2.0abcd nne Welchii 0.7abc 2.3efg 1.7abcd + Wichita Blue 0.7abc 3.2hi 3.5de ++ J. virginiana Admiral O.7abc z 1.3bcd O.Oa nne Blue Muntain O.Oa O.la 0.3ab nne Burkii 3.0.Obc O.Oa nne Canaertii 4.6i 0.8b O.Oa nne Emerald Sentinel 2.0defg 1.0bc 0.3ab nne Grey Owl O.Oa O.la O.Oa nne Henryii 2.6gh.Obc 0.3ab nne HilJii Dundee 3.3hi.2bc O.Oa nne Hillspire O.Oa.Obc 0.3ab nne Manhattan Blue 4.0i 1.2bc O.Oa nne Oxfrd 1.0bcd 1.0b O.Oa nne Wren 2.0efg 0.8b O.Oa nne 'Means nt fllwed by the same letter are significantly different (P =0.05) by a prtected. pairwise cmparisn f least square means. Means fr rust and Kabatina tip blight are based n ratings taken frm 1993-1995 at tw lcatins. Means fr Cercspra needle blight based n ratings in 1995 at bth lcatins. 'Natural infectin and develpment f Btrysphaeria canker. A rating f nne =canker develpment nt bserved, + =canker develpment bserved n branch f at least ne tree f the cultivar at either Manhattan r Wichita, ++ =multiple cankers r extensive branch dieback resulting frm infectin n ne r mre trees f the cultivar. 'Disease severity fr rust, Kabatina and Cercspra was rated n a 0-5 scale where 0 =n disease; ] =light infectin with 1-19% f the branches with symptms (tip dieback, rust galls r diseased needles); 2 =mderate infectin with 20-39% f branches with symptms; 3 =mderate t heavy infectin with 40-59% f branches with symptms; 4 = heavy infectin with 60 79% branches with symptms and 5 = severe infectin with >800/0 fbranches shwing symptms r tree exhibiting significant dieback r decline. (6.6 ft). ndividual juniper cultivars were randmly assigned psitins within each planting, but replicate trees f each cultivar were planted tgether within the rw (Le., nt randmly blcked). T increase the severity fcedar-apple rust, a single cedar-apple rust-susceptible flwering crabapple (Malus sp.) was planted near the center feachjuniper planting. After planting, junipers were fertilized with 112 kg N per ha. Junipers received little maintenance after establishment. Weeds in rws and arund the base f trees were cntrlled yearly with pre-emergence herbicides r by mwing. Junipers were nt pruned, irrigated r fertilized after the first year. Juniper cultivars were rated each year fllwing field establishment fr natural infectin by K. juniperi, C. sequiae var. juniperi, and G. juniperi-virginianae. Disease severity was rated n a 0-5 scale where 0 = n disease; 1= light infectin with 1-19% f the branches with symptms (tip dieback, rust galls r diseased needles); 2 = mderate infectin with 20-39% f branches with symptms; 3 = mderate t heavy infectin with 40-590/0 f branches with symptms; 4 = heavy infectin with 60-79% branches with symptms; and 5 = severe infectin with >80% f branches shwing symptms r tree exhibiting significant dieback r decline. Disease ratings were analyzed by a mixed analysis prcedure (9) in which lcatin (Wichita, Manhattan) was treated as a blck (replicate) and year (1993, 1994, 1995) was treated as a strip plt. Ratings f the 3-5 replicates f each cultivar at each lcatin were averaged prir t analysis because they were nt true replicates. Statistical separatin f disease severity ratings amng cultivars was determined by prtected, pairwise cmparisns f least square means (9). The develpment f cankers fllwing artificial inculatins with B. stevensii was studied at the Manhattan lcatin nly. On August 19,1987, a branch (5-15 mm diameter) n three trees f each cultivar was inculated by inserting an agar blck cntaining mycelium f the fungus int a small wund made by a scalpel in the manner described by Tisserat et. al. (12). Sterile agar was inserted int three additinal branches t serve as cntrls. Canker develpment was determined by peridically measuring the length f disclred bark at the inculatin site. The experiment was repeated in May 1989. Seasnal release f cnidia (spres) f B. stevensii was studied in 1987 and 1988 by placing a Kramer-Cllins spre trap (Manhattan KS) apprximately 1 m (3.28 ft) frm a diseased J. scpulrum tree lcated in a Manhattan, KS, windbreak. Briefly, the spres were cllected by drawing air thrugh a small rifice n a clsed cntainer attached t a vacuum pump. Spres in the air were impacted n the surface f duble-sided transparent tape (Sctch Brand, 3M Center, Bx 33053, St. Paul, MN) thinly cated with petrleum jelly. The tape was wrapped arund the surface f a drum attached t a clck mechanism that made ne revlutin each week. The spre cllectr was run cntinuusly frm early March thrugh mid-september in bth years. Each week the tape was remved frm the surface f the drum and cut int sectins equal t a 24-hr sampling perid. Tape sectins were munted n a micrscpe slide and all cnidia f B. stevensii were cunted in tw randltlly selected passes acrss the length f tape at 400x magnificatin. A relative spre cunt fr each week was determined by summing the number f spres recrded fr each 24-hr sectin f tape. 161
Results and Discussin Natural develpment f cedar-apple rust, Kabatina tip blight and Cercspra needle blight was light and incnsistent n junipers during the first six years f the study then increased as trees matured and filled gaps within rws. This created mre favrable micrclimatic cnditins fr fungal infectin. There was n significant year (1993-1995) x cultivar interactin fr Kabatina tip blight and cedar-apple rust. Ratings fr these diseases remained relatively cnsistent during the last three years f the study. There was a significant year x cultivar interactin fr Cercspra needle blight because several J. scpulrum cultivars did nt develp symptms until 1995. n rder t reflect the ptential fr damage during envirnmental and/r cultural cnditins ptimal fr disease develpment, nly disease ratings frm 1995 are presented fr Cercspra needle blight. Juniper species and cultivars exhibited differences in susceptibility t cedar-apple rust, Kabatina tip blight and Cercspra needle blight (Table 1). All J. chinensis cultivars were highly resistant t all three diseases at bth lcatins. Mst cultivars f J. virginiana were very susceptible t cedar-apple rust althugh 'Admiral', 'Blue Muntain', 'Hillspire' and 'Oxfrd' shwed little r n rust develpment during the study. Kabatina tip blight and Cercspra tip blight develpment was lw r absent n all J. virginiana cultivars. n cntrast, mst cultivars f J. scpulrum had unacceptable levels (ratings >2.0) f bth Cercspra and Kabatina blights. Many als had lw t mderate susceptibility t cedar-apple rust. Cedar-quince [G. clavipes (Cke & Peck) Cke & Peck in Peck] and cedar-hawthrn [J. glbsum (Far!.) Far!.] rusts were nt fund n any cultivars during the study. This was prbably the result f a lack f inculum frm alternate hsts in the vicinity f the plantings. Further studies are needed t clarify whether there is a crrelatin in resistance ratings amng varius rust diseases n junipers. Kabatina tip blight was respnsible fr all f the branch tip dieback in bth plantings. nterestingly, Phmpsis tip blight was nt detected n any trees during the study. Phmpsis tip blight is ften a serius prblem f junipers during nursery prductin (2, 7) and is generally assumed t be the primary cause f branch tip dieback f J. hrizntalis (10). t is ften errneusly blamed fr branch tip dieback ccurring n ther juniper species. Symptms f Phmpsis tip blight and Kabatina tip blight are similar in that bth cause dieback f the terminal 2.5-7.6 cm (4-6 in) f sht grwth. Hwever, K. juniperi infects shts in fall (6) and results in sht death in early spring, whereas P. junipervra infects succulent sht grwth thrughut the summer mnths. Our results suggest that Kabatina tip blight is a mre cmmn cause f juniper sht dieback f 1. scpulrum and J. virginiana, at least in the Great Plains regin. All cultivars f J. chinensis, J. scpulrum, and J. virginiana inculated in 1987 and 1989 with B. stevensii develped sunken, resinus cankers within 6 mnths. Cankers tended t increase in length mre rapidly n J. scpulrum cultivars (data nt shwn), but quantitative assessment was difficult because many cankers rapidly girdled small diameter twigs. Furthermre, cankers did nt prgress frm small twigs int larger branches [> 3 cm dia (1.2 in)] r int the main trunk n any f the inculated trees. There was n natural canker develpment n J. chinensis r J. 162 virginiana cultivars at either site. Cnversely, many 1. scpulrum cultivars in bth Manhattan and Wichita plantings develped naturally ccurring, girdling trunk and branch cankers (Table 1) and suffered significant branch dieback. These results are cnsistent with ur bservatins and previus reprts (12) that Btrysphaeria canker is a destructive disease f J. scpulrum and is a limiting factr in the use f this species in Kansas windbreaks and landscape plantings. Branch cankers have ccasinally been bserved n 1. sabina L. and J. virginiana in landscape plantings in Kansas. Hwever, these species appear t be less susceptible than J. scpulrum. Btrysphaeria canker has been reprted in wa (1) and Pennsylvania (11) and is prbably distributed thrughut the United States. Cnidia f B. stevensii were cllected frm late May thrugh September in 1987 and frm mid-may thrugh July in 1988 (Fig. 1). A majrity f cnidia were depsited during a 6-wk perid in May and June. Spre depsitin usually ccurred n days with rain in excess f 0.3 cm (0.1 in) (data nt shwn). The abundance f cnidia, frequent rains, and temperatures favrable fr fungal infectin (12) suggest that new infectins ccur in May and June. Since B. stevensii 120 100 80 60 40 20 1200 1000 - Apr May Jun Jul 0 800 f/) '0 600 F 400 z Fig.. 200 Apr i. 1987 Aug 1988 May Jun Jul Aug Seasnal liberatin fbtrysphaeri stevensii cnidia. Each bar represents the relative number fspres cllected during a ne week sampling perid.
apparently requires wunding fr infectin (12), d nt prune r shear susceptible junipers during this perid. Literature Cited. Flynn, P. and Gleasn M. 1993. slatin fbtrysphaeria stevensii, cause f Btrysphaeria canker. frm Rcky Muntain juniper in wa. Plant Dis. 77:210 2. Hahn, G.G. 1940. Distributin and hsts fcedar blight in the United States. Plant Dis. Rep. 24:52-57. 3. Hanman. J.R.,J. Dney, M. Jhnsn. W. Funtain, and R. McNiel. 1994. Evaluatin f juniper cultivars fr susceptibility t Phmpsis and Kabatina blights, 1993. Bii and Cult. Tests furcnt. Plant Dis. 9: 161. 4. Hartman, J.R., J. Dney. M. Jhnsn. W. Funtain, and R. McNiel. 1995. Evaluatin fjuniper cultivars fr susceptibility t Kabatina tip blight, 1994. Bii and Cult. Tests frcnt. Plant Dis. 10:68. 5. Himelick. E.B. and D. Neely. 1960. Juniper hsts f cedar-apple rust andcedar-hawthm rust. Plant Dis. Rep. 44: 109-112. 6. Perry, R.G. and LJ. Petersn. 1982. Susceptibility and respnse f juniper species t Kabatina juniperi infectin in New Jersey. Plant Dis. 66:1189-1191. 7. Petersn, G.w. 1981. Pine and juniper disease in the Great Plains. USDA Fr. Ser. Gen. Tech. Rept. RM-86, 47 p. 8. Riffle, 1.W. and G.W. Petersn. 1986. Diseases f trees in the Great Plains. USDA Fr. Ser. Gen. Tech. Rept. RM-129, 149 p. 9. SAS nstitute. 1988. The ANOYA prcedure. Pages 125-154 in: SAS/ STAT User's Guide. Release 6.03 ed. SAS nstitute. Cary, NC. 10. Scheneweiss, D.E. 1969. Susceptibility f evergreen hsts t the juniper blight fungus, Phmpsisjunipervra, under epidemic cnditins. 1. Am. Sc. Hun. Sci. 94:609-611.. Stansz, G.R. and G.W. Mrman. 1997. Branch dieback fsavinjuniper in Pennsylvania caused by Dipldia mutila. Plant Dis. 81:. 12. Tisserat, N.A., A.Y. Rssman, and A. Nus. 1988. A canker disease f Rcky Muntain juniper caused by Btrysphaeria stevensii. Plant Dis. 72:699-701. 1. Envirn. Hrt. 15(3):160-163. September 1997 163