Competitive saprophytic ability (CSA) for pathogenic fungi of carnation, gerbera and marigold was studied using Cambridge methods. R. solani (carnation), F. oxysporum (gerbera) and F. moniliforme and F. oxvsporum (marigold) have high efficiency of CSA. Therefore, they were considered as vigorous competitive saprophytes. Furthermore, the same fungi of carnation and gerbera have also high degrees of tolerance to antibiotics produced by soil microorganisms and spore-forming bacteria. In contrast. F. oxysporum f.sp. dianthi (carnation), Phytophthora sp. (gerbera) and Phytophthora sp. (marigold) have low degrees of CSA and tolerance to antibiotics of soil microorganisms. Vitavax/Thiram was found to be an effective fungicide against F. oxysporum f.sp. dianthi and R. solani', the pathogenic fungi of carnation, followed by Topsin-M and Rizolex-T, respectively. However, cuttings were dipped in each fungicide suspension (509 ppm) for 15 minutes, directly before planting in infested soil. On the other hand, Topsin-M followed by Vitavax/Thiram as seed treatment (3g/kg seed) gave enough control to damping-off infection on marigold, under greenhouse conditions, where soil was infested with F. oxysporum or F. moniliforme. While, Vitavax/Thiram was superior in controlling the disease in field, followed by Monceren-Combi. To determine efficacy of biological control against diseases of carnation and marigold, Plant Guard (Trichoderma harzianum, 30xl06 cfu/ntl) and Rhizo-N (Bacillus subtilis, 30xl06 cfii/g) were used. Marigold seeds were dipped in Plant Guard (4 ml/L water) for 12 hours before planting, while Rhizo-N was used as seed dresser (4 g/kg seeds). The same rates of each biocide were used as soil drench in case of carnation. Results of these experiments indicated that they were effective treatments in decreasing the diseases incidence. Plant Guard was superior than Rhizo- N with the diseases of marigold. |
