The effect of disinfectants on fungal diseases of potato and vegetables Hilkka Koponen, Hanna Avikainen and Risto Tahvonen Koponen, H., Avikainen, H. & Tahvonen, R. 1993. The effect of disinfectants on fungal diseases of potato and vegetables. Agric. Sci. Finl. 2: 169-177. (Dept. PI.Biol, P.0.80x 28, FIN-00014 University of Helsinki, Finland and Agric. Res. Centre of Finland, Inst. PI. Prot., FIN-31600 Jokioinen, Finland.) Treatments of one and ten minutes were too short for all disinfectants against fungi in peat and plant debris. The best effect was achieved with a treatment of 90 min. Sodium hypochlorite (NaOCl) was the most effective and Korsolin and Virkon S were the least effective in the control of Fusarium culmorum and F. oxysporum. Virkon S (2%) was the most effective against Mycocentrospora acerina and Phoma foveata. Soaking for 15 min and 60 min in a disinfection suspension eradicated Botrytis cinerea and P. foveata totally from the contaminated plastic pots. Fusarium spp. were the most difficult fungi to disinfect and these were best controlled with formaline, lobac P, Menno-Ter-forte and sodium hypochlorite. lobac P, formaline, Menno-Ter-forte, Taloset and Virkon S were the most effective disinfectants against club rot (Plasmodiophora hrassicae ).Washing under running water was not sufficient to eradicate club rot. Against Rhizoctonia -induced damping- off of cauliflower the most effective disinfectants were formaline and Virkon S. Key words: Botrytis cinerea, disinfection, Fusarium culmorum, F. oxysporum, Myco- centrospora acerina, Phoma foveata, Plasmodiophora hrassicae, Rhizoctonia solani Introduction Many plant diseases, which cause a decrease of yield and yield quality, survive on plant debris, growth substrates, mull debris, and greenhouse and storage structures for long periods. Therefore it is essential to use disinfectants to prevent the spread of diseases by those routes. Disinfection of soil substrate is not at present topical, because new peat or other currently used substrates are free of dis- eases. Grey mould (Botrytis cinerea) is a common dis- ease in vegetables and ornamental plants grown in greenhouses as well as in vegetable storages (Heinze 1974, Dennis 1983). Fusarium spp. are also commonly encountered in vegetables. They cause Fusarium rot (Fusarium avenaceum and F. solani var. coeruleum) of potato (SEPPÄNEN 1983), wilt disease (Fusarium oxysporum) of tomato and cucumber, as well as damping-off and foot rot (F. culmorum, F. avenaceum). Phoma spp. cause damping-off, stem rot and various leaf spot diseases in greenhouses as well as Phoma rot (Phoma fo- veata) of potato. Club rot (Plasmodiophora hrassi- cae) and damping-off (Rhizoctonia solani) are a major problem in cabbage cultivation, as soil-bome diseases also in seedling cultivation (Heinze 1974). Liquorice rot (Mycocentrospora acerina) has be- come a common disease ofcarrots in storage (Den- nis 1983). In order to prevent the spread of pathogens on a farm and from one farm to another, greenhouses. 169 Agric. Sei. Fin!. 2 (1993) https://www.c-info.fi/en/info/?token=5Ubxle4fjCoEeiu0.-AP-r1G6WkCe6ZacWJN7aA.bYvduDogMv0mP6Xyv140uj3akReuLEUyCUpjpxfEbpoLUmQJahZTtkKCIfSfldLu-WHMchvnX9JeR4cvQ3OZCanxKSmTnHiV9DstyAEPbbO5XSKUKv6cNoobEzZiwwT8a14D43h3VhBOl_Jjeif8PRS26V-vgyH6edhHxjRrLC6Qf2P-i9M5Ghk0szRabjvMUJuc9-2_CVjRkAGjK0XR-YOYwiGX8ZqJopnEKgBJuAu7QUnrK3fHXB_spRnN7MpZ92T6e9zp6uqlno0g_aEsWqLZZfYGcseXuCGX3zRxwpoxJLax0bKnunk seed storages, machines and tools must be disin- fected. There are several disinfectants on the mar- ket, but little is known about their applicability in plant production against important and common diseases. In 1988-1990, studies were conducted to determine the effect of disinfectants against fungal diseases of vegetables and potato. Material and methods The effect of nine disinfectants (Table 1) in the control of potato and vegetable diseases was tested at the Institute of Plant Protection of the Agricul- tural Research Centre. Mostly the concentrations recommended by the manufacturers were used in the trials. The disinfectants were diluted in water. The test fungi used were Botrytis cinerea, Fusa- rium culmorum, F. oxysporum, Mycocentrospora acerina, Phoma foveata, Plasmodiophora hrassi- cae and Rhizoctonia solani. The names of the fungi are mainly according to Domsch et al. (1980). The fungal isolates included in the study were obtained from the collections of the Institute ofPlant Protec- tionof the Agricultural Research Centre. The fungi were cultivated on different media depending on the fungus (Table 2). The formulas for culture mediaof fungi are presented in Booth (1971). The results were tested using the analysis of variance, and significances with Tukey’s test. The effect of disinfectants on the pathogens in peat and plant debris The effect of disinfectants on the pathogens in peat and plant debris was investigated in laboratory trials. The inoculated peat was obtained by mixing one Petri dish culture of fungus ( F. culmorum and F. oxysporum) and 100 ml of water in one litre of peat. The recommended concentrations (N) of dis- infectants and a lower concentration(10 1 N) were used. Inoculated peat, 1.0 and 0.1 g, was mixed in 11 ofdisinfection suspension. The preparation was allowed to act for 1,10and 100 min. Thereafter the suspension was filtered. The filter paper was Table 1. The disinfectants, their active ingredients and con centrations recommended by the manufacturers. Disinfectant Active ingredient, % Recommended concentration, % Formaline Formaldehyde, 37 5.0 lobac P lodine, 1.8 Ipasept Quaternary ammo- 2.0 nium compounds, 2.8 Korsolin Glutaraldehyde, 10 Menno-Ter-forte Quaternary ammo- 1.0 nium compounds, 32.5 Sanisept Quaternary ammo- 2.0 nium compounds, 2.5 Sodium hypochlorite Active chlorine, 10 (NaOCl) Taloset Quaternary ammo- 2.0 nium compounds, 3.5 Virkon S Potassium peroxysul- 1.0 phate, 60 Table 2. The growth media used in the fungal cultures. Fungus Growth medium Botrytis cinerea Com meal agar (Difco) + 100ppm streptomycin sulphate Fusarium culmorum Nash and Snyder PCNB medium F. oxysporum Nash and Snyder PCNB medium Mycocentrospora Com meal agar (Difco) + 100ppm acerina streptomycin sulphatestreptomycin sulphate Phoma foveata Malt extract agar (Difco) Corn meal agar (Difco) + 100ppm streptomycin sulphate Rhizoctonia solani Rhizoctonia agar (Ko and Hora 1971) washed with water (50 ml) and pieces of the filter paper were placed onto different agar plates de- pending on the test fungus (Table 2) (4 pieces/plate) to determine the viability of the fungi. The trial was made with three replicates. The effect ofdisinfectants on fungi was tested on polyethene surfaces. The inner surfaces of the plas- tic pots were scratched with sandpaper and con- taminated with fungus-peat inoculate. The inocu- late used was obtainedby mixing one plate of fun- gus (F. culmorum, F. oxysporum and R. solani) and 170 Agric. Sei. Fint. 2 (1993) 100 ml sterile water in one litre of peat, or by mixing five crushed pieces (4 cm long) of infected (B.cinerea, M. acerina and P. foveata) plant and 100 ml of sterile water in one litre of peat. The contaminated pots were allowed to dry for 1-2 days. Pieces (4x6 cm) cut from the plastic pots were soaked for 15 and 60 min in the disinfection solu- tion (100 ml). They were rinsed with water and cut into pieces of 0.5 cm onto different agar plates as above. The plates were evaluated after one and three weeks. The results were calculated as effi- ciency percentages, i.e. the proportion of healthy pieces on agar plates of all pieces. The effect of disinfectants on liquorice rot of carrot (M. acerina) and P. foveata of potato was investigated in a storage environment by inoculat- ing carrots and potatoes with disinfected peat con- taining the respective fungus. One decilitre (30 g) of peat inoculated with Mycocentrospora or Phorna and 2 1 of disinfection suspension were mixed. After 30 min (trial 1) or 60 min (trial 2) the peat was filtered and washed with water. The potatoes and carrots were washed and surface sterilized with 0.1% NaOCl solution for 2 min and thereafter washed with distilled water. Four holes (1 cm in diameter and 0.5 cm deep) were made in the pota- toes and three holes in the carrots using a cork borer. The holes were filled with inoculated and disinfected peat. The carrots were stored at +5°C and the potatoes at +lO-+l2°C for 4-6 weeks in the dark. Clean peat as well as water treated infected peat were used as controls. The trial was made with four replicates, ten treatments per replicate. The trial was repeated twice. The spread of the disease in the holes was evaluated in millimetres. The efficiency percentage of the disinfectants was calculated by comparing the treatments with the healthy controls and water treatments. The effect of disinfectants on club rot (Plasmodiophora brassicae) The club rot trials were carried out in the green- house. The containers (Vefi) were contaminated with Plasmodiophora brassicae infested soil (1.0 1 soil/1 1 water). The soil was taken from a club rot infected rape field. The containers were al- lowed to dry for one day before disinfection treat- ments. The treatments were: 1= control, no washing, no disinfection; 2=washing under running water; 3=washing under running water, disinfection for 60 min. After disinfection the containers were rinsed with water. On the next day about 130 rape seeds cv. ‘Kova’ were sown in fertilized peat (peat com- pound fertilizer 150 g and Dolomite lime 800 g/100 1 peat). Additional lightof 6000lux was given to the plants. The trial was made with three replicates. The seedlings were grown for about 6 weeks, until the end of flowering. The severity of the infection was determined as the proportion of infected seed- lings of all seedlings. The efficiency percentage was determined by comparing the effect of the preparation with the treatment ofno washing. The effect of disinfectants on damping-off (Rhizoctonia solani) The inoculated peat used in the trials was obtained by mixing one Petri dish culture of Rhizoctonia solani and 100 ml of water in one litre of peat. One decilitre of inoculated peat + one decilitre of fresh peat and two litres of disinfection suspension were mixed. The disinfectant was allowed to affect for 60 min. The suspension was filtered and the peat was rinsed with water twice. The fresh peat was used as a growth medium in plastic pots (1 1). A layer of 1 cm of disinfected inoculated peat was placed on fresh peat. Thirty-six seeds of cauli- flower cv. ‘Tanskalainen suuri’ were sown in the fresh peat and covered with a 0.5 cm layer of fresh peat. The number of replicates were five. The trial was repeated three times. The substrate, temperat- ure and light conditions were as above in the club rot trial. The conditions of seedlings were checked 20 days after sowing. The results were calculated as the proportion of healthy seedlings of all seed- lings. 171 Agric. Sei. Fin!. 2 (1993) 172 Table 3. The effect of concentration and disinfection time on Fusarium culmorum in peat debris. Disinfectants and concentra- tions (N): 1 = formaline (5 %), 2=lobac P (3 %), 3= Ipasept (2 %), 4 =Korsolin (1 %), 5 = Menno-Ter-forte (1 %), 6 =NaOCl (10%),7 = VirkonS(2%). Concen- Peat Disinfectant tration of g/1 1 Time 12 3 4 5 6 7 disinfectant disinfectant min Efficiency % Concen- 1 1 0 5) 93 5 95 93 0 tration (N) 10 8 83 93 18 98 100 68 100 93 93 93 5 95 100 100 0.1 1 0 80 95 8 100 93 0 10 93 83 93 45 100 100 0 100 93 95 95 25 100 100 75 10' 1 N 1 1 - 8 20 0 93 38 0 10 0 13 0 93 75 0 100 45 33 0 93 88 18 0.1 1 - 33 83 0 95 0 0 10 - 68 88 0 98 18 0 100 - 95 93 0 98 83 8 Table 4. The effect of concentration and disinfection time on Fusarium oxysporum 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 = NaOCl (10 %), 7 = Virkon S (2 %). Concen- Peat Disinfectant tration of g/1 1 Time 12 3 4 5 6 7 disinfectant disinfectant min Efficiency % Concen- 1 1 0 8 33 50 75 33 25 tration 10 17 30 55 50 93 75 0 (N) 100 83 93 83 88 88 100 68 0.1 1 0 70 80 0 95 93 0 10 100 83 88 50 100 100 8 100 100 93 93 50 100 100 100 10'N 11-008080 10 - 5 0 8 8 0 0 100 - 55 0 50 45 0 0 0.1 1 20 5 0 70 0 0 10 85 5 0 80 0 0 100 - 100 50 25 95 8 25 Results The effect ofdisinfectants on pathogens in peat and plant debris NaOCl was the most effective in the control of Fusarium culmorum when peat (1.0-0.1 g) was mixed in disinfectant. Also Menno-Ter-forte per- formed well. Korsolin was the weakest preparation (Table 3). NaOCl was effective also against F. oxysporum. The 100 min treatment time with Menno-Ter-forte, formaline and Virkon S was suf- ficient to disinfect the smallest amount of peat (0.1 g). Korsolin was the weakest preparation (Table Table 5. The effect of disinfection against fungi on the surface of plastic pots contaminated with fungus-peat mixture. Treatment Botrytis cinerea Fusarium culmorum Fusarium oxysporum Phoma foveala Rhizoclonia solani Minimum time min / efficiency % Water 60/83 60/0 60/25 60/8 60/42 Formaline lobac P 15/100 60/100 15/100 15/100 15/100 15/100 60/100 15/100 15/100 60/100 15/100 15/100 15/100 60/100 15/100 Ipasept Konsolin 15/100 60/75 60/100 60/100 60/100 60/17 60/92 60/58 Menno-Ter-forte NaOCl 15/100 15/100 15/100 15/100 15/100 15/100 60/100 15/100 Sanisept Taloset 15/100 60/50 60/92 60/100 15/100 60/100 15/100 Virkon S, 2 % 15/100 60/100 60/92 15/100 60/75 Table 6. The effect of disinfection on Mycocentrospora ac- erina in peat debris. The tests were carried out on carrots. Treatment Spread of the disease, mm Efficiency % Trial 1 Trial 2 Mean 30 min 60 min Healthy control 0 a 0.2 a Water 16.5 c 17.8 d Formaline 2.4 ab 21.0 d 32 lobacP 4.6 b 11.7 c 53 Ipasept 13.1 c Menno-Ter-forte 1.4 a 6.0 b 79 NaOCl 6.6 b 10.3 c 51 Taloset 7.8 b Virkon S 1 % 14.9 d VirkonS2% 0.3 a 3.8 ab 88 F-values 56.59*** 53.28*** Values in columns marked with the same letter do not differ at P=0.05. ***=Po.ool Table 7. The effect of disinfection on Phoma foveala in peat debris. The tests were carried out on potato tubers. Spread of the disease, mm Efficiency %Treatment Trial 1 Trial 2 Mean 30 rain 60 min Healthy control 0 a 0 a Water 19.2 d 15.3 c Formaline 1.9 ab 0.8 ab 92 lobacP 6.3 be 1.4ab 77 Ipasept - 2.8 b Menno-Ter-forte 5.4 b 0.3 a 84 NaOCl 4.7 b 0.3 a 86 Taloset 10.0 c Virkon S 1 % 0.7 ab VirkonS2% 0.6 a 0.2 a 98 F-values 58.71*** 107.44*** Values in columns marked with the same letter do not differ at P=0.05. ***=Po.ool 4). Lower than recommended concentrations were ineffective against F. culmorum and F. oxy- sporum. Soaking of contaminated (fungus-peat suspen- sion) plastic pots for 15 min in the disinfection suspension was sufficient to eradicate Botiytis cin- erea and P. foveala. Formaline, lobac P, Menno Ter-forte and NaOCl were the most effective disin- fectants against F. culmorum, F. oxysporum and Rhizoclonia solani. Ipasept, Korsolin and Sanisept were the weakest disinfectants on polyethene sur- faces contaminated with fungus-peat mixture (Table 5). in the trials where disinfected peat containing Mycocentrospora acerina was tested on the carrots, the most effective disinfectant was 2 % Virkon S. Menno-Ter-forte had a moderate effect. The effect of other disinfectants was weak (Table 6). In the potato trial on Phoma foveala Virkon S (2 %) was superior in efficacy to the other disinfectants. Ta- loset and Ipasept were the weakest preparations (Table 7). 173 Agric. Sei. Finl. 2 (1993) Table 8. The effect of disinfection on club rot (Plasmodiophora hrassicae) from contaminated plastic containers. The containers were washed with water before disinfection. Rape was used as test plant. Treatment Disease-% of seedlings Efficiency% Trial 1 Trial 2 Trial 3 Mean No washing, control 73.1 a 61.4 a 91.5 a 75.3 Water, control 5.8 b 7.1 b 46.2 b 19.7 73 Formaline 3.4 b 0.9 b 0.6 c 1.6 98 lobacP 3.2 b 0.3 b 0.3 c 1.3 98 Menno-Ter-forte I.lb Ob 0 c 0.4 99 NaOCI 3.4 b 2.2 b 0.8 c 2.0 98 Taloset - 1.0 c 1.0 VirkonS,2% 3.3 b 0.3 b 0.3 c 1.4 98 F-values 39.05*** 48.78*** 184.52*** Values in columns marked with the same letter do not differ at P=0.05. ***=Po.ool Table 9. The effect of disinfection on Rhizoclonia solani in peat debris. Cauliflower was used as test plant. Treatment Healthy seedlings, % Efficiency % Trial I Trial 2 Trial 3 Mean Healthy control Water, control Formaline 100.0a 36.8 ab 100.0a 31.0 ab 98.9 a 98.8 a 99.2 4.0 b 0b 13.6 100.0a 61.3 ab 24.2 b 95.4 a 98.5 98 lobac P Ipasept 57.0 ab 49.8 42 5.1 b 20.2 b 16.5 3 Menno-Ter- forte NaOCI 77.0 ab 31.5 ab 79.5 ab 100.0a 91.5a 72.4 ab 80.3 77 44.3 ab 41.3b 39.0 29 38Taloset 34.4 b 25.2 b 46.4 Virkon S, 2 % 96.0 a 81.4a 92.5 91 F-values 3.73* B.7l*** 7.B7*** Values in columns marked with the same letter do not differ at P=0.05. * = P 0.05, ***= PO.OOI The effect of disinfectants on club rot (Plasmodiophora brassicae) Washing under running water without a brush, the plastic pots were not sufficiently free from club rot. All tested disinfectants were effective against club rot, but none of them eradicated it totally. The differences between the preparations were not sig- nificant (Table 8). The effect of disinfectants on damping-off (Rhizoclonia solani) Formaline and Virkon S were the most effective against Rhizoclonia induced damping-off. Menno-Ter-forte also performed well. Ipasept, lobac P and NaOCI were the weakest disinfect- ants (Table 9). 174 Agric. Sd. Fint. 2 (1993) Discussion In the present trials, 100% effect against Fusarium oxysporum mixed in peat was achieved only with NaOCl (10 %) after 100 min exposure time. These results are opposite to those of BÖHMER (1983) who showed that NaOCl (1 %) had no effect on F.oxy- sporum. This is due to the higher concentration of NaOCl used in the present study. Menno-Ter-forte, Virkon S and formaline were also effective against the fungus in a small amount of peat (0.1 g/11 1 disinfectant). Also BÖHMER (1985) showed that a small amount of peat (15-30 g/1) does not decrease the effect of Menno-Ter-forte on F. oxysporum but a large amount (60 g/1) decreases the effect of Menno-Ter-forte. Under clean conditions Menno- Ter-forte (0.5 %) has been shown to inhibit the growth ofF. oxysporum conidia even after 5 and 10 min treatment time (Böhmer 1983, Brielmaier 1985) but this and other studies (Böhmer 1985) confirm that the peat in the disinfection solution decreases the effect ofMenno-Ter-forteand a treat- ment time of 60 min at least should be used. According to Baandrup (1983), 2 % Korsolin in- hibited the growth ofF. oxysporum, but we used 1 % Korsolin and it was too weak against F. oxy- sporum. In this study, lobac P did not inhibit totally the growth ofF. oxysporum and the effect of lobac P was decreased in the presence of peat. NaOCl was the most effective against F. cuI mo- rum mixed in peat after 10 min treatment time. Menno-Ter-forte was moderately effective against F. culmorum mixed in peat when used at the re- commended concentration. BRIELMAIER (1985), too, showed that Menno-Ter-forte prevents the ger- mination of conidia of F. culmorum under clean conditions. When using a treatment time of 100 min, only Korsolin was ineffective against F. cul- morum. Also this study showed that a treatment time of at least 60 min shouldbe used. According to BÅNG (1987a, b), formaline is ef- fective against Phoma foveata and F. solani, but lobac P is not. In the present trials, lobac P was a weak disinfectant against P. foveata mixed in peat, but formaline was effective against P. foveata. In this and other studies (Sundheim 1991), for- maline was effective against Rhizoctonia solani mixed in peat after a treatment of 60 min. Also Virkon S was effective against the fungus and it was equal to formaline in disinfecting R. solani from peat but in disinfecting plastic pots Virkon S was ineffective against R. solani. In the present trials, lobac P was very effective against R. solani in disinfecting plastic pots, but in disinfecting R. solani from peat it performed poorly. The results are partly affected by the fact that lobac P caused damage to the cauliflower seedlings, which were used as test plants. Damping-off of cauliflower could not always be distinguished from the phyto- toxicity injuries caused by lobac P. The use of cauliflower to indicate the efficacy of disinfectants is not the best choice because many disinfectants in peat cause phytotoxicity injuries to plants (Avikai- nen et al. 1993). F. oxysporum was effectively eradicated from plastic pots with formaline, lobac P, Menno-Ter- forte, Ipasept and NaOCl. Fifteen minutes exposure time was enough for formaline and Menno-Ter- forte, but lobac P, Ipasept and NaOCl needed 60 min. In these trials, Korsolin and Virkon S were effective against F. oxysporum although the effect was not perfect. In the present study, all the tested disinfectants were effective against Botrytis cinerea when plastic pot surfaces were contaminated with a fungus and peat mixture. A treatment time of 15 min was suffi- cient for all disinfectants exceptKorsolin. In this and other studies, formaline was effective against B. cinerea (Hortica 1985, JOHANSSON 1985, Sund- HEIM 1989, 1991). Menno-Ter-forte has proved effective against grey mold growing on pieces of paper or on synthetic cloth, but not on pieces of wood (Sundheim 1991, Koponen et al. 1992b). According to SUNDHEIM (1991), Virkon S (1 %) is not effective against grey mold, but this study showed that it is a very good compound in disinfect- ing plastic pots contaminated with fungus and peat. In disinfecting plastic pots all disinfectants were effective against P. foveata after a treatment of 60 min. According to BÅNG (1987a, b), formaline is effective against P. foveata. The result is in accord- ance with this study. In greenhouse trials imitating seedling produc- tion, 60 min treatment of plastic pots in disinfection 175 Agric. Sei. Finl. 2 (1993) suspension against Plasmodiophora hrassicae gave a good result although none of the disinfectants were capable of eradicating the fungus totally. Also in other studies Menno-Ter-forte (1.5 %) has been effective against P. hrassicae when plastic pots were soaked in disinfection solution for 12 h (Hadler 1988). Whereas only washing with water or spraying of the disinfectant on the surface to be disinfested was not sufficient to eradicate club rot (Hadler 1988). The present trials confirm the fact that dirt and organic material decrease the effect ofdisinfectants. The dirtier the surface to be cleaned, the longer disinfection time is needed. The disinfection time should always be at least 60 min. Although 15 min or less is sufficientin laboratory tests to eradicate the; pathogen, it is not necessarily sufficient in practice. Virkon S, lobac P and NaOCl are effective disin- fectants against many potato pathogens, e.g. Rhi- zoctonia solani, Phomafoveata and Fusarium spp. lobac P can be used also for bacterial ring rot of potato (Clavihacter michiganensis subsp. sepe- donicus) and black leg (Erwinia carotovora subsp. atroseptica) (Koponen et al. 1992a). lobac P, Menno-Ter-forte and Virkon S are good alternatives to those who want to avoid formaline in disinfection of plastic pots from Plasmodiophora hrassicae. Formaline and Virkon S are effective against R. solani when organic material is present, but plastic surfaces may be disinfected with lobac P, Menno- Ter-forte, NaOCl and formaline. References Avikainen, H., Koponen, H., Meinander, B. & Tahvonen, R 1993. The phytotoxicity of disinfectants and their effect at different temperatures, Agric. Sci. Finl. 2: Baandrup, M. 1983. Desinfektionsmidler. Specialrapport vid Köpenhamns universitet (Ref. Johansson 1985). Bäng, U. 1987a. Försök med desinfektionsmedel. Spor pota- tisodl. 5 (2); 32-34 1987b. Redovisning av försök med desinfektioin genom dimning i konstantrum vid Röbäcksdalen i september 1986. Mimeogr. 5 p. Böhmer, B. 1983. Untersuchungen zum Einsatz von Desin- fektionsmitteln im Zierpflanzenbau. Gesunde Pfl. 35: 189-197. 1985. Nicht alle Mittel wirken unter Schmutzbelastung, Gärtnerbör. und Gartenw. 85: 836-838. Booth, C. 1971. Methods in microbiology. Academic Press. London. Vol. 4. 795 p. Brielmaier, U. 1985. Wirkung von Desinfektionsmitteln auf pilzliche Krankheitserreger, die im Zierpflanzenbau von Bedeutung sind. Meded. Fac. Landbouww. Rijksuniv. Gent 50/3b: 1235-1242. Dennis, C. 1983. Post-harvest pathology of fruits and veget- ables. Academic Press. London. 264 p. Domsch, K. H., Gams, W. & Anderson, T.-H. 1980. Com- pendium of soil fungi. Academic Press. London. Vol. 1. 859 p. Hadler, C. 1988. Versuchbericht zur Priifung der Eignung von Menno-Ter-forte zur Desinfektion von Jungpflan- zenanzuchtgefassen. Mimeogr. 2 p. Heinze, K. 1974. Leitfaden der Schädlingsbekämpfung. Band 1. Schädlinge und Krankheiten im Gemiisebau. Wissenschaftliche Verlagsgesellschaft MBH. Stuttgart. 360 p. Hortica 1985. Kan formalin ersättäs? Hortica 2 (9); 23-25 Johansson, A.-K. 1985. Löpande desinfektion i växthus av Xanthomonas pelargonii och X. begoniae. Disinfektion in greenhouses of Xanthomonas pelargonii and X. bego- niae. Institutionen för växt- och skogsskydd. (Sveriges Lantbr. Univ.) Examensarbeten 1985 (5) Uppsala. 67 p. Ko, W.-H. & Hora, F. K., 1971. A selective medium for quantitative determination of Rhizoctonia solani in soil. Phytopathology61: 707-710. Koponen, H., Manninen, M., Harju, P., Avikainen, H. & Tahvonen, R. 1992a. The effect of disinfectants on Clavihacter michiganensis subsp. sepedonicus and Er- winia carotovora subsp. atroseptica on different surface materials. Agric. Sei. Finl.l: 597-602. Koponen, Avikainen, H. & Tahvonen, R, 1992b. The effect of disinfectants on fungi in pure culture and on different surface materials. Agric. Sci. Finl. 1:587-596. Seppänen,E. 1983. Fusariums of the potato in Finland VIII. Occurence of the pathogens causing potato dry rot and gangrene. Ann. Agric. Fenn. 22; 115-119. Sundheim, L. 1989. Desinfeksjonsmiddel mot soppar. Akt. Stat. Fagtj. Landbr. 3; 89-95. 1991. Reingering og desinfeksjon mot sjukdomar i veksthus. Plantevern i veksthus. Etterutdanninngskurs ar- ranger! av statens fagtjeneste for landbruket 1991. Mimeogr. 5 p. 176 Agric. Sei. Finl. 2(1993) Manuscript received July 1992 Hanna Avikainen Risto Tahvonen Hilkka Koponen Agricultural Research Centre of Finland Institute of Plant ProtectionDepartment of Plant Biology P.0.80x 28 FIN-31600 Jokioinen, Finland FIN-00014 University ofHelsinki, Finland SELOSTUS Desinfiointiaineiden teho perunan ja vihannesten sienitauteihin Hilkka Koponen, Hanna Avikainen ja Risto Tahvonen Helsingin yliopisto ja Maatalouden tutkimuskeskus Yhdeksän markkinoilla olevan desinfiointiaineen tehoa vi- hannesten ja perunan tauteja aiheuttaviin sieniin tutkittiin Kasvinsuojelun tutkimuslaitoksella vuosina 1988-1990. Tut- kittavat valmisteet olivat formaliini (formaldehydi), lobac P (jodi), Ipasept, Menno-Ter-forte ja Sanisept ja Taloset (kvar- taarisia ammoniumyhdisteitä), Korsolin (glutaraldehydi), nat- riumhypokloriitti (aktiivinen kloori) jaVirkon S (kaliumper- oksisulfaatti). Laboratoriotesteissä tutkittiin valmisteiden suositeltujen käyttöväkevyyksien tehoa turpeessa tai kasvijätteessä oleviin Bortrytis cinerea-, Fusarium culmorum-, Fusarium oxyspo- rum-, Mycocentrospora acerina- jaPhoma foveata- sieniin. Lisäksi testattiin käsitelyajan vaikutusta valmisteiden tehoon. Sienten elävyys testattiin agarmaljoilla. Porkkananmustamätä (M. acerina ) ja perunan Phoma-mätä (P. foveata) testattiin laittamalla saastutettu ja desinfioitu turve porkkanoihin ja perunoihin ja säilyttämällä juureksia varasto-olosuhteissa. Turve- jakasvijätteessä olevien taudinaiheuttajien desinfioin- tia muovipinnalta tutkittiin liottamalla liattuja muoviruukun paloja eri aikoja desinfiointiaineissa. Sienten elävyys testattiin agarmaljoilla. Yhden ja kymmenen minuutin vaikutusajat olivat kaikilla valmisteilla liian lyhyitä turpeessa ja kasvijätteissä oleviin sieniin. Paras teho saatiin 1,5 tunnin käsittelyllä. F. culmo- rum- jaF. oxysporum- sieniin paras teho oli natriumhypoklo- riitilla, huonoin Korsolinilla ja Virkon S:llä. M. acerina- sie- neen tehosi parhaiten Virkon S (2 %). Formaliini, natriumhy- pokloriitti, lobac Pja Taloset olivat teholtaan huonoja. Virkon S (2 %) tehosi parhaiten myös P. foveata- sieneen. Viidentoista minuutin ja turmin liotus desinfiointiaine- liuoksessapuhdisti liatut muoviruukut hyvin B. cinerea- ja P. foveata- sienistä. Fusarium spp.-sienet olivat vaikeimpia puh- distaa. Paras teho niihin oli Formaliini-, lobac P-, Menno-Ter- forte- ja natriumhypokloriitti- valmisteilla. Korsolin, Ipasept jaSanisept olivat teholtaan huonoja valmisteita. Desinfioinnin vaikutusta möhöjuureen (Plasmodiophora hrassicae) ja Rhizoctonia solani- taimipoltteeseen testattiin kasvihuoneessa taimikasvatuskokeissa. Möhöjuurella liattuja muovisia lokerikkoja liotettiin desinfiointiaine laimennoksissa yhden tunnin ajan. Lokerikoissa kasvatettiin rypsin taimia noin kuusi viikkoa. Taimista analysoitiin juurten tautisuus. Rhizoctonia solani taimipolte kokeessa testikasvina oli kuk- kakaali. Kaikki tutkitut desinfiointiaineet tehosivat hyvin mö- höjuureen. Huuhtelu juoksevalla vedellä ei riittänyt möhöjuu- ren puhdistamiseen. Kukkakaalin Rhizoctonia-taimipolttee- seen tehosivat parhaiten formaliini ja Virkon S. Huonoimpia valmisteita olivat Ipasept, lobac P ja natriumhypokloriitti. Desinfiointiaika tulisi olla vähintään tunti. Vaikka viisitois- ta minuuttia ja lyhyempikin aika riitti joidenkin taudinaiheut- tajien puhdistamiseen laboratoriokokeissa, se ei välttämättä riitä käytännön olosuhteissa. Porkkanavarastojen desinfiointiin soveltuvat parhaiten Virkon S(2 %)ja Menno-Ter-forte, perunavarastojen lobacP, Virkon S ja NaOCl. Möhöjuuren desinfiointiin soveltuvat hyvin lobac P, Menno-Ter-forte, Virkon S jaformaliini. Rhi- zoctoma-taimipoltteen saa parhaiten puhdistettua formaliini- jaVirkon S-valmisteilla. 177 Agric. Sei. Finl. 2 (1993)