Needle damage development in Norway spruce seedlings as affected by humidity, temperature, and gray mold: a preliminary study

In e na ional Schola ly Resea ch Ne wo k ISRN Fo es y Volume 2012, A icle ID 810675, 9pages doi:10.5402/2012/810675 Resea ch A icle Needle Damage De elopmen in No way Sp uce Seedlings as A ec ed by Humidi y, Tempe a u e, and G ay Mold: A P elimina y S udy Raija-Liisa Pe ¨ ais ¨ o and Juha Heiskanen Suonenjoki Uni , Finnish Fo es Resea ch Ins i u e, 77600 Suonenjoki, Finland Co espondence should be add essed o Raija-Liisa Pe ¨ ais ¨ o, [email p o ec ed] Recei ed 30 Ap il 2012; Accep ed 4 June 2012 Academic Edi o s: A. San ini, A. Sca io , and P. Sme hu s Copy igh © 2012 R.-L. Pe ¨ ais ¨ o and J. Heiskanen. This is an open access a icle dis ibu ed unde he C ea i e Commons A ibu ion License, which pe mi s un es ic ed use, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed. Bo y is cine ea inocula ion on 3- and 6-mon h-old No way sp uce seedlings was es ed in combina ions o empe a u e (15 and 25◦C) and ela i e humidi y (50 and 80%) in a g ow h chambe . Occu ence o needle damage was examined 11 days a e he inocula ion. Damage occu ed mo e on inocula ed han on con ol seedlings. Needle damage ended o occu p opo ionally mo e on he olde seedlings and concen a ing mo e on he ops o he shoo in he younge seedlings. The highe empe a u e sugges ed sligh ly mo e damage occu ence han he lowe empe a u e did. The ela i e humidi y did no appea o co ela e wi h he damage ou b eak. Su ace we ness ended o inc ease he damage occu ence bu so did also he apou p essu e de ici . A he lowe ela i e humidi y, he seedlings had o be i iga ed mo e equen ly, which inc eased he su ace we ness. Thus, he esul s sugges ha any i iga ion me hod o o he condi ion con ol ha can p o ide low su ace we ness on seedlings dec eases needle damage by B. cine ea in o es nu se ies. 1. In oduc ion The g ay mold ungus (Bo y is cine ea Pe s.: F .) is a acul a- i e pa asi e. I li es as a sap ophy e on dead plan ma e ial and is also a plan pa hogen. The empe a u e op imum o g ay mold spo e ge mina ion and in ec ion is 9–21◦C, bu empe a u es be ween 2–25◦C a e also sui able o he ungus [1–4]. Rela i e humidi y g ea e han 98% and ee wa e a e op imal o spo e ge mina ion and mycelia g ow h o he B. cine ea ungus, o example, [5]. In Finland, No way sp uce (Picea abies (L.) Ka s .) is he p edominan species in o es nu se y seedling p oduc- ion. In ecen decades, con aine seedling p oduc ion has inc eased and he e has also been a subsequen inc ease in damage caused by g ay mold [6,7]. This inc ease is pa ly due o highe seedling densi ies and o mic oclima ic condi ions, which diffe om hose in ba e oo seedling p oduc ion. The damage may occu only ew days a e inocula ion on i al needles [8]. Visual symp oms a e spo s o discolo a ion usually in he middle o he needles o comple ely dead needles [8]. Nume ous s udies ha e been ca ied ou on g ay mold on ag icul u al c ops, while ewe s udies ha e deal wi h g ay mold on coni e seedlings, o example, Picea ma iana (Mill.) B.S.P, [9,10], Sequoiadend on gigan eum (Lindl.) Dene [11], Pseudo suga menziesii (Mi b.) F anco [5] 1988, and La ix occiden alis (Nu all) [12]. In he nu se y, g ay mold de elopmen is known o be dependen on he g ow h phase o he seedlings [8] bu also ma kedly on he ambien mic oclima e [13], effec o which is no s udied much wi h No way sp uce so a . The aim o his s udy was o su ey he effec s o ela i e humidi y and empe a u e and Bo y is cine ea inocula ion on needle damage ou b eak on i s -yea No way sp uce seedlings in he middle and a he end o he g owing season. Bioassays we e conduc ed in g ow h chambe s. 2. Ma e ials and Me hods 2.1. Seedling Ma e ial. The i s seedling se (se 1) was sown using seeds o egional o igin in a g ow h chambe 2ISRN Fo es y on 5 h Oc obe and he second one (se 2) on 18 h Oc obe 2001 in PL-81F con aine s (85 cm3con aine size, 81 con aine s pe ay, seedling densi y 546 m−2)(BCC Oy, Lannen Plan Sys ems, S¨ akyl¨ a, Finland) illed wi h low-humi ied sphagnum pea . Seedlings we e g own using no mal g owing p ocedu es as in ee nu se ies [14]. The use o mo e han one seedling se was necessa y because only wo smalle g ow h chambe s (i.e., wo empe a u e/ ela i e humidi y combina ions om he wan ed ou combina ions) we e a ailable simul aneously o condi ion ea men s a he same age o seedlings. Bo h seedling se s we e g own in a bigge g ow h cham- be (Type 10Sp/5 DU-Pi, Weiss Umwel echnik, Linden- s u h, Ge many) be o e mo ing hem in o smalle g ow h chambe s wi h diffe en ea men condi ions. In he bigge g ow h chambe , pho osyn he ically ac i e adia ion a he seedling shoo le el was 300–400 µEm −2s−1(abou one- hi d o hal o ull day ligh ) and empe a u e a ied du ing he day and nigh om 15.5 o 19.0◦C, and he ela i e humidi y 80–95%. The day and nigh hy hm was simula ed o co espond o he na u al g owing season, which mean dec eased empe a u e and inc eased ela i e humidi y du ing he nigh . To con i m ha g ow h hy hm o he seedling se s diffe ed o no om each o he , seedling heigh (Figu e 1(a)) was measu ed weekly on 4 andom ays ( om 8 seedlings pe ay) om he seedling se s 1 and 2. Seedling heigh and he numbe o needles we e measu ed a he age o 3 and o 6 mon hs on 4 ays ( om 5 seedlings pe ay) o he seedling se 1. A he seedling age o 3 mon hs, he mean alue (4 ays, 5 seedlings pe ay) o he o al numbe o needles pe seedling was 358.7 (sd 53.38), and he mean heigh o he measu ed seedlings 131.6 mm (sd 24.75). The co esponding alues a he age o 6 mon hs we e 383.2 (sd 32.06) and 140.1 mm (sd 18.16). On he basis o hese da a, he mean numbe o needles was es ima ed om he seedling heigh s (y=230.52 + 1.02 ∗heigh , R2=0.09, P=0.019) and was used o seedlings om he seedling se s 1 and 2. In addi ion, seedlings sown on 22nd Ap il 2002 (se 3) in a p oduc ion g eenhouse o he Suonenjoki Resea ch Uni we e used a age o 5 mon hs and 9 days and 5 mon hs and 24 days (handled as one age g oup). The heigh o hese seedlings was measu ed e e y second week du ing he g owing season on 4 ays ( om 9 seedlings pe ay) (Figu e 1(b)). The numbe o needles pe seedling was measu ed a an age o abou 6 mon hs on 4 ays ( om 5 seedlings pe ay). The mean numbe o needles was 740 pe seedling (sd 77.26) and he mean heigh o he seedlings was 193 mm (sd 34.75). The numbe 740 was subsequen ly used as an es ima e o he o al numbe o needles/seedling o hese seedlings. In all he seedling se s, he heigh g ow h s opped a he age o 4.5–5 mon hs (Figu es 1(a) and 1(b)). 2.2. Inocula ion. G ay mold isola e BcSjk1.1 is a monospo e cul u e, o igina ing om a diseased sp uce seedling om Suonenjoki in 1998. The isola e was s o ed in a deep eeze as mycelium in c yop o ec an (s e ile glyce ol and phospha e buffe ed saline, 1 : 4). Fo spo e p oduc ion, he isola e was g own on po a o dex ose aga medium o 3 days a 17◦C in he da k, hen o 3 days a 17◦C in he ligh , and inally s o ed a 4◦C un il needed. The spo es we e libe a ed by pipe ing s e ile wa e on o he ungal cul u e and b ushing he cul u e wi h a glass od. The wa e was hen il e ed h ough double gauze o elimina e mycelial ac ions. Fo he inocula ions, he spo e suspension was dilu ed o 1 × 106spo es pe mL. The inocula ion was made when he seedlings we e abou 3- and 6-mon h old (Table 1). The i s 4 ows o seedlings in each ay we e inocula ed (9 seedlings pe ow), and he seedlings in he las 4 ows we e used as a con ol. The i h seedling ow, ha is, he ow lying be ween ou inocula ed ows and ou uninocula ed (con ol) ows ac ed as a buffe zone. A plas ic bo le wi h he bo om emo ed was placed o e he seedling o be inocula ed. 3.2 mL o spo e suspension (1× 106spo es pe mL) was sp ayed on o each seedling (sp aye Bi chmeie , Fuxy, Swi ze land). The con ol seedlings we e sp ayed wi h wa e . The su ace o he g ow h medium was co e ed wi h a wa e -abso bing owel laye du ing inocula ion in o de o p e en he spo e suspension om in il a ing in o he pea . The inocula ed and con ol seedlings we e examined isually e e y second day o 11 days a e inocula ion. The damages we e colou -changed spo s on needles o comple ely dead needles [8]. The numbe and posi ion o needles wi h symp oms we e eco ded on each seedling. Le el o he damage was calcula ed as a pe cen age o damaged needles pe seedling. 2.3. Mic oclima ic T ea men s. A e inocula ion, he seedlings we e exposed o he ea men s in he wo smalle g ow h chambe s (Weiss Umwel echnik, Type 1600 Sp/+5···+45 DU-Pa), whe e he day leng h, empe a u e, and ela i e humidi y we e egula ed. The e we e ou ays (se 1 and se 3) o h ee (se 2) ays (81 seedlings pe ay) o each ea men ∗age combina ion (Table 1). Fo he seedling se 1, he ea men s we e 25◦C/80 RH, and 25◦C/50 RH, and seedling age 3 and 6 mon hs. Fo he seedling se 2, he ea men s we e 15◦C/80 RH and 15◦C/50 RH a seedling age 3 and 6 mon hs. Fo he seedling se 3, he ea men s we e 25◦C/80 RH, 25◦C/50 RH, 15◦C/80 RH, and 15◦C/50 RH a seedling age 5.3–5.8 mon hs (age handled as one age g oup). In he ea men s, empe a u e ac ually luc ua ed wi hin 25–30 (25) and 14–19◦C (15), and he ela i e humidi y wi hin 80–98 (80) and 37–55% (50) (Table 1). Ai empe a u e, ligh in ensi y, ela i e humidi y, and su ace we ness we e measu ed wi h senso s placed abou 2 cm abo e he pea medium. Vapou p essu e de ici was calcula ed om empe a u e and humidi y. Ai empe a u e and ela i e humidi y we e measu ed wi h HMP 133Y senso s (Vaisala, Helsinki, Finland), ligh in ensi y wi h LI- 190SZ quan um senso s (LI-COR, Lincoln, Neb aska, USA), and su ace we ness wi h Del a-T De ices senso s (Del a- T De ices, Camb idge, England). Tempe a u e, ela i e humidi y, and su ace we ness senso s we e connec ed o a ISRN Fo es y 3 Table 1: Ta ge alues and ac ual means o he ambien condi ions used in he ea men s in he space o g ow h chambe s and unde seedling oliage o he 11 days- es pe iods. Temp indica es empe a u e (◦C), RH ela i e humidi y (%), VPD apou p essu e de ici (kPa), and SW su ace we ness (mV). Seedling se Age, mon hs T ays/ seedlings Temp, ac ual Temp/RH a ge RH, ac ual VPD, ac ual Temp, oliage RH, oliage VPD, oliage SW, oliage 1 3 4/324 27.4 25/80 83.5 0.64 27.5 92.4 0.31 0.030 1 3 4/324 27.5 25/50 53.2 1.73 25.8 65.6 1.18 0.087 2 3 3/243 17.2 15/80 81.4 0.38 17.7 92.2 0.17 0.042 2 3 3/243 17.8 15/50 54.9 0.94 16.0 68.4 0.59 0.038 1 6 4/324 25.0 25/80 92.4 0.64 25.8 98.3 0.10 0.039 1 6 4/324 25.1 25/50 59.3 1.31 23.1 83.1 0.50 0.068 2 6 3/243 15.8 15/80 89.0 0.37 16.6 98.7 0.06 0.056 2 6 3/243 15.7 15/50 61.0 0.71 14.8 75.5 0.43 0.046 3 5.3 4/324 24.6 25/50 58.5 1.29 21.9 79.0 0.55 0.20 3 5.3 4/324 16.0 15/50 58.6 0.75 15.3 67.9 0.56 0.19 3 5.8 4/324 25.2 25/80 87.7 0.40 24.8 94.3 0.18 0.07 3 5.8 4/324 16.4 15/80 78.5 0.40 15.8 90.5 0.17 0.16 4ISRN Fo es y Heigh (mm) 0 20 40 60 80 100 120 140 160 180 Seedling se 1 Seedling se 2 Days a e sowing 0 20 40 60 80 100 120 140 (a) Days a e sowing 0 20 40 60 80 100 120 140 Heigh (mm) 20 40 60 80 100 120 140 160 180 200 220 Seedling se 3 (b) Figu e 1: (a) Heigh de elopmen in he seedling se s 1 (•) and 2 (o). (b) The heigh de elopmen in he seedling se 3. Campbell da a logge (CR10X, Campbell Scien i ic, Lough- bo ough, England), which was se o e ie e da a e e y 5 minu es. 2.4. Da a Analysis. The numbe o needles in ec ed by g ay mold was calcula ed pe seedling and used as he numbe o as he pe cen age o he o al es ima ed needle numbe pe seedling a a gi en g ow h s age. The ays o each ea men we e comple ely andomized. The da a analysis was done wi hin each seedling se . Diffe en seedling se s wi h diffe en empe a u e and humidi y combina ions we e used because he e we e only wo g owing chambe s simul- aneously. GLM uni a ia e ANOVA p ocedu e and Tukey’s es in he s a is ical so wa e SPSS 11 we e used. Condi ion ea men , inocula ion, and seedling age we e used as ixed ac o s and ay as a andom ac o . P io o ANOVA, a csin ans o ma ion was no needed o pe cen age alues because he o al numbe o needles was much g ea e han he numbe o needles in ec ed. Also he numbe o seedlings was la ge enough. 3. Resul s The p opo ion o damaged needles was no signi ican ly affec ed by ea men s 25/80 and 25/50, bu i was affec ed by inocula ion (P<0.001) and age o seedling (P<0.001) in seedling se 1. The damage p opo ion was bigge in inocula ed seedlings han in con ol and bigge a age o 6 mon hs han a age o 3 mon hs o seedlings (Table 2(a), Figu e 2). A seedling age o 6 mon hs wi h ea men 25/50 and a he seedling age o 3 mon hs wi h ea men 25/80, he inocula ion inc eased needle damage mos clea ly. The pe cen age o damaged needles was also no affec ed by he ea men s 15/80 and 15/50 (seedling se 2) bu affec ed by inocula ion (P<0.001) and also by age (P<0.01), olde seedlings we e mo e damaged (Table 2(b), Figu e 2). T ea men s (25/50, 15/50, 25/80, and 15/80, seedling se 3) affec ed signi ican ly (P<0.001) and inocula ion inc eased he needle damage (Table 2(c), Figu e 2). Di - e ences we e ound be ween ea men s 25/50 and 15/50 (P<0.05), bu no be ween ea men s 25/80 and 15/80. In ea men 25/50, he damage pe cen age was highe and i diffe ed om all he o he ea men s (25/80, 15/50, 15/80) (P<0.003) (Figu e 2). The pe cen age o damage needles inc eased almos linea ly du ing he 11-day pe iod (Figu e 2). In he case o inocula ed 3- and 6-mon h-old seedlings, abou 40–50 and 20% o all he damaged needles, espec i ely, we e si ua ed a he op o seedlings in seedling se s 1 and 2 (Figu e 3). In ea men s wi h seedling se s 1 and 2, he empe a u e o 25◦C was somewha mo e a o able o damage occu - ence han he empe a u e o 15◦C(Figu e 4). The ela i e humidi y (53–92%) did no appea o be co ela ed wi h ou b eak o he damage (Figu e 4). Su ace we ness ela ed posi i ely o he damage occu ence, as was he case also o apou p essu e de ici (Figu e 4). The effec seemed o be clea e on 6-mon h-old han on 3-mon h-old seedlings. The su ace we ness a an age o 3 mon hs was in ac highe han hose shown, while he senso s did no imely con ac wi h he i iga ion wa e . Fu he mo e, ela i e humidi y measu ed wi hin he seedling canopy in he g ow h chambe diffe ed om hose ou side he canopy ela i e humidi y was 6–24% uni s g ea e wi hin he seedling canopy. The ela ionships be ween he p opo ion o damaged needles and he ambien condi ions in noninocula ed ISRN Fo es y 5 Damaged needles (%) 0 1 2 3 4 5 6 T ea men s Seedling se 1 25/80 25/50 25/80 25/50 Inocula ed Con ol Damaged needles (%) 0 1 2 3 4 T ea men s Seedling se 2 15/80 15/50 15/80 15/50 Inocula ed Con ol Damaged needles (%) T ea men s 0 1 2 3 4 5 Seedling se 3 25/50 15/50 25/80 15/80 Inocula ed Con ol (a) Damaged needles (%) 0 1 2 3 4 5 6 0246810 25/80, 3 mon hs 25/50, 3 mon hs 25/80, 6 mon hs 25/50, 6 mon hs Days a e inocula ion Damaged needles (%) 0 1 2 3 4 15/80, 3 mon hs 15/50, 3 mon hs 15/80, 6 mon hs 15/50, 6 mon hs 0246810 Days a e inocula ion Damaged needles (%) 0 1 2 3 4 5 0246810 Days a e inocula ion 25/50, 5.3 mon hs 15/50, 5.3 mon hs 25/80, 5.8 mon hs 15/80, 5.8 mon hs (b) Figu e 2: (a) The pe cen age o damaged needles on he inocula ed and con ol seedlings as mean o ay means. In he seedling se s 1 and 2, he i s wo g oup ba s deno e 3-mon h-old seedlings and he second wo g oup ba s 6-mon h-old seedlings. In seedling se 3, he seedlings we e 5.3 and 5.8 mon hs old. (b) The pe cen age o damaged needles on inocula ed seedlings 1–11 days a e inocula ion. 6ISRN Fo es y Table 2: Uni a ia e analysis esul s o he effec s o ea men , age, and inocula ion on he pe cen age o damaged needles pe seedling (a) in seedling se 1, ea men s 25/80 and 25/50 o 3- and 6-mon h- old seedlings. (b) In seedling se 2, ea men s 15/80 and 15/50 o 3- and 6-mon h-old seedlings. (c) In seedling se 3, ea men s 25/50, 15/50, 25/80, and 15/80 o 5.3- and 5.8-mon h-old seedlings. (a) Sou ce d MS FP In e cep 1 153.27 167.44 0.000 Inocula ion 1 11.50 95.92 0.000 Age 1 15.80 17.26 0.001 T ea men 1 0.27 0.30 0.595 Inocula ion ∗age ∗ ea men 1 0.83 6.96 0.022 Inocula ion ∗age 1 1.71 14.27 0.003 Inocula ion ∗ ea men 1 0.39 3.25 0.097 Age ∗ ea men 1 0.08 0.09 0.769 Age ∗ ea men ∗ ay 12 0.915 7.64 0.001 (b) Sou ce d MS FP In e cep 1 53.97 120.13 0.000 T ea men 1 0.00 0.00 0.957 Age 1 5.09 11.33 0.010 Inocula ion 1 4.99 34.59 0.000 T ea men ∗age ∗inocula ion 1 0.01 0.06 0.815 T ea men ∗age 1 0.02 0.03 0.859 T ea men ∗inocula ion 1 0.11 0.73 0.419 Age ∗inocula ion 1 0.18 1.24 0.298 Age ∗ ea men ∗ ay 8 0.45 3.12 0.064 (c) Sou ce d MS FP In e cep 1 106.576 538.389 0.000 T ea men 3 2.535 12.806 0.000 Inocula ion 1 1.682 6.994 0.021 T ea men ∗inocula ion 3 0.105 0.437 0.730 T ea men ∗ ay 12 0.198 0.823 0.629 seedlings we e simila o hose in he inocula ed seedlings (Figu e 4), bu wi h sligh ly smalle p opo ion o damaged needles (Figu e 2). In ea men s wi h seedling se 3, he mean ela i e humidi y was 59–88% (Table 1,Figu e 4). The su ace we - ness showed a posi i e co ela ion wi h he damage occu - ence, while ela i e humidi y was nega i ely co ela ed. A empe a u eo 25 ◦C was somewha mo e a o able o occu ence o he isible damage han a empe a u e o 15◦C (Figu e 4). Vapou p essu e de ici co ela ed posi i ely wi h he needle damage. 4. Discussion Bo y is cine ea is a e y common ungus also in o es nu se ies. The mic oclima ic condi ions p e ailing a e B. cine ea spo e in ec ion a e impo an o needle damage Damaged needles on he op, pe cen om all damaged needles 0 10 20 30 40 50 60 Seedling se 1 25/80 25/50 25/80 25/50 3-mon h old 6-mon h old (a) Damaged needles on he op, pe cen om all damaged needles 0 10 20 30 40 50 60 Seedling se 2 15/80 15/50 15/80 15/50 3-mon h old 6-mon h old (b) Figu e 3: The p opo ion o damaged needles loca ed on he op o he seedlings a seedling ages o 3 and 6 mon hs. occu ence, in addi ion o he suscep ible g ow h phase [8], win e s o age [13], and p edisposi ion o seedlings, o example, by d ough and shading [10]. Du ing seedling p oduc ion, spo es o he ungus [5]ha ebeen oundmo e equen ly in ee seedling g eenhouses owa ds he au umn. In he p esen s udy, he uninocula ed seedlings also bo e needle damage bu less han he inocula ed seedlings. The diffe ence o needle damage equency be ween inocula ed and uninocula ed seedlings ob iously means B. cine ea success ul in ec ion, bu i was no e i ied by eisola ions. In he p esen s udy, he empe a u e o 25◦Cp o ed o be mo e a o able han ha o 15◦C o g ay mold in ec ion in No way sp uce seedlings. Bo h hese empe a u es a e ISRN Fo es y 7 0 1 2 3 4 5 10 15 20 25 30 Damaged needles pe seedling (%) Tempe a u e in g ow h chambe (◦C) (a) 0 1 2 3 4 5 50 60 70 80 90 100 Damaged needles pe seedling (%) RH in g ow h chambe (%) (b) 0 1 2 3 4 5 Damaged needles pe seedling (%) VPD in g ow h chambe (kPa) 3-mon h-old seedlings 6-mon h-old seedlings 5.3 o 5.8-mon h-old seedlings 0 0.5 1 1.5 2 (c) 0 1 2 3 4 5 Damaged needles pe seedling (%) SW unde oliage (mV) 3-mon h-old seedlings 6-mon h-old seedlings 5.3 o 5.8-mon h-old seedlings 0 0.05 0.1 0.15 0.2 (d) Figu e 4: Rela ionships be ween empe a u e, ela i e humidi y (RH), and apou p essu ed de ici (VPD) in he g ow h chambe ai space and su ace we ness (SW) unde he oliage wi h he pe cen age o damaged needles 11 days a e inocula ion in he diffe en ea men s wi h diffe en seedling ages. close o hose epo ed in he li e a u e o op imum g ay mold spo e ge mina ion and in ec ion in o he hos plan s 10–21◦C[2,15], 18–25◦C[4], 11–16◦C, o 11–25◦C, depending on he in ec ion phase [16]. The inc ease in su ace we ness ended o inc ease he occu ence o he damage. When he ela i e humidi y was lowe (50%), he seedlings had o be i iga ed mo e equen ly han a highe humidi y. The spo es equi e ee wa e o ge mina ion and g ow h. Co espondingly, he con adic ion be ween he effec s o a apou p essu e de ici and ela i e humidi y on he le el o needle damage is due o he mo e equen i iga ion unde high e apo anspi a ion condi ions. Wi h o he hos s, i has been ound ha he ela i e humidi y mus be nea o 100% o wa e o he wise a ailable (as su ace we ness) o B. cine ea in ec ion o occu [4,13,17]. In p ac ice, ain and o e head i iga ion cause su ace we ness on he plan . Ou esul s sugges ha he isk o g ay mold damage could be educed by a anging i iga ion insuchaway ha su acewe nessdoesno p e ail o a oo long pe iod o ime. This could be done by choosing an app op ia e i iga ion sys em (o e head, d ip, o capilla y 8ISRN Fo es y i iga ion) and/o by adjus ing he iming and d op size o i iga ion. In an epidemiological sense, he occasional occu ence o low ela i e humidi y also migh ha e an inc easing effec on he disease occu ence, because ai -bo ne spo e dispe sion is also acili a ed a a low ela i e humidi y [16,18]. On he o he hand, du ing i iga ion, he spo e numbe in he ai can inc ease as a esul o he mechanical o ces imposed by wa e d ops [5]. The ele en-day ollow-up pe iod a e inocula ion used he e migh be oo sho . By ex apola ing he esul s, i can be assumed ha he diffe ences be ween some o he ea men s may ha e inc eased a e 11 days. In addi ion, a la en pe iod a e inocula ion is possible [16,19]. Howe e , he ends o damage occu ence in he 11-day pe iod a e inocula ion make i possible o d aw some conclusions: a empe a u e o nea 20◦C and su ace we ness a e condi ions a ou ing damage occu ence du ing sho pe iods. The needle damage occu s p opo ionally mo e on he ops, which is mo e ha m ul [13], o he shoo in h ee-mon h-old seedlings han in olde seedlings. The heigh g ow h o he olde seedlings s opped be o e he inocula ion, which mos p obably is a eason o p opo ionally less damage on he ops a his age. In he s udy o Pe ¨ ais ¨ o e al. [8], he effec o B. cine ea inocula ion a he a ious age o seedlings in g eenhouses began o dec ease a e abou 4 mon hs seedling age, bu he empe a u e and VPD alues co ela ed wi h he seedlings age. This ecen s udy wi h egula ed empe a u e and humidi y gi es p elimina y in o ma ion abou g ay mold and mic oclima e combina ions a a ious seedling ages. Nowadays, many sowing imes may be used du ing he g owing season and so also he seedling g ow h phases diffe mo e a he same ime poin /and mic oclima e condi ion. In conclusions, he needle damage by B. cine ea occu s p opo ionally mo e on he olde age o seedlings bu mo e on he ops (younges pa s) o younge seedlings. Su ace we ness and highe empe a u e and highe apou p essu ed de ici sugges ed inc eased needle damage, and damage was mo e equen in inocula ed han in con ol seedlings in his s udy. The e o e, i iga ion me hods o o he condi ion con ols ha can dec ease he su ace we ness could dec ease he needle damage caused by B. cine ea in o es nu se ies. Howe e , o de i ing mo e conclusi e esul s and implica ions, la ge ully ac o ial s udies in g ow h chambe s and in g eenhouses a e equi ed in he u u e. Acknowledgmen s The au ho s would like o hank he s affo he Suonenjoki Resea ch S a ion, especially Ee a Veh il¨ ainen and Jukka Lai inen, o echnical assis ance. Thanks go o Ris o Rikala o commen s on he s udy, o Juha Lappi o commen s on he da a analysis, and o Ma ja Po e i o eading and commen ing on he pape . The Founda ion o Resea ch o Na u al Resou ces in Finland suppo ed he s udy. Re e ences [1] Y. 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