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Powdery mildew (Podosphaera pannoso) is one of the most serious fungal diseases on both greenhouse and field grown roses. Improvement of disease resistance is a major selection aim for garden rose breeders. For rose cultivars, being mostly tetraptoid, it is complicated to develop molecular markers for resistance. Hence, a segregating diploid population was established from a cross between 'Yesterday', a commercial available rose variety susceptible to powdery mildew, and R. wichurana, a rose species with resistance to certain isolates of powdery mildew. A progeny of 94 seedlings was planted in the field. The segregation of powdery mildew resistance was studied in this population by means of a bioassay with two different monoconidial isolates of powdery mildew. Based on the response to these inoculations different groups were selected: a first group of genotypes was susceptible to both isolates, other groups were susceptible to one of both isolates and a last group was resistant to both tested isolates. The disease resistance inherits for both isolates in a quantitative way. A genetic map based on AFLP and SSR markers was established and will be used for QTL analysis of powdery mildew resistance.

Among downy mildews occurring on ornamentals in Poland the most dangerous are downy mildew of rose and downy mildew of German statice (Tartarian statice). Downy mildew of rose caused by Peronospora sparsa Berk. is a serious threat to commercial cultivation of cut roses, especially grown under plastic tunnels. Peronospora statices Lobik casual agent of German statice downy mildew can causes the total losses in the second year of statice cultivation more than 70%. Both pathogens are very difficult to control. Effectiveness of azoxystrobine, cymoxanil + famoxate, mancozeb, phosethyl aluminium, phosethyl aluminium + fenamidone, propamocarb in the control of P. sparsa and P. statices was presented. In the control of statice downy mildew none of tested compounds was able to control satisfactory the pathogen. Relatively the best results were obtained with mixture of fenamidone (88 microg/cm3) and phosethyl AL (1334 microg/cm3). In the control of rose downy mildew, the best results were obtained with phosethyl Al at concentration 1600 microg/cm3.

In the control of Sphaerotheca pannosa var. rosae on rose Tolylfluanide + tebuconazole (Folicur Multi 50 WG at concentration 0.1%) was used for spray 2 -times at 14-day-intervals or 4-times at 7-day-intervals. After 4 weeks of plants protection effectiveness of tested product was about 75%. In the control of Diplocarpon rosae, the product was applied when first disease symptoms appeared on rose shrubs. Application was repeated 5-times at 14-day-intervals or 9-times at 7-day-intervals. After 9 week-protection effectiveness of tested product was about 85% and depended on frequency of sprayings. In the control of Puccinia horiana on chrysanthemum, Tolylfluanide + tebuconazole was used as plant spray twice at 14-day-intervals or 4-times at 7-day-intervals. After 4 week-protection the product suppressed of new telia formation about 55%. Application of the product for willow rust (Melampsora epitea) control suppressed formation of new uredia about 86% and half of them were dried. In the control of pelargonium rust (Puccinia pelargonii-zonalis) the product was used as plant spray 4-times at 7-day-intervals. It suppressed formation of new uredia about 90% and 1/3 of them were dried. It was found that 1 or 7 days after rose spray, spores of D. rosae collected from leaf blades only in 6% germinated. Spores taken from nonspraying leaves germinated in 90%. In case of P. pelargonii-zonalis, after 1 or 7 days after spraying, spores collected from protected plants germinated at 3%, compared to 90% on untreated plants. Spores of B. cinerea, collected from protected plants germinated at about 10%, whereas on control leaves at 90%.

Chitosan, (Biochikol 020 PC) a potential elicitor of plant defence and also an active inhibitor of fungal growth was used in experiments. The compound was used at concentrations 0.01 to 0.2% as a plant spray for rose protection against Sphaerotheca pannosa var. rosae, Peronospora sparsa and Diplocarpon rosae, Oidium chrysanthemi and Puccinia horiana on chrysanthemum, against Melampsora epitea on willow. Myrothecium roridum on dieffenbachia and against Lophodermium spp on Scots pine. Effectiveness of this product, applied curatively 2-times at 7-day-intervals after appearance of rose powdery mildew symptoms on most of plant parts, was about 32%. When compound was applied just after the first disease symptoms appearance, after 2-week-protection its effectiveness was about 43-60%. After 4 weeks, effectiveness of chitosan (Biochikol 020 PC) increased and ranged from 67 to 77%. In the control of P. sparsa on rose shrubs, growing in plastic tunnel, chitosan at conc. 0.025% was applied 4 times at weekly intervals. Effectiveness of chitosan against this pathogen was over 72%, similar as standard fungicide. Increase of chitosan (Biochikol 020 PC) concentration resulted in decrease of its effectiveness. In case of D. rosae control, chitosan used 9 times at weekly intervals was applied after first disease symptoms. After 3-week-protection effectiveness of the compound varied from 18 to 60% according to used concentration. After 9 weeks of protection effectiveness of tested product ranged from 16 to 23% and was connected with used concentration. Increase of chitosan concentration resulted in better protection of rose shrubs. Effectiveness of chitosan (Biochikol 020 PC) used 4-times at conc. 0.01 to 0.05% as chrysanthemum spray in the control of Oidium chrysanthemi ranged from 69 to 79%, whereas against Puccinia horiana from 54-97%. Two-time-spraying of willow with rust symptoms (Melampsora epitea) with chitosan at conc. 01-0.04% caused decrease of disease severity from 26 to 47%. Additionally about 10 to 25% of uredinia were dried up. Chitosan (Biochikol 020 PC) applied for leaf spraying inhibited the development of Myrothecium leaf spot on dieffenbachia more than 85%. Curative application of the compound controlled Myrotecium leaf spot at about 40%. Chitosan efficacy was also tested against one-year-old Pinus sylvestris seedlings growing in field conditions. Plants were sprayed fortnightly 14-times (long programme) or 5-times (short programme) against Lophodermium spp. Observations made during next spring showed that effectiveness of chitosan (Biochikol 020 PC) was more than 50% (long programme) and below 50% (short programme).

The constant input of chemical fungicides against foliar diseases in glasshouse crops has instigated research on alternative control substances. Various salts have been mentioned in the literature and we have tested several bicarbonates, sulphates and phosphates against powdery mildew fungi in cucumber, tomato, sweet pepper and rose and against Bremia lactucae in lettuce. The experiments were run according to EPPO guidelines for efficacy in glasshouses of Applied Plant Research (PPO). Plants were sprayed weekly and disease and yield were assessed. In cucumber, NaHCO3, KHCO3, MgSO4 and MnSO4 all reduced powdery mildew significantly, with MnSO4 as the most effective agent. In tomato, MgSO4, MnSO4 and KH2PO4 all reduced powdery mildew by approx. 40% whereas NaHCO3 and KHCO3 gave approx. 95% control. In pepper, NaHCO3 controlled Leveillula taurica by 50-90% compared to the untreated control. In rose, the efficacy of KH2PO4, MnSO4, MgSO4, NaHCO3 and KHCO3 against powdery mildew differed between cultivars. In general, the bicarbonates were the most effective compounds. In lettuce, NaHCO3 reduced Bremia severity by 70 to 80%. The conclusion of this range of experiments is that especially bicarbonates can be a good alternative for control of foliar fungal diseases in glasshouse crops. The effective concentration is not causing any symptoms of phytotoxicity, provided that spraying is not done at high irradiation conditions. Bicarbonates have been submitted for the Dutch list of exceptions on the Pesticide Law.

In the control of grey mould (Botrytis cinerea) on rose petals all 15 tested fungicides used as a spray, suppressed very effectively development of necrosis. But the best results in suppression of necrosis development, more than 90% effectiveness gave: Amistar 250 SC (azoxystrobin), Bravo 500 SC (chlorothalonil), Discus 500 WG (kresoxim methyl), Euparen 50 WP (dichlofluanid) Euparen Multi 50 WG (tolyfluanid), Folpan 80 WG (folpet), Kaptan zaw. 50 WP (captan), Penncozeb 80 WP (mancozeb), Ronilan 50 WP (vinclozolin), Rovral Flo 255 SC (iprudione), Sumilex 500 SC (procymidone) and Teldor 500 SC (fenhexamid). When Dithane M-45 80 WP (mancozeb), Sarbrawit 530 SC (chlorothalonil + carbendazim) or Topsin M 70 WP (thiophanate methyl) were used, the diameter of spots was about 6-times smaller than on control flowers (about 84% effectiveness). All tested fungicides used for spraying of flower petals with abundant visible sporulation of B. cinerea were ineffective in the inhibition of spore germination. But when Petri dishes with potato-dextrose-agar were sprayed with tested fungicides and inoculated with spore suspension, Euparen 50 WP, Euparen Multi 50 WG, Folpan 80 WG, Kaptan zaw. 50 WP and Penncozeb 80 WP completely suppressed conidia germination.