Diseases of Echinacea on the Canadian Prairies

Transcription

1 April 1999 Agdex Introduction Diseses of Echince on the Cndin Priries Crop production trends on the Cndin Priries during the pst decde hve moved towrd diversifiction nd the incresed production of exotic her, spice, essentil oil nd medicinl plnts. Alert nd Ssktchewn re considered to e mong the most desirle res in the world to cultivte romtic nd medicinl hers. Fctors such s the pristine environment, the vilility of high qulity griculturl lnd nd the rigourous climte ll serve to increse the mount nd qulity of ctive ingredients produced in mny medicinl hers. Echince Echince (Echince spp.) hs recently ecome one of the most common nd highly vlued medicinl plnts on the Cndin Priries (Figure 1). The cultivted crege of echince is incresing stedily ecuse of the high vlue nd strong demnd for this crop worldwide. There re severl commercil plntings throughout Alert nd Ssktchewn. Echince is primrily hrvested for its roots, three to four yers fter plnting. Root products re used to strengthen the humn immune system nd hve gined populrity in the helth nd phrmceuticl food mrkets. Three species of echince re currently grown in Cnd. Nrrow-leved purple coneflower (Echince ngustifoli DC.) is the most populr ecuse it contins more concentrted ctive ingredients thn the other two species. Purple coneflower (E. purpure (L.) Moench.) is more populrly grown s n ornmentl flower. Ple purple coneflower (E. pllid Nutt.) is not s widely grown. Millions of echince plnts hve een grown under greenhouse nd field conditions in the Pririe provinces. Figure 1. Echince is ecoming populr. Diseses Along with new crops cn come diseses tht hve rrely, if ever, een seen on the Priries. Severl new diseses hve een found in echince plntings in the pst few yers, ut mny growers re not yet fmilir with their symptoms. These diseses, if not properly controlled, cn cuse serious losses in echince crops. Erly detection could help prevent the spred of these diseses nd reduce the dmge to stnding crops. This fctsheet will help growers ecome fmilir with disese symptoms nd recommendtions for their control. Bsed on survey results conducted in Alert in 1997 nd 1998, six mjor diseses of echince were identified: ster yellows sclerotini stem rot dmping-off fusrium crown nd root rot otrytis light lternri lef spot 1

2 Since mny producers of medicinl hers prefer to grow their crops under orgnic production systems, the use of iologicl nd culturl pest control mesures should e explored long with trditionl pesticides. Aster yellows Aster yellows, cused y the ster yellows phytoplsm, ws first seen on E. purpure nd E. ngustifoli t Brooks in 1994 nd All three species of Echince re susceptile to ster yellows. However, E. ngustifoli hs shown lower incidence of this disese thn E. purpure in field plots. The right yellowing of leves cused y phytoplsm infection is especilly pprent in the erly spring when young shoots emerge from the ground (Figure 2). Figure 3. Phytoplsm infection cuses prolifertion of xillry shoots. Infected plnts (left) hve unchy, or witch s room, ppernce. Helthy plnt is on the right. In mid-summer, when echince typiclly reches its flowering stge, florl mlformtions involving virescence (greening) nd phyllody (conversion of florl prts to leves) re prominent (Figures 4 to 6). Smll, secondry, sterile florets issue from the originl flower heds. Figure 2. Phytoplsm infection in young plnt of E. ngustifoli (right). Note yellowing of leves. As the disese progresses, symptoms of lef reddening, plnt stunting nd prolifertion of xillry shoots pper (Figure 3). Figure 4. Phytoplsm infection in E. purpure. Note greening nd distortion in disks nd ry florets. 2

3 Trnsmission electron nd fluorescent microscopic techniques cn e used to look for phytoplsm prticles in the phloem tissues. A lrge numer of phytoplsm odies re usully present in the sieve tue cells of ffected leves nd phylloid flower pedicels (Figure 7). Most of the phytoplsm odies re sphericl to ovoid or irregulr in shpe, surrounded y single memrnes nd lck cell wlls. Figure 5. Close-up of n infected flower of E. purpure with symptoms of virescence (greening) nd prolifertion of disk florets. Figure 7. Electron microgrph of phytoplsm odies (circulr to ovl ojects) ccumulted on one side of sieve plte of phloem cell. Figure 6. Pytoplsm infection cuses distortion nd virescence (greening) of ry nd disk florets (left). Norml flower ppers on the right. Disesed plnts re suject to winter kill nd infections cused y soil-orne pthogens. Symptoms ecome noticele y erly June nd usully occur on two- or three-yer-old plnts. Since flower prts re chnged into vegettive leves nd sterile florets in the infected plnts, no seeds re produced. Therefore, the disese hs tremendous impct on echince seed production. Control of ster yellows The pthogen is trnsmitted etween plnts primrily y lefhoppers nd y the dividing of roots/crowns of infected plnts. Control mesures cn e tken s follows: control nd mow down perennil weeds tht my hrour phytoplsms pply low-toxicity insecticides such s mlthion or pyrethrin onto surrounding weeds to control lefhoppers grow echince plnts with repellent crops such s yrrow, grlic nd mint select helthy plnts for vegettive propgtion when dividing crowns nd roots pull out nd destroy plnts tht show typicl symptoms of phytoplsm infection Sclerotini stem nd root rot The fungus Sclerotini sclerotiorum cn infect stems nd form drk rown to lck lesions t nd ove the soil level. Ded leves often hve leched petioles. Infected stems nd petioles my disintegrte, leving only firous tissues intct. Roots ecome rotted nd lck. 3

4 This pthogen genertes lrge mounts of white myceli under moist soil conditions, nd lck, olong to irregulr-shped scleroti (Figure 8) form on the root surfce nd crown res fter plnt deth. When infection occurs in the upper stems nd shoots, it origintes from eril scospores nd cuses stem lotches nd dieck (Figures 9 to 11). Disesed plnts re esily pulled from the soil. The pthogen needs moist conditions to estlish nd intensify the disese. The disese cn ecome very destructive when such conditions exist. Figure 10. Sclerotini light cuses rpid wilting of dult plnts ccompnied y drooping of flower heds. Figure 10. Advnced symptoms of sclerotini light cuse the whole plnt to collpse. Figure 8. Wilting of young shoot of E. purpure indicting infection with Sclerotini sclerotiorum. Figure 8. Sclerotini light cuses fryed ppernce where the stem reks. Irregulrly-shped drk odies (scleroti) re often found inside the stem fter the disese hs killed the plnt. Figure 11. Florl infection nd dieck of upper stem of E. ngustifoli cused y eril spores of Sclerotini sclerotiorum. Figure 11. Folir nd stem infection of E. purpure cused y eril spores of Sclerotini sclerotiorum. Figure 9. Sclerotini light cn cuse rpid deth in young echince plnts when it ttcks crowns. Leves ecome rown, dry nd rittle. 4

5 Control mesures 1. Crop rottion Sclerotini hs very rod host rnge nd cn infect mny different species of crops. It often requires more thn three yer rottion with cerels, grsses or corn crops to reduce the pthogen popultion in the soil. Therefore, echince should not follow cnol, sunflower, ens or other susceptile crops. 2. Resistnt cultivrs E. purpure is usully more resistnt to the pthogen thn E. ngustifoli. 3. Chemicl control No fungicides re currently registered in Cnd for controlling this disese. Seedling Dmping-off Figure 13. Pythium root rot. Echince seedlings showing withered leves. This disese is cused y vrious fungi, e.g. Pythium spp., Rhizoctoni solni, Fusrium spp. nd Alternri spp. Long periods of strtifiction my predispose seeds to pre-emergence dmping-off (Figure 12). Figure 14. Dmping-off cused y Rhizoctoni cn spred quickly through unsterilized soil. One-month old seedlings infected with Rhizoctoni solni. Cotyledons nd first lef hve lost their turgidity nd strted to wilt. Figure 12. White Pythium mycelium ppers on ffected seeds fter four weeks strtifiction t 4 C. Infection spreds from infected seeds to helthy seedlings. The pthogens occur in contminted growing medi nd cuse significnt losses under cool, dmp conditions, which often previl in greenhouses during the spring (Figures 13 nd 14). Disesed plnts first show lckening of the root tips, followed y rowning of the root nd stem, shrinking of the cotyledons nd twisting of young leves (Figure 15). Finlly, seedlings wilt nd collpse onto djcent plnts. Under conditions fvourle for disese development, seedlings my suddenly collpse due to tissue disintegrtion t the roots nd stem. The disese spreds through contct with infested medi, roots or plnt mterils. Figure 15. Rhizoctoni root rot. Lower stem ppers discolored. Affected stems my hve smller dimeter thn helthy sections, giving the stem pinched ppernce. Cotyledons my senesce premturely. 5

6 Control mesures 1. Culturl prctices Use pthogen-free growing medi nd do not overwter seedlings. 2. Chemicl control No seed tretments re currently registered for use on echince in Cnd. Botrytis light This disese is cused y the fungus Botrytis cinere. Under wet conditions, infection often occurs on leves, especilly on the mrgins or tips nd cuses wtersoked lesions of vrious sizes (Figure 17). Fusrium root nd crown rot Fusrium spp. (root nd crown rot) re the most commonly encountered fungi in infected crowns nd roots (Figure 16). This disese usully occurs during the propgtion of echince y division of crowns nd roots. The fungi invde the wounded tissues in the crown or root res when divided plntings re grown in dmp medi. Figure 17. Botrytis light cuses rown lesions on leves of E. purpure. Figure 16. Crown nd root rot of E. pllid cused y Fusrium spp. Discolored lesions on the crown. Figure 16. Roots of E. ngustifoli ffected y crown rot cused y Fusrium spp. Roots hve ecome truncted nd severl hve disintegrted. Once the pthogen hs invded the midri or veins, it cn dvnce rpidly to the petiole nd stem, which results in the collpse of the whole lef. Lesions expnd rpidly. The pthogen produces profuse conidi nd myceli on the surfce of ded nd dying leves, stems nd lossoms (Figure 18). This results in moldy gry ppernce nd rpid disese spred. Fusrium oxysporum hs een isolted from discoloured vsculr undles of roots nd crowns, while F. solni hs een found in the cortex. Other species of Fusrium, such s Fusrium venceum nd F. equiseti, hve lso een isolted from disesed roots. Control mesures 1. Avoid injuring roots during cultivtion. 2. Do not overwter the growing medi, especilly during the first two weeks fter propgtion y division of the crown nd roots. 3. Use helthy plnts for propgtion. Figure 18. Infection y otrytis light cuses collpse of the petiole. Figure 18. Botrytis light lesions move up the petioles nd into the leves. Longitudinl lesions pper on the stems. Spores of Botrytis re unicellulr, smooth-wlled nd roughly ovl in shpe. 6

7 Under dry conditions, the disese develops slowly nd forms smll to lrge, rown or lck lesions or even ecomes quiescent. Lrge lesions often split leves or form holes in the center. Round, sphericl or irregulr microscleroti my e produced on ded or dying plnt prts. Although B. cinere does not usully kill coneflower plnts, it often hevily infects disc flowers nd young shoots. Therefore, otrytis light could ply significnt role in the productivity of this crop under cool, wet growing conditions in the greenhouse nd field. Control mesures 1. Prctice good snittion y removing infected plnt deris t the end of ech growing seson. 2. Grow plnts t proper spcing etween nd within the rows. Since echince plnts need three yers to rech the hrvest stge, proper spcing should e considered t plnting to improve ir circultion mong plnts. 3. Avoid wter condenstion in greenhouses. Use proper ventiltion systems nd wter plnts efore sunset. 4. No fungicides re currently registered in Cnd for the control of this disese. Figure 19. Alternri cuses drk lesions tht tend to follow midri in seedling leves. Figure 19. Alternri lef spot on E. ngustifoli. Lesions pper olong, light-colored in the centre nd re surrounded y drk, necrotic tissue. Alternri lef spot Alternri spp. infects leves cusing smll drk rownto lck-coloured spots (Figure 19), which cn grow together nd form lrge lesions under moist conditions. The inner tissue of lrge spot my fll out, leving hole in the lef. Alternri my lso infect young shoots nd smll flowering heds, resulting in die-ck symptoms (Figure 20). Alternri cn infect the seed nd ecome seed-orne pthogen. Occsionlly, the pthogen infects the root, crown nd leves of young seedlings, cusing root rot nd lef spots. Control mesures 1. Sterilize seeds with 1% lech solution for 3 to 5 minutes nd rinse them with sterile wter efore strtifiction or seeding. Figure 20. Alternri lef spot on E. ngustifoli. Lesions pper olong, light-colored in the centre nd surrounded y drk, necrotic tissue. Tissue in the centre my fll out to crete holes in the leves. Figure 20. Alternri lesions cuse collpse of the stem. 7

8 Prepred y: Kn-F Chng Ron Howrd Crop Diversifiction Centre S. Crop Diversifiction Centre S. Brooks, Alert Brooks, Alert Sheu-Fng Hwng Stn Blde Alert Reserch Council Crop Diversifiction Centre N. Vegreville, Alert Edmonton, Alert Finncil ssistnce to print this fctsheet ws provided y the Alert Reserch Council nd the Alert Agriculture Specil Crops Product Tem. Literture Cited 1. Chng, K.F., R.J. Howrd, nd S.F. Hwng First report of Sclerotini sclerotiorum on coneflower. Plnt Dis. 81: Chng, K.F., R.J. Howrd, R.G. Gudiel, nd S.F. Hwng First report of Botrytis light, cused y Botrytis cinere, on coneflowers. Plnt Dis. 81: Chng, K.F., R.J. Howrd, S.F. Hwng, R.G. Gudiel, S.F. Blde Diseses of Echince in Alert in Cn. Pl. Dis. Surv. 78: Hwng, S.F., K.F. Chng, nd R.J. Howrd Yellows diseses of echince, monrd nd crwy. Agdex 630-1, Agri-fx, Alert Agriculture, Food nd Rurl Development. 4pp. 5. Hwng, S.F., K.F. Chng, R.J. Howrd, A.H. Khdhir, R.G. Gudiel, nd C. Hiruki First report of yellows phytoplsm disese in purple coneflower (Echince spp.) in Cnd. J. Plnt Dis. Prot. 104: Peichowski, K., Rizvi, S., nd Reese, R.N First report of Fusrium oxysporum on purple coneflower. Plnt Dis. 81: M 8