Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: Ramsey Sealy x
Clear All Modify Search

Biological substrate amendments including SG-11, Subtilex, SoilGuard, ActinoIron, Companion, RootShield and BioYield were evaluated for their efficacy to control common soil-borne fungal and fungal-like pathogens when incorporated into the substrate at transplanting. The biological agents were incorporated into an 80% Sphagnum peat and 20% perlite substrate at the label recommended rates and four-to-six-leaf plugs of the test species were transplanted into the substrates. Substrates were either inoculated or uninoculated with a test pathogen. Pathogen-host combinations included Pythium ultimum on geranium (Pelargonium ×hortorum), Phytophthora nicotianae and Pythium aphanidermatum on vinca (Catharanthus roseus), and Theilaviopsis basicoli on pansy (Viola ×wittrockiana). The incidence of disease development, plant mortality and root fresh weights did not differ among the biological agents and the inoculated controls. Therefore, under the conditions of this study, the biological agents did not provide significant disease suppression. Pansy and vinca plants grown in uninoculated substrates amended with Subtilex had significantly higher shoot dry weights than those grown in unamended substrates. Pansy, vinca and tomato plants grown in uninoculated substrates amended with SG-11 had significantly higher shoot dry weights than those grown in unamended substrates.

Free access

Growth of Pythium aphanidermatum, Pythium ultimum, Pythium irregulare, Phytophthora nicoctianae, Phytophthora cinnomomi, Fusarium oxysporum, Rhizoctonia solani and Thielaviopsis basicoli was inhibited in vitro when grown in a clarified V-8 nutrient solution containing 10% garlic extract. After exposure to 10% garlic extract for 3 days, all fungi and fungal-like organisms failed to grow after being washed and transferred to fresh cornmeal agar nutrient medium without garlic extract. When Sphagnum peat was inoculated with P. aphanidermatum and drenched with solutions containing varying concentrations of garlic extract, a single drench of 35% garlic extract or two drenches of 15% garlic extract were required to rid the substrate of viable P. aphanidermatum. In sand, a single application of 25% garlic extract or two applications of 10% garlic extract were required to rid the sand of viable P. aphanidermatum Thus, Sphagnum peat appeared to partially inactivate the components in garlic and did so to a greater extent than sand. Therefore, efficacy of garlic extract as a soil drench fungicide will be affected by the type of substrate or soil to which the garlic extract is applied.

Free access

Pythium aphanidermatum, Pythium irregulare, Pythium ultimum, Phytophthora cinnomomi, Phytophthora nicotianae, Rhizoctonia solani, Fusarium oxysporum, and Thielaviopsis basicoli grew and eventually covered petri plates containing a nutrient solution alone, but they failed to grow in nutrient solutions containing 10% or higher levels of garlic extract or a fungicide control. When plugs containing the fungal organisms exposed to 10% garlic (Allium sativum) extract solution for 48 h were washed and transferred to fresh cornmeal agar (CMA) growth medium, only F. oxysporum displayed growth. However, growth of F. oxysporum was limited to no greater than 2 mm from the original inoculum plug. After a single application of a solution containing at least 35% garlic extract or two applications containing 25%, viable P. aphanidermatum could not be recovered from a peat-based root substrate. By contrast, after a single application of a solution containing 25% garlic extract or two applications of 10%, we were unable to recover viable P. aphanidermatum from a sand substrate. When peat treated with increasing concentrations of garlic extract was placed on CMA inoculated with P. aphanidermatum, the first visual sign of a zone of inhibition occurred for peat saturated with 30% garlic extract solution and the zone increased as the garlic extract concentration increased. By contrast, when sand treated with increasing concentrations of garlic extract was placed on CMA inoculated with P. aphanidermatum, the first visual sign of a zone of inhibition occurred when saturated with 10% garlic extract solution. Therefore, the garlic extract was found to be fungicidal against a broad range of soilborne fungal organisms, but the concentration required to kill the organisms varied depending on root substrate.

Full access

The effects of three light levels (1403, 806, and 462 μmol·s-1·m-2 on the severity of damping-off caused by Pythium myriotylum Drechsler in Amaranthus hybridus L. `Quelite' were tested. The observed mortality (33%, 69%, and 81%, respectively) decreased as light intensity increased. The reduction in plant growth and maturity in a shaded location is related to the observed increase in suspectibility to damping-off in such an environment.

Free access

Vinca (Catharanthus roseus) is a common annual bedding plant species that is susceptible to root and stem rot caused by Phytophthora nicotianae. The experimental design was a 6×2×1 factorial with a total of 12 treatment combinations that had five replications and was repeated twice. Vinca seeds were planted in the middle nine plugs of a 5×5 five-milliliter round plug tray filled with sphagnum peat (control) or peat amended with 2.1 kg/m3 calcitic lime, 5.9 and 7.3 kg/m3 potassium silicate alone and combined with 3.0 kg/m3 calcium sulfate. A peat control drenched with metalaxyl after inoculation was also included. After germination, when the seedlings had one true leaf, half of the treatments were inoculated with 500 cfu of Phytophthora nicotianae per plug cell while the other half remained uninoculated. The percentage of germination for the potassium silicate combined with calcium sulfate (KSCS) (79% and 78%) was similar to the control (86%) and the metalaxyl treatment (83%), whereas the potassium silicate alone had poorer germination (69% and 71%) and plant growth. The percentage of mortality for the KSCS treatment (6% and 14%) was similar to the metalaxyl treatment (9%) but was significantly less than the control (100%). The average dry shoot and root weights for the KSCS treatments (4.4 and 4.9 mg; 2.7 and 2.2 mg) were similar to the metalaxyl treatment (5.0 and 3.6 mg) and the uninoculated control (5.0 and 3.2 mg), but were higher than the potassium silicate treatment alone (2.1 and 1.6 mg; 0.7 and 0.6 mg).

Free access