Report 83-6 EVALUATION OF FUNGICIDES TO CONTROL BOTRYTIS BLIGHT IN WESTERN LARCH SEEDBEDS AT THE COEUR D'ALENE NURSERY, IDAHO ABSTRACT

Transcription

1 PRNG BNDER opertive orestry & Pest Mngement 51)11 M9 A3 yi, 8 3- Report 83-6 EVALUATN F FUNGCDES T CNTRL BTRYTS BLGT N WESTERN LARC SEEDBEDS AT TE CEUR D'ALENE NURSERY, DA 35 Mrch 1983 R. L. Jmes 1/, J. Y. Woo V, P. L. Mlone 2/ by ABSTRACT 1 Six fungicides were evluted to control Botrytis blight of western lrch in seedbeds t the Coeur d'alene Nursery. Fungicides were pplied t biweekly intervls during the spring of 1982; test seedlings were inoculted with spores of B. cinere twice during the evlution period. Seedling mortlity nd height were recorded in ctober just prior to lifting. Becuse of overll low infection levels, no differences in seedling mortlity were pprent s result of fungicide tretment. Low infection ws likely due to drier spring wether thn when outbreks of the disese previously occurred. Most fungicides decresed seedling height, lthough no externl indictions of phytotoxicity were pprent. Severl of the fungicides tested cn be considered for use to control Botrytis blight in lrch seedbeds. NTRDUCTN Western lrch (Lrix occidentlis Nutt.) is n importnt nd highly desirble conifer species in the Northern Region. Demnd for lrch seedlings for outplnting increses ech yer. Nursery seedling production is often limited by seed vilbility nd other problems such s diseses. ne of the serious diseses of lrch in nurseries is blight cused by Botrytis cinere (Fr.) Pers. This pthogen cuses folige nd twig blight tht my result in extensive seedling mortlity. Crops t the Coeur d'alene Nursery in both greenhouses (Jmes et l. 1982) nd seedbeds 1/ Plnt Pthologist, Coopertive Forestry nd Pest Mngement, Missoul, MT. 2/ Plnt Pthologist, ntermountin Forest nd Rnge Experiment Sttion, Moscow, D. 3/ Supervisory Forester, Coeur d'alene Nursery, Coeur D'Alene, D. United Sttes Forest Northern P.. Box 7669 Deprtment of Service Region Missoul, Montn Agriculture 5987

2 (Jmes 198) re often ffected by the disese. Western lrch is especilly susceptible to Botrytis blight becuse of the bundnce of ded 1P folige it produces nnully. The pthogen redily colonizes this necrotic tissue, nd then my spred to djcent helthy tissues, cusing ptches of seedling mortlity (Jrvis 198). Dmge is often severe under cool, wet conditions, especilly when seedling cnopies re full nd ir circultion mong plnts is reduced (Blkemn 198; Smith et l. 1973). Botrytis blight is often controlled in greenhouses by pplying fungicides periodiclly through overhed wtering systems (Gillmn nd Jmes 198; McCin 1978; McCin nd Smith 1978). Severl fungicides hve commonly been used ginst this disese. owever, the fungus my develop tolernce to some of these chemicls, especilly when one prticulr fungicide is pplied repetedly throughout the growing seson (Cooley 1981; Gillmn nd Jmes 198; Jmes nd Gillign 1983). Strtegies nd schedules for fungicide ppliction to control Botrytis blight in conifer seedbeds hve not been developed. Therefore, in this study we evluted the efficcy of severl fungicides commonly used in greenhouses to control the disese in seedbed environment. MATERALS AND METDS Fungicide evlution tests were conducted on western lrch seedlings during their second growing seson in seedbeds t the Coeur d'alene Nursery. Trees of pproximte uniform height nd density were selected for the evlution. Six fungicides previously tested in greenhouses (Jmes et l. 1982) were evluted (tble 1). Two formultions of chiorothlonil were tested becuse both hd previously been used opertionlly t the Nursery nd we wnted to find out if there were differences in seedling response to the two formultions. The checks consisted of pplying distilled wter to test seedlings. A rndomized block design ws used for the evlution. Ech tretment block consisted of.9 liner meters (3 feet) of seedbed (.95 m2-1.5 ft 2 ). A.3 m (1 ft.) untreted buffer strip seprted ech tretment block. Ech tretment nd the wter check were replicted 5 times (totling 135 blocks). Tretment blocks were delineted on the ground with wooden stkes t ech corner nd string tied between stkes. The number of test seedlings in ech block ws recorded t this time. Tretment blocks were clerly mrked so tht number of test seedlings in ech block t the beginning nd end of the test could be ccurtely compred. Seedlings in ech plot were treted with the pproprite fungicide or wter six times during the test period t pproximtely 2-week intervls commencing on Mrch 26, For ech tretment, pproximtely 9.5 liters (2.5 gl.) of fungicide solution or wter were pplied to seedlings in ech block so tht ll seedling folige ws thoroughly drenched. es 1

3 x.. c..) g p (.7 l P (71 l tt cn -7 ) 1 s-t o U - +; P-1 co tg-i o tr--1 cu i ) U ) -1-1 r. 2, V7 6 7 g,-+.1 i A co g.3..z C./ P ri $. ) U 3 ri - i- ) r- C.) 1 13 p Q)(1) C <C P, ri " CU 1 lj.1 (1) l 7,.) r PP it. o P o ) 1 $..o..j P c u.3 W C.1 ri _f- N W..). V PN ri P.ii P-. 9- Z. $..1 U t -1 g ) W r- ") n rl.1-)....t n Cn rl rl..r1 N N r-1 X q Z X l, V P 'C, rl X N.1 c" , 1 r 1 1.i n-t C..r1 -C X "71 5. un 1. W 1 e -, Z c) U W.) g "7 S U l c C ' 1-1 CU w.) 1 3 C c co '1z! U p -1 ) x-1 Z ). co 1- >-. - ) P C.) U.o V cd r. ctl C.) -3-

4 All test seedlings were inoculted with spore suspension of Botrytis to provide uniform exposure to the fungus. The B. cinere isolte used for inocultions (CD-16) ws obtined from n infected western lrch seedling growing in greenhouse t the nursery. This isolte hd been pthogenic to western lrch s indicted in previous greenhouse inocultion-fungicide tests (Jmes et l. 1982). Spore suspensions were prepred by dding 1 ml sterile distilled wter to 1-dy-old Botrytis cultures growing in petri dishes on potto dextrose gr. Spores were gitted with sterile cmel's hir brush. Spore suspensions were pssed through double lyers of cheesecloth to remove mycelil frgments. They were then brought to the desired concentrtion of bout 2.8 x 16 spores/ml by diluting with sterile distilled wter. Test seedlings in ech tretment block were spryed with 2 ml of the spore suspension using fine mist tomizer. Seedlings were initilly inoculted on April 1-15 fter they hd been treted with the fungicides twice. Ambient temperture ws bout 2 C nd the wether ws prtly cloudy nd windy. A month fter this inocultion, there ws little indiction of infection - this my be due to the dry, windy wether during nd shortly fter the inocultion period. Therefore, we scheduled second inocultion to coincide with period of cool, wet wether. The second inocultion ws conducted on My 27 during light rin with mbient tempertures from 5 to 1 C. Light rin continued for 2 dys following the second inocultion. The spores used in both inocultions were from the sme isolte, nd the spore concentrtions were lso the sme. The evlution ws concluded on ctober just prior to the trees being lifted. The number of live nd ded seedlings per plot ws tllied. We lso mesured the height of 1 seedlings in ech tretment block. These seedlings were concentrted in the center of ech tretment block to minimize possible border effects. Seedling survivl nd height dt were compred mong tretments with n nlysis of vrince. Significnt differences mong tretments were locted using Duncn's Multiple Rnge Comprison Test. RESULTS AND DSCUSSN ur results indicted very high seedling survivl in ll tretment ctegories (tble 2). Survivl ws even high (98.6 percent) in the wter tretment, indicting very low levels of infection. Seedling survivl differences mong tretments were not sttisticlly significnt (P =.5). 1

5 Tble 2.--Effects of fungicides on survivl of western lrch seedlings t the Coeur d'alene Nursery. Tretment No. ded seedlings 1 Averge percent survivl 2/ wter benomyl (Tersn 1991 ) iprodione (Chipco 2619 ) chlorothlonil (Dconil 2787) cptn (Cptn) diclorn (Botrn ) se chlorothlonil (Brvo 6F ) / The number of seedlings tht died between the initil count (3/3/82) nd the finl count (1/27-28/82). 2/ Mens were not significntly different (P =.5) using n nlysis of vrince. Percentges underwent rc-sin trnsformtions for dt nlysis. These low infection levels were disppointing becuse we hd expected significnt tretment differences bsed on previous tests in greenhouses (Jmes et l. 1982). Low infection resulted despite two inocultions of test seedlings. Wether conditions during the spring of 1982 were drier thn during the previous 2 yers. Since the environment in seedbeds is not s esily controlled s it is in greenhouses, success of our inocultions depended on mbient conditions. The initil inocultion ws conducted during dry, windy period in April. For successful infection, Botrytis spores need to lie in film of wter for t lest severl hours (Blkemn 198). Therefore, conditions were not conducive during nd shortly fter the first inocultion period, resulting in little infection. owever, the second inocultion ws conducted during cool, wet period in My nd this wet period ppered to hve persisted long enough for good infection. Despite these conditions which seemed to be idel, there ws little infection. We know tht the spores were vible. becuse they were tested for germintive cpcity on lbortory medi immeditely fter inocultion. After the second inocultion, light rin fell stedily for 2 dys, so it is possible tht mny of the spores were wshed from the seedling folige. Also, the My inocultion ws conducted lte in the spring, The fungus needs time to become estblished in infected tissues before onset of drier, summer-like wether. t is possible tht the fungus did not hve enough time to get estblished in the host fter the My inocultion. n ny event, the inocultions resulted in infection much below the desired nd expected levels.

6 Growth in seedling height during the second growing seson ws ffected by the fungicides (tble 3). Using the wter check s guide for norml seedling height, five of the six fungicides tested significntly reduced height growth of western lrch. Chlorothlonil (Brvo 61) ws the only fungicide tht stimulted seedling height. owever, the height of most of the treted seedlings ws well within the stndrds estblished by the Nursery. Severl of the tested fungicides cused similr effects on seedling height in previous greenhouse test (Jmes et l. 1982). owever, phytotoxicity s evidenced by tissue necrosis or premture needle bscission ws not found in either the seedbed or greenhouse tests. Tble 3.--Effects of selected fungicides on height of western lrch seedlings t the Coeur d'alene Nursery. Tretment Men height 95% (MM) 1 Confidence intervl wter C '359.3 benomyl (Tersn 1991 ) B iprodione (Chipco 2619) A chlorothlonil (Dconil 2787 ) 336. B cptn (Cptn) B diclorn (Botrn ) A chlorothlonil (Brvo 6F(D) 37.9 D / Mens followed by the sme cpitl letter re not significntly different (P =.5) using Duncn's Multiple Rnge Comprison Test. ur results indicte tht fungicide tretment of seedbeds to control Botrytis blight is necessry only if infection is common nd periods of cool, wet wether re expected. We suspect tht severl of the fungicides tested re effective nd could help reduce future losses from Botrytis. The tretment progrm should include severl fungicides used in rottion so tht the pthogen will hve less opportunity to form tolernt strins (Cooley 1981; Gillmn nd Jmes 198). ACKNWLEDGEMENTS We pprecite the ssistnce of C. J. Gillign nd M. Klontz for field dt collection, R. E. Eder for sttisticl nlysis, nd C. E. Chtterton for technicl dvice.

7 This publiction reports reserch involving pesticides. t does not contin recommendtions for their use, nor does it imply tht the uses discussed hve been registered. All, uses of pesticides must be registered by pproprite Stte nd/or Federl gencies before they cn be recommended. CAUTN: Pesticides cn be injurious to humns, domestic nimls, desirble plnts, nd fish or other wildlife--if they re not hndled or pplied properly. Use ll pesticides selectively nd crefully. Follow recommended prctices for the disposl of surplus pesticides nd pesticide continers.

8 LTERATURE CTED Blkemn, J. P Behviour of conidi on eril plnt surfces. n Coley- Smith, J. R., K. Verhoeff, nd W. R. Jrvis, eds. The biology of Botrytis. Acdemic Press, New York. pp Cooley, S. J Fungicide tolernce of Botrytis cinere isoltes from conifer seedlings. USDA For. Ser., Pcific Northwest Region. 13 pp. Gillmn, L. S. nd R. L. Jmes Fungicidl tolernce of Botrytis within Colordo greenhouses. USDA Tree Plnters' Notes 31(1): jmea, R. L Engelmnn spruce needle blight t the Coeur d'alene Nursery, dho. USDA For. Ser., Northern Region. Rept pp. Jmes, R. L. nd C. J. Gillign Fungicide tolernce of Botrytis cinere from the Flthed ndin Reservtion Greenhouse, Ronn, Montn. USDA For. Ser., Northern Region. Rept pp. Jmes, R. L., J. Y. Woo, nd J. F. Myers Evlution of fungicides to control Botrytis blight of continerized western lrch nd lodgepole pine t the Coeur d'alene Nursery, dho. USDA For. Ser., Northern Region. Rept pp. S. Jrvis, W. R Epidemiology. n Coley-Smith, J. R., K. Verhoeff, nd W. R. Jrvis, eds. The biology of Botrytis. Acdemic Press, New York. pp McCin, A Nursery disese problems-continerized nurseries. n Conference nd Workshop Proceedings, Western Forest Nursery Council nd ntermountin Nurserymn's Assocition, Eurek, CA. pp. B McCin, A.. nd P. C. Smith Evlution of fungicides for control of Botrytis blight of continer-grown redwood seedlings. USDA Tree Plnters' Notes. 29(): Smith, R. S., Jr., A.. McCin, nd M. D. Srgo Control of Botrytis storge rot of gint sequoi seedlings. Plnt Dis. Reptr. 57: