The effect of disinfectants on fungal diseases of cucumber Hanna Avikainen, Hilkka Koponenand Risto Tahvonen Avikainen, H., Koponen, H. & Tahvonen, R. 1993. The effect of disinfectants on fungal diseases of cucumber. Agric. Sei. Finl. 2: 179-188. (Dept. PI. Biol., P.0.80x 28, FIN-00014 University of Helsinki, Finland and Agric. Res. Centre of Finland, Inst. PI. Protect., FIN-31600 Jokioinen,Finland.) Formaline, lobac P, sodium hypochlorite (NaOCl), Korsolin and Menno-Ter-forte were effective disinfectants in the control of damping-off (Pythium sp.) from peat substrate. Ipasept, Sanisept and Virkon S(1%) were shown ineffective against Pythium sp. in peat. Only formaline was effective in the control of black root rot (Phomopsis sclerotioides) from peat. In sand substrate P. sclerotioides could be eradicated also with sodium hypochlorite. Verticillium wilt (Verticillium dahliae) from peat substrate could be controlled with formaline, lobac P, sodium hypochlorite and Virkon S. Formaline and sodium hypochlorite were effective against Verticillium wilt in sand. Black stem rot (Didymella hryoniae) was susceptible to all disinfectants tested. Key words: Didymella bryoniae, disinfection, Phomopsis sclerotioides, Pythium sp., Verticillium dahliae Introduction The production of cucumber starts in Finland by growing seedlings in artificial light at the end of December. The greenhouses must be clean and free of diseases and pests in order to get high quality seedlings. Either new peat or rock wool is used as seedling growth substrate. One of the major risks is the damping-off. The cultivation is continued at the end of January in normal greenhouse conditions using as growth substrate rock wool or new peat isolated from ground soil with a plastic sheet or plastic bags. The major diseases are various root diseases and stem and leaf diseases during the growing season. Therefore the growing places must be free from diseases and pests before planting the seedlings. It is very common that farmers change plants during the summer to get a higher yield and a better quality in autumn. The risk of severe dis- ease infection is great, because diseases may spread with plant debris from old to new plants. Pythium sp., which causes damping-off, is a major problem in cucumber cultivation in Finland. Also black stem rot (Didymella hryoniae) is com- mon and difficult to control. Black root rot (Pho- mopsis sclerotioides) and Verticillium wilt (Ver- ticillium dahliae) are severe diseases of cucumber (Fletcher 1984).Black root rot is a very common disease on cucumber in Finland (Murman 1992). Verticillium wilt causes losses in open fields in southwestern Finland and in some cases in green- houses in western Finland (Tahvonen 1987). There are no resistant cultivars or effective fungi- cides to control these diseases. Disinfection of the soil has previously been in- vestigated as a means to control fungi (LINNA- SALMI 1955). Today, the growth substrate is changed every year (Murman 1992), which makes 179 Agric. Sei. Finl. 2 (1993) https://www.c-info.fi/en/info/?token=mTIiCRvZE1BSOIef.RoR_S3D5GOGN9zi0OgaB-Q.d9BElOsnIva5ldrB9Z8lUNBs4Oq_wmAo6qD0LF3EMRW69_A2xXkv6svaSo49mfIsEu5ozlxrXkoa0I8laOUklw5LWfdtgbc7yL65RgNvnYXzAPaskaECrQqNxZNRtPWM8289Bp9RadAje6zFg51SgAZ7QaHEM0THFJsUsv3N9pDitImeGZ90XbUQiVrRwZje1Klwxy4h5JzA9IXMjpkPAXJ4xyI5YUiD5nwgpcAHRivxaINpCe5tGqKKOyD1eDqQ_d6GlIVubfgnEO0e-3reazjR8KechFC58T8LgwZnxOseJht1GV0PAA 2 Table 1. The disinfectants, their active substances and the concentrations recommended by the manufacturers. Disinfectant Active ingredient, % Recommended concentration, % Desinfektol EL Ethanol, 60 undiluted Formaline Formaldehyde, 37 lobac P lodine, 1.8 5.0 3.0 Ipasept Quaternary ammo- 2.0 nium compounds, 2.8 Korsolin Glutaraldehyde, 10 Menno-Ter-forte Quaternary ammo- 1.0 1.0 nium compounds, 32.5 Sanisept Quaternary ammo- 2.0 nium compounds, 2.5 Sodium hypo- Active chlorine, 10 chlorite (NaOCl) 10.0 Taloset Quaternary ammo- 2.0 nium compounds, 3.5 Virkon S Potassium peroxysul- 1.0 phate, 60 disinfection ofsoil unnecessary. The pathogens do, however, survive in plant debrisand in soil particles as well as in the greenhouse structures for a long time. Disinfection of the structures and equipment is therefore still necessary. This disinfection study was carried out in 1988- 1990 to establish the applicability of different dis- infectants in plant production and their effect on fungal pathogens of cucumber. The research is part of a study carried out jointly by the University of Helsinki, the Technical Research Centre ofFinland and the Agricultural Research Centre. Material and methods Disinfectants and fungi Ten commercial disinfectants were tested on fungal pathogens of cucumber (Table 1). The concentra- tions recommended by the manufacturers were used in the trials. Any deviations from these con- centrations are given in the tables.The disinfectants were diluted in tap water. The tested fungi were Didymella bryoniae, Pho- mopsis sclerotioides, Pythium sp. and Verticillium dahliae. The names of the fungi are according to Table 2. The growth media used in the fungal cultures. Growth mediumFungus Didymella bryoniae Com mealagar (Difco) + 100 ppm streptomycin sulphate Phomopsis sclerotioides Malt extract agar (Difco) Com meal agar (Difco)+ 100ppm streptomycin sulphate Pythium sp. Martin’s medium Verticillium dahhae Com meal agar (Difco)+ 100ppm streptomycin sulphate Domsch et al. (1980). The fungal isolates included in the study were obtained the collections of the Institute of Plant Protection of the Agricultural Re- search Centre. The fungi were cultivated on differ- ent media depending on the fungus (Table 2). The formulas for culture media offungi are presented in Booth (1971). The effect ofdisinfectants on Pythium, Didymella and Verticillium in peat and plant debris in laboratory experiments The effect ofconcentration and disinfection time in the control of cucumber pathogens in peat and plant debris was investigated in laboratory trials. In test- ing Pythium sp. and V. dahliae the method used for testing the effect ofdisinfectants on Fusarium cul- morum and F. oxysporum in peat was used (KOPO- NEN et al. 1993). However, the amount of peat mixed in disinfectant was 1 g and 5 g in the V. dahliae trial and the exposure time was 15 and 60 min. In theD. bryoniae trial, the inoculate used was obtainedby mixing five infected pieces (about 5 cm long) of cucumber stem and 200 ml of disinfection dilution (N and 10' 1 N) with a homogenizer. The disinfectants were allowed to act for 10 and 100 min. Filtering and fungal cultivation were carried out as above in the Pythium and V. dahliae experi- ments. The effect of the disinfectants on D. bryoniae, Pythium sp. and V. dahliae on plastic surfaces con- taminated with fungus-peat or plant debris mixture was investigated in a laboratory trial. The trial was carried out as described in Koponen et al. (1993), 180 Agric. Sd. Finl. 2 (1993) testing the effect of disinfectants on Fusarium cul- morum and Botrytis cinerea on polyethene surface. All the above trials were made with three repli- cates. The plates were evaluatedafter one and three weeks. The results were calculated as efficiency percentages, i.e. the proportion ofhealthy pieces on agar plates of all pieces. The effect of disinfectants on pathogens in greenhouse experiments Peat experiment on Pythium In the Pythium trial, the plastic pots were contam- inated by growing in them infected cucumber seed- lings for 5 weeks. The cucumber seedlings were inoculated with naturally infected Pythium peat (20 g oat flour/1 1 peat). When the seedlings were in- fected and started to wilt, the growth substrates were allowed to dry.The pots were emptied and the dry peat debris (1-2 g) was washed with disinfec- tion solution using a brush and a propane sprayer (pressure of 4 bar). After 30 min the wash suspen- sion (300-400 ml) was filtered. The filter paper with peat was mixed in 200 ml of water with a homoge- nizer and the mixture was used for biotests. In the biotest, cucumber seedlings cv. ‘Dale- va’ (7 days old) were used as test plants. The mixture (10 ml) was applied onto the oat-peat collar around the base of the seedlings. The first 24 hours the cucumbers were kept in the dark at + 12-15°C, thereafter at 20°C in greenhouse with a light period of 12 hours (Bouhot 1975 a, b). There were four replicates, with five seedlings per treatment. Observations on the infected and dead plants were made daily four days after the treatments. The cucumbers were grown for 15 days. At the end of the trial the damage caused to the seedling and the roots was evaluated on a rating scale of 0-3: o=healthy plant, l=slightly infected base, 2=off-white and browned roots, and severely browned base, 3=wilted seedling and dead roots. The efficiency percentage of the disinfectants was calculated by comparing the severity of damage to the healthy and affected control using the formula: efficiency % = -—7 • 100a-h a=severity of infection in healthy control b=severity of infection in water control c=severity of infection in disinfection treatment. Peat experiment on Phomopsis and Verticillium The effect of disinfectants on P. sclerotioides and V. dahliae in peat was investigated by mixing 100 ml of fungus-peat (one Petri dish culture of fungi/100 ml water/1 I peat) inoculate in 2 1 of diluted disinfectant. The disinfection solution with peat was fdtered after 60 min and the peat was rinsed twice with water. Treated peat (3 g) was placed on the bottom of the pots. The pots (11) were filled with clean peat. As test plants were used two-day-old pregerminated cucumber seeds which were grown for 4-6 weeks, or one-week-old seed- lings grown until fruit production (about 10 weeks). The number of replications was three with three plants per treatment. At the end of the trial the severity of damage in the shoots and roots was evaluated on a rating scale of 0-3: o=healthy, l=slightly infected base and roots, 2=partly wilted leaves and roots, 3=dead plant. The efficiency percentage was calculated from the mean of the trials, comparing the effect of the disinfectants on thehealthy and infected control like in the Pythium trial. The viability ofV. dahliae on the cucumber stem was determined in laboratory. Pieces (5 cm) were taken from the base of the shoot. From thesepieces were cut small pieces (0.5 cm) and placed on com meal-streptomycin medium, four pieces per plate, and three plates per plant. The fungi grown on the pieces were evaluated after one and three weeks. The efficiency percentage was calculated as the proportion of healthy pieces of all pieces. Sand experiment on Phomopsis and Verticillium The effect of the disinfectants on P. sclerotioides and V. dahliae in sand was also investigated. The sand was inoculated by mixing fungal suspension (one fungus culture/100 ml water) in 1 1 of sand. 181 Agric. Sei. Finl. 2 (1993) Table 3. The effect of concentration and disinfection time on Pythium sp. in peat debris. Disinfectants and concentrations (N): 1 = formaline (5%), 2= lobac P(3 %), 3= Ipasept (2 %), 4= Korsolin (1 %), 5= Menno-Ter-forte (1 %), 6 = NaOCI (10 %) and 7 =Virkon S (2 %). Concen- Peat Time, Disinfectant tration of g/1 1 min 1 2 3 4 5 6 7 disinfectant disinfectant Efficiency % Concentration (N) 1 1 42 100 100 100 100 100 92 10 92 100 100 100 100 100 100 100 100 100 100 100 100 100 100 0.1 1 58 100 100 100 UK) 100 KM) 10 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 10' N 1 1 92 100 0 100 16 67 10 100 100 0 100 63 92 100 100 100 92 100 91 100 0.1 1 - 100 100 100 100 83 1(X) 10 100 67 100 100 100 100 100 - 100 92 100 100 100 100 Table 4. The effect of concentration and disinfection time on Verticillium dahliae in peat debris. Disinfectants and concentra- tions (N): 1= formaline (5 %), 2= lobac P (3 %), 3= Ipasept (2 %), 4= Menno-Ter-forte (1 %), S=NaOCI (10 %), 6 = Taloset (3 %), 7 =Virkon S (2 %). Concen- Peat Time, Disinfectant tration of g/1 1 min 12 3 4 5 6 7 disinfectant disinfectant Efficiency % Concentration (N) 5 15 100 0 0 42 17 17 67 60 100 50 0 92 58 17 92 1 15 75 33 8 25 50 0 92 60 92 8 0 92 92 0 100 10' N 5 15 100 0 0 0 0 0 92 60 100 0 0 0 0 0 67 1 15 67 0 0 0 0 0 67 60 100 0 0 17 8 0 42 One litre of inoculated sand was put into plastic pots and 60 ml (approx. 4 1/m ) of disinfection dilution was sprayed onto the sand surface. After one hour of treatment the sand was washed with water and filtered. The holes in the peat substrate were filled with 30 g of treated sand and the one- week-old cucumber seedlings were planted there. The number of replications was three or five with three seedlings per treatment. At the end of the trial (3-5 weeks) the severity of damage to shoots and roots was evaluated as above in the peat experiment on Phomopsis. The trial was repeated three times on P. sclerotioides and twice on V. dahliae. The results were calculated in the same way as in the peat trials on Pythium. Analysis of variance was used in the statistical analysis of the results. Significances were tested with Tukey’s test. 182 Agric. Sei. Finl. 2 (1993) Table 5. The effect of disinfectants on Didymella kryoniae in cucumber debris. Treatment Concentration Disinfection time, min % 10 100 Efficiency % Water 0 0 lobacP 1 83 92 0.1 0 0 Ipasept 2 100 100 0.2 0 0 Korsolin 2 100 100 0.2 8 0 Menno-Ter-forte 1 100 100 0.1 92 42 NaOCl 10 100 100 1 75 100 Results In the laboratory experiment, all tested disinfect- ants were effective against Pythium sp. in peat debris when recommended concentrations were used. Even one minute treatment time was suffi- cient for all disinfectants except formaline and Virkon S. Menno-Ter-forte, Ipasept and lobac P were effective against Pythium sp. (Table 3) at a lower than the recommended concentration. Laboratory trials showed that Verticillium dahliae in peat debris was difficult to eradicate; only formaline was effective against this species. Virkon S and Menno-Ter-forte were also rather effective when the influence time was 60 min. lobac P and Ipasept were the weakest disinfect- ants (Table 4). All the tested disinfectants were rather effect- ive against Didymella bryoniae in plant debris at recommended concentrations when 10 min treat- ment time was used. Only 1% lobac P did not eradicate completely D. bryoniae (Table 5). Soaking the plastic pots contaminated with peat and fungus for 15-60 min in the disinfectant was sufficient to eradicate D. bryoniae and Py- thium sp. but not V. dahliae. However, Ipasept and Sanisept were ineffective against Pythium sp. and Ipasept against D. bryoniae (Table 6). V. dahliae was more difficult to eradicate than Py- thium sp. and D. hryoniae. However, lobac P and NaOCl eradicated V. dahliae perfectly after 15 min treatment time. Also the effect of formaline, Korsolin and Menno-Ter-forte on this fungus was over 90 % after 60 min treatment time (Table 6). In the greenhouse experiment, disinfestation of Pythium sp. from the surface of plastic pots was the most successful with formaline, lobac P, Kor- solin, NaOCl and Menno-Ter-forte. Ipasept, Table 6. The effect of disinfectants on fungi on the surface ofplastic pots contaminated with peat-fungus mixture. Treatment Concentrations Didymella Pythium sp. Verticillium % bryoniae dahliae Minimum time min/efficiency % Water 60/0 60/50 60/17 Formaline 5 15/100 15/100 60/92 lobacP 3 15/100 15/100 15/100 Ipasept 2 60/58 60/17 60/83 Korsolin 1 15/100 60/100 60/100 Menno-Ter-forte 1 15/100 60/92 60/92 NaOCI 10 15/100 60/100 15/100 Sanisept 2 15/100 60/42 60/58 Taloset 3 60/92 - 60/75 VirkonS 2 15/100 15/100 60/75 183 Agric. Sei. Fin!. 2 (1993) Table 7. The effect of disinfectants on Pylhium sp, in peat debris. Cucumber seedlings were used as test plants. Disease index: 0= healthy, 3= dead. Treatment Disease index, 0-3 Efficiency % Trial 1 Trial 2 Trial 1 Trial 2 Healthy control 0 a 0 a Water 2.60 b 2.34 b Formaline - 0.25 a - 89 lobacP 0.15 a 0.10 a 94 96 Ipasept 1.95b 25 Korsolin 0.20 a 92 Menno-Ter-forte 0.05 a 0.45 a 98 81 NaOCl 0.05 a 0.60 a 98 74 Sanisept 2.20 b 15 VirkonSl* - 1.88 b - 20 F-values 58.98*** 19.29*** Values in columns marked with the same letter do not differ at P=0.05. ***=P 0.001 Table 8. The effect of disinfection on Phomopsis sclerotioides in peat debris. Trials 1-2 lasted about 5 weeks, trials 3 and 4 until at fruit production. Disease index: 0= healthy roots, 3== dead roots. The effect of disinfectants was tested on cucumber. Treatment Disease index, 0-3 Efficiency % Trial 1 Trial 2 Trial 3 Trial 4 Mean Healthy control Water 0.56 a 0.28 a 0a 0a 1.50 b 0.92 b 2.56 c 3.00 c Formaline lobac P 0.24 a 0.56 a 0,11 a 0.22 a 96 1.43 b 0.56 a 2.34 c 1.22 b 34 Ipasept 1.56 b Menno-Ter-forte NaOCl 0.45 a 0.61 a 0.67 a 2.22 c 0.33 a 83 1.77 b 0.45 a 0.94 a 36 Taloset 1.24 b 0.28 a 0.89 a 67 Virkon S (2 %) 0.22 a 0.56 a 1.33 b 0.44 a 76 F-values 4.72** 7.6B*** 31.5*** 24.75*** Values in columns marked with the same letter do not differ at P=0.05. ** =P 0.01, ***=P 0.001 Sanisept and Virkon S (1 %) were weakly effect- ive against Pythium sp. (Table 7). Phomopsis sclerotioides in the peat debris on the surface of plastic pots was eradicated by formaline in the greenhouse trial. Menno-Ter-forte and Virkon S were moderately effective against the fungus. The effect of lobac P and NaOCl varied greatly in the different trials. They performed poorly in trials where the seedlings had been grown until fruit production (Table 8). The most effective disinfectants against V. dahliae in peat were form- aline, lobac P, NaOCl and Virkon S. Taloset was the least effective (Table 9). P. sclerotioides was effectively eradicated from sand substrate by formaline and NaOCl. Also Menno-Ter-forte was moderately effective. The least effective disinfectants against P. sclerotioides in sand were Virkon S and Taloset (Table 10). 184 Agric. Sei. Finl. 2 (1993) Table 9. The effect of disinfection on Verticillium dahliae in peat debris. Trials 1 and 2 lasted 6 weeks, trials 3 and 4 until fruit production. Results are based on laboratory cultures from the base pieces of cucumber seedlings. The effect of disinfectants was tested on cucumber. Treatment Healthy plants % Efficiency % Trial 1 Trial 2 Trial 3 Trial 4 Mean Healthy control Water 100.0 a 61.1 ab 91.7a 35.2 b 100,0 a 66.7 b 95.4 a 10.4 b Desinfektol EL Formaline 77.8 a 88.9 ab 100.0 a 55.6 b 92.6 a 85.2 a 83.3 ab 83.6 a 82 S3lobac P Ipasept 91.7 ab 73.2 a 88.9 ab Menno-Ter-forte NaOCI 77.8 ab 88.9 ab 66.7 ab 100.0 a 86.1 a 94.5 a 58.4 ab 75.5 a 67 SI 2S S4 95.4 a 86.1 ab Taloset 88.0 a 77.8 ab 0b Virkon S (2 %) 77.8 a 91.7 ab 82.9 a F-values 3.17* B.69*** 3.08* 9.75*** Values in columns marked with the same letter do not differ at P=0.05. * = P 0.05, ***=p 0.001 Table 10.The effect of disinfection on Phomopsis sclerotioides in sand substrate. Disease index: 0= healthy roots, 3= dead roots. The effect of disinfectants was tested on cucumber. Treatment Disease index, 0-3 Efficiency % Trial 1 Trial 2 Trial } Mean Mean Oa Oa Oa 0 2.40 c 2.00 c 2.00 b 2.13 1.00b 0.53 ab 0.77 0.20 a 0.67 ab 0.13 a 0.33 85 0.40 a 0.89 b 0.80 b 0.70 67 0.40 a 0.78 ab 0.40 a 0.53 75 0.40 a 0.22 ab 0.07 a 0.23 89 0.20 a 1.22 be 1.27b 0.90 58 0.80 b 1.33 be 1.34b 1.16 46 Healthy control Water Desinfektol EL Formaline lobac P Menno-Ter- forte NaOCI Taloset Virkon S (2 %) F-values 18.64*** 11.09*** 14.04*** Values in columns marked with the same letter donot differ at P=0.05. ***= PO.OOI The most effective preparations for disinfection of sand substrate from V. dahliae were formaline and NaOCI. lobac P was moderately effective. The least effective disinfectants were Taloset, Virkon S and Menno-Ter-forte. Desinfektol EL was equal to formaline in the first trial but ineffective in the second (Fig. 1). Discussion The laboratory trials showed that all disinfectants were effective against Pythium sp. in peat at 10min treatment time. In the greenhouse trials trying to disinfect plastic pots and washing suspension from Pythium sp., only Ipasept, Sanisept and Virkon S 185 Agric. Sei. Fin!. 2 (1993) (1%) were ineffective. The results are in accord- ance with the laboratory results of Baandrup (1983) and Koponen et al. (1992). In the laboratory trials, Didymella bryoniae was easily eradicated at 10 min treatment time from peal debris. Only lobac P was not effective against D. bryoniae because it was used at a concentration of 1 %. Formaline, Menno-Ter-forte, lobac P and Virkon S eradicated the fungus completely also from the surface of the plastic pots. According to Koponen et al. (1992), too, Menno-Ter-forte and NaOCI have yielded goodresult on plastic surfaces against D. bryoniae. This fungus has been effect- ively disinfested from wood surface and paper by formaline and Virkon S, respectively, (Sundheim 1991). In agar tests carried out by Johansson (1985), Korsolin (1%) and Menno-Ter-forte (0.5%) did not prevent the growth ofD. bryoniae at 1 min treatment time. Also in this study Korsolin was ineffective against D. bryoniae on plastic surface. In greenhouse trials only formaline was effective against Phomopsis sclerotioides mixed in peat. Menno-Ter-forte and Virkon S were moderately effective. NaOCI, in addition to formaline, was ef- fective against the fungus mixed in sand.However, Sundheim (1989) has reported that formaline (as fumes or sprays) was not effective against P. scle- rotioides in greenhouse experiment. In agar tests carried out in Sweden, Korsolin (1 %) and Menno- Ter-forte (0.5%) did not inhibit the growth of P. sclerotioides after one minute influence time (JO- HANSSON 1985). According to Sundheim (1989), only formaline was effective against P. sclerotioi- des on woodpieces in laboratory test. According to Sundheim (1991), Menno-Ter-forte was effective against P. sclerotioides in the paper test and Virkon S (1%) was ineffective. According to Koponen et al. (1992), many disinfectants (e.g. Menno-Ter- forte, NaOCI, Virkon S) needat least 60 min expos- ure time against P. sclerotioides to reach over 95 % effect in laboratory circumstances. The laboratory tests showed that only formaline was effective against V. dahliae in peat debris, lobacP, Korsolin and NaOCI eradicated the fungus completely from the surface of plastic pots. Ac- cording to Brielmaier (1985), Menno-Ter-forte has been effective against V. dahliae after 10 min influence time in a laboratory experiment, but in this study Menno-Ter-forte gave 92 % effect after 60 min on plastic surface. According to Koponen et al. (1992), Desinfectol EL, Menno-Ter-forte and NaOCI were effective against V. dahliae on syn- thetic cloth and plastic surface after 60 min influ- ence time in a laboratory test. In greenhouse trials formaline, lobac P, NaOCI and Virkon S were effective against V. dahliae in peat debris. Formaline and NaOCI were the most effective against the fungus in sand. The effect of lobac P and Desinfectol EL varied in different trials. Menno-Ter-forteand Virkon S were ineffect- ive against V. dahliae. In the greenhouse trials the effect of disinfectants varied in different trials. None of the disinfectants eradicated V. dahliae to- tally from peat debris. The most effective disinfect- ants against V. dahliae in peat debris were form- aline, lobac P, NaOCI and Virkon S. V. dahliae in sand substrate were eradicated most effectively by formaline and NaOCI. The effect of lobac P and Desinfectol EL varied in different trials. The results show that all the tested disinfectants Fig. 1. The effect of disinfection on Verticillium dahliae in sand substrate. Bars marked with the same letter do not differ significantly at P=0.05. 186 Agric. Sd. Fint. 2 (1993) are effective against Pythium sp. and Didymella bryo- niae. The effect of Ipasept, Sanisept and Korsolin varied. Virkon S should be used at concentrations of at least 2 %. Formaline is the most effective against Phomopsis sclerotioides and Verticillium dahliae. Although a treatment time of 10or 15 min was sufficient for most disinfectants to kill the fungi in the laboratory, a disinfection time of at least 60 min is recommended in practice. References Baandrup, M. 1983. Desinfektionsmidler. Specialrapport vid Köpenhamns universitet (Ref. Johansson 1985). Booth, C. 1971. Methods in microbiology. 795 p. Vol 4. Academic Press, London. Bouhot, D. 1975a. Recherches sur 1’ écologie des cham- pignons parasites dans le sol. V Une teenique sélective d’estimation du potentiel infeetieux des sois, terreaux et substrates infestés par Pythium sp., études qualitatives. Ann. Phytopath. 7: 9-18. 1975b. Recherches sur 1’ écologie deschampignons para- sites dans le sol. VIII Quantification de la teenique d’es- timation du potentiel infeetieux des sois, terreaux et sub- strates, infestés par Pythium sp. Ann. Phytopath. 7; 147- 154. Brielmaier, U. 1985. Wirkung von Desinfektionsmitteln auf pilzliche Krankheitserreger, die im Zierpflanzenbau von Bedeutung sind. Meded. Fac. Landbouww. Rijksuniv. Gent 50/3b: 1235-1242. Domsch, K. H., Gams, W. & Anderson, T.-H. 1980. Com- pendium of soil fungi. Vol. 1. Academic Press, London. 859 p. Fletcher, J. T. 1984. Diseases of greenhouse plants. 351 p. Longman, London. Johansson, A.-K. 1985. Löpande desinfektion i växthus av Xanthomonas pelargonii och X. begoniae. Disinfektion in greenhouses ofXanthomonas pelargonii and X. bego- niae. Institutionen för växt- och skogsskydd. (Sveriges Lantbr. Univ.) Examensarbeten 1985 (5) Uppsala. 67 p. Koponen, H., Avikainen, H. & Tahvonen, R. 1992. The effect of disinfectants on fungi in pure culture and on different surface materials. Agric Sci. Finl. 1:587-596. —, Avikainen, H. & Tahvonen, R. 1993. The effect of disinfectants on fungal diseases of potato and vegetables. Agric. Sci. Finl. 2: 169-177. Linnasalmi, A. 1955. Maan desinfiointi. Puutarhaviljelijäin liiton julkaisuja no. 111. Helsinki. 46 p. Murman, T. 1992. Kasvihuonekurkun viljely. Kauppapuu- tarhaliitto. Helsinki. 139 p. Sundheim. L. 1989. Desinfeksjonsmiddel mot soppar. Akt. Stat. Fagtj. Landbr. 3: 89-95. 1991. Reingering og desinfeksjon mot sjukdomar i veksthus. Plantevem i veksthus. Etterutdanninngskurs ar- rangert av statens fagtjeneste for landbruket 5. februar 1991. Mimeogr 5 p. Tahvonen, R. 1987. Lehtihometta ja lakastumista, kurkun kaksi uutta tautia. Koetoiminta jakäytäntö 44: 29. Manuscript received July 1992 Hanna Avikainen Risto Tahvonen Agricultural Research Centre of Finland Institute of Plant Protection FIN-31600 Jokioinen, Finland Hilkka Koponen Department of Plant Biology P.0.80x 28 FIN-00014 University of Helsinki, Finland 187 Agric. Sei. Finl. 2 (1993) SELOSTUS Desinfiointiaineiden teho kurkun sienitauteihin Hanna Avikainen, Hilkka Koponen jaRisto Tahvonen Maatalouden tutkimuskeskus ja Helsingin yliopisto Kymmenen desinfiointiaineen tehoa kurkun Didymella bryo- niae-, Pythium sp.-, Phomopsis sclerotioides- ja Verticillium dahliae- tauteja vastaan testattiin laboratorio ja kasvihuone- olosuhteissa vuosina 1988-1990.Tutkittavat valmisteet olivat Desinfektol EL (etanoli), formaliini (formaldehydi), lobac P (jodi), Ipasept, Menno-Ter-forte ja Sanisept jaTaloset (kvar- taarisiaammoniumyhdisteitä), Korsolin (glutaraldehydi), nat- riumhypokloridi (aktiivinen kloori) ja Virkon S (kaliumpe- roksisulfaatti). Laboratoriotesteissä testattiin valmisteiden suositeltujen käyttöväkevyyksien ja niistä tehtyjen laimennosten tehoa tur- peessa tai kasvijätteissä oleviin taudinaiheuttajiin. Lisäksi tut- kittiin käsittelyajan vaikutusta valmisteiden tehoon. Kasvi- huonetesteissä kasvatettiin kurkun taimia sienillä infektoidul- la turpeella liatuissa, desinfioiduissa muoviruukuissa. Val- misteiden tehoa testattiin myös Phomopsis- ja Verticillium sienillä infektoidun hiekka-alustan desinfioinnissa. Pythium- sienen aiheuttamaan kurkuntaimipolte-ja tyvitau- tiin tehosivat hyvin formaliini, lobac P, NaOCl, Korsolin ja Menno-Ter-forte. Heikkoja valmisteita olivat Ipasept, Sani- sept ja Virkon S (1%). Formaliini oli tehokkain kurkunmusta- juurimädän (Phomopsis sclerotioides) desinfioinnissa. Hiek- ka-alustalla oleva sieni voitiin hävittää myös NaOCklla. Ver- ticillium-sicncn aiheuttama kurkunlakastumistauti torjuttiin parhaiten formaliinilla, lobac P:llä, NaOCklla ja Virkon S:llä. Hiekan joukossa olevaan taudinaiheuttajaan tehosivat forma- liini ja NaOCl. Didymella bryoniae oli herkkä useimmille tutkituille desinfiointiaineille. Desinfiointiajaksi suositellaan vähintään tunnin käsittely- aikaa, vaikka lyhyempikin aika laboratoriotesteissä saattoi antaa hyvän tuloksen. 188 Agric. Sei. Finl. 2 (1993)