No abstract

Dracaena sanderiana, of the family Liliaceae, is among the ornamental plants most frequently imported into Egypt. Typical anthracnose symptoms were observed on the stems of imported D. sanderiana samples. The pathogen was isolated, demonstrated to be pathogenic based on Koch's rule and identified as Colletotrichum dracaenophilum. The optimum temperature for its growth ranges from 25 to 30 °C, maintained for 8 days. Kemazed 50% wettable powder (WP) was the most effective fungicide against the pathogen, as no fungal growth was observed over 100 ppm. The biocontrol agents Trichoderma harzianum and Trichoderma viride followed by Bacillus subtilis and Bacillus pumilus caused the highest reduction in fungal growth. To the best of our knowledge, this report describes the first time that this pathogen was observed on D. sanderiana in Egypt.

No abstract

The effect of soil-applied Allium crop products on the Stromatinia cepivora viability and the incidence of white rot in subsequent onion and garlic crops were evaluated in this work. The tested products were onion powder, garlic powder, onion oil, garlic oil and Allium waste (onion and garlic) that are described as sclerotial germination stimulants. Under in vitro conditions, data revealed that more than 80% of the sclerotia died in the soil treated with sclerotial germination stimulants. Under greenhouse conditions, soil-artificially infested with sclerotia of S. cepivora and treated with sclerotial germination stimulants for 6-months before cultivation, significantly reduced the incidence of white rot on onion and garlic. Onion oil, garlic oil and Allium waste were the most effective treatments, decreasing disease incidence by 78.6% in onion and 80.0% in garlic. Under field conditions, sclerotial germination stimulants were incorporated into the soil in commercial fields naturally infested with S. cepivora. Two fields were chosen based on differential sclerotial density. Within 6 months after treatment, more than 70% of the sclerotia died in the plots treated with sclerotial germination stimulants. In subsequent onion and garlic crops planted approximately one year after soil treatment, sclerotial germination stimulants were more effective than the control in reducing white rot symptoms coupled with low inoculum density (45.9 sclerotia/kg of soil). Reduction of white rot disease was accompanied by increased of growth and bulbs yield of onion and garlic plants. Despite the efficacy of sclerotial germination stimulants to reduce populations of viable sclerotia in soil with a high inoculum density (594.7 sclerotia/kg of soil), the pathogen caused substantial white rot and yield losses in subsequent onion and garlic crops planted approximately one year after soil treatment.

Background: White rot, a garlic disease caused by the soil-borne fungus Stromatinia cepivora (Berk.) Whetzel, is a serious problem of garlic productions in Egypt. This study examines the potential of controlling the disease biologically by using three Trichoderma species, i.e., Trichoderma harzianum, Trichoderma koningii, and Trichoderma virens employed either alone or in combination. Results:In in vitro assays, three Trichoderma species, i.e., Trichoderma harzianum, Trichoderma koningii, and Trichoderma virens and tebuconazole, were compared for their ability to suppress S. cepivora isolate (Sc8). In greenhouse experiments, the chemical treatment was the most effective, with the lowest incidence of garlic white rot compared with the control. The antagonistic fungi tested either individually or in combination significantly reduced the incidence of white rot on garlic. In general, dual and triple combinations of the fungal isolates were more effective than these isolates used individually. The combination of the three Trichoderma species was the most effective treatment, decreasing disease incidence by 50.0% in 2016/2017 season and 40.0% in 2017/2018 season, respectively. The three Trichoderma species employed alone or in combinations and tebuconazole were evaluated under low and high disease pressures in field trials to determine which situation (s) provided the best control of garlic white rot. Under low (40 sclerotia/kg of soil) and high (600 sclerotia/kg of soil) inoculum density, the standard fungicide programme (dipping of garlic cloves in tebuconazole (1 ml of Folicur 25% l −1 of water) plus spraying garlic stem bases with the same concentration of tebuconazole) gave statistically significant disease control, decreasing disease incidence by 67.7 and 29.4% in 2016/2017 season and 72.6 and 31. 1% in 2017/2018 season, respectively. Under low disease pressure, significant control, equal to the fungicide treatment, was achieved with the trip combination of three Trichoderma species. However, Trichoderma species employed alone gave insignificant control of garlic white rot under high disease pressure. The triple combination of three Trichoderma species decreasing disease incidence by 65.6 and 15.5% in 2016/2017 season and 74.2 and 18.6% during 2017/2018 season, under low and high inoculum density, respectively. The activities of defense enzymes, i.e., peroxidase, polyphenoloxidase, and chitinase due to application of Trichoderma species, were enhanced in garlic plants either grown under low or high disease pressures. Reduction of white rot disease incidence was accompanied by increased growth parameters and bulbs yield of garlic plants grown under field conditions. Conclusions: These results indicated that the performance of three Trichoderma species may be influenced as much by the absolute disease pressure. It was concluded that, at the low disease pressure site, the low level of inoculum and disease incidence enabled three Trichoderma species to bring about disease control.