Abstract
Pythium irregulare was isolated from roots and found to be pathogenic to 4 different hosts showing various disease syndromes in one southern California nursery. The hosts were Dizygotheca elegantissima Vignier & Guill., Brassaia actinophylla Endl. Ilex cornuta Lindl. & Paxt. cv. Rotunda and Nerium oleander Linn. cv. Petite Salmon. One isolate was more damaging on D. elegantissima growing at a mean temperature of 15.5°C than at a mean temperature of 23°C. A bioassay proved that P. irregulare was an inhabitant of the soil at the site of the nursery.
incidence of Pythium spp. in floriculture crops was reported in Pennsylvania in 2002 ( Moorman et al., 2002 ): P. irregulare and P. aphanidermatum were the most common species. In Michigan, it was found that P. irregulare , P. ultimum , and P
crops in the northeastern United States were used for this study, Pythium aphanidermatum (Edson) Fitzp., P. cryptoirregulare (Garzón, Yánez, and Moorman), and P. irregulare Buisman. Cultures were maintained on colonized water agar (WA) blocks in
; however, P. ultimum , P. aphanidermatum , and P. irregulare are isolated frequently from symptomatic plants in commercial production ( Del Castillo Múnera and Hausbeck, 2016 ; Moorman et al., 2002 ). Pythium species are ubiquitous in natural
Effect of garlic extract on soilborne fungal pathogens in an in vitro nutrient solution system. Isolates of Pythium aphanidermatum , Pythium irregulare , Pythium ultimum , Phytophthora cinnomomi , Phytophthora nicotianae , Rhizoctonia solani , and
Pythium irregulare, Thielaviopsis basicola , and Cylindrocladium scoparium introduced into soil-less potting media or soil. A secondary objective with the heat treatment was to confirm that pathogens could be eliminated in plastic containers without
Primed, germinated, and untreated seeds of three watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] cultivars were planted in March and April of 1990 and 1991 to evaluate damping-off incited by Pythium irregulare and Rhizoctonia solani AG-4. One week after seeding in 1990, plant stand was greater from primed and germinated than untreated Seeds in noninfested soil and greater from primed than germinated or untreated seeds in soil infested with P. irregulare. Neither germinated nor primed seeds improved plant establishment in soil infested with R. solani AG-4. Early plant stand was greater from the April than the March planting in each year. Plant establishment was more consistent from 'Crimson Sweet' than 'Jubilee' or 'Charleston Gray', but cultivar differences in response to P. irregulare or R. Solani AG-4 were not detected. Primed watermelon Seeds may enhance stand establishment in soil infested with P. irregulare when soil temperature at planting is suboptimal to optimal for watermelon seed germination and growth.
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.
Seedlings of Catharanthus roseus (L.) G. Don `Pacifica Red' were transplanted into substrates composed of either 80% sphagnum peat or coir with the remaining volume being perlite, sand, or vermiculite. The six substrates were inoculated with Pythium irregulare Buisman at 0 or 50,000 oospores per 10-cm container. The containers were irrigated daily to maintain moisture levels near container capacity. No visually apparent symptoms of infection or significant differences in shoot and root fresh and dry weights were observed among the uninoculated substrates and the inoculated coir substrates. Inoculated peat substrates had an 80% infection rate and significantly reduced shoot and root fresh and dry weights as compared to uninoculated substrates. Seedlings of C. roseus were transplanted into pasteurized and unpasteurized substrates composed of 80% (v/v) coir or sphagnum peat with the remaining 20% being perlite. Substrates were inoculated with 0, 5000, or 20,000 oospores of P. irregulare per 10-cm container. No visually apparent symptoms of infection or significant differences in shoot and root fresh and dry weights were observed among the uninoculated substrates and the inoculated pasteurized coir. The inoculated pasteurized peat substrate, inoculated unpasteurized peat substrate, and the inoculated unpasteurized coir substrate grown plants had an 88% infection and a significant reduction in the shoot and root fresh and dry weights.
Mandelbaum, 1986 ; Lumsden et al., 1983 ; Zhang et al., 1996 ). Considering that geranium plants are susceptible to root diseases caused by a multitude of pathogens, including numerous Pythium species such as P. splendens ( Griffin, 1972 ), P. ultimum