A pythium root rot of muskmelon

1968 ◽  
Vol 46 (10) ◽  
pp. 1165-1171 ◽  
Author(s):  
C. D. McKeen ◽  
H. J. Thorpe
Keyword(s):  
Experimental Data ◽  
Root Rot ◽  
Pythium Ultimum ◽  
Wilt Disease ◽  
Field Soil ◽  
Southern Ontario ◽  
Pythium Root Rot ◽  
High Soil ◽  
Infested Field ◽  
Soil Temperatures

Pythium ultimum was readily isolated from the necrotic roots of young and mature muskmelon plants growing in soil in which root rot had been severe. Muskmelons planted in steamed soils inoculated with P. ultimum developed necrotic roots and aboveground symptoms closely similar to those produced in naturally infested field soil. The fungus was considerably more pathogenic at low than at high soil temperatures. All of seven commercial varieties of muskmelon commonly grown in southern Ontario were moderately to highly susceptible to P. ultimum. Experimental data support the conclusion that P. ultimum probably plays an important role in the "sudden wilt" disease of mature muskmelon plants.

scholarly journals White Root Rot of Raspberries

1951 ◽  
Vol 4 (3) ◽  
pp. 211
Author(s):  
GC Wade
Keyword(s):  
Soil Moisture ◽  
Root Rot ◽  
Soil Moisture Content ◽  
Soil Conditions ◽  
Causal Organism ◽  
White Root Rot ◽  
High Soil Moisture ◽  
High Soil ◽  
Soil Temperatures ◽  
Dry Soil

The disease known as white root rot affects raspberries, and to a less extent loganberries, in Victoria. The causal organism is a white, sterile fungus that has not been identified. The disease is favoured by dry soil conditions and high soil temperatures. It spreads externally to the host by means of undifferentiated rhizomorphs; and requires a food base for the establishment of infection. The spread of rhizomorphs through the soil is hindered by high soil moisture content and consequent poor aeration of the soil.

scholarly journals Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives

2006 ◽  
Vol 32 (4) ◽  
pp. 307-321 ◽  
Author(s):  
John Clifford Sutton ◽  
Coralie Rachelle Sopher ◽  
Tony Nathaniel Owen-Going ◽  
Weizhong Liu ◽  
Bernard Grodzinski ◽  
...  
Keyword(s):  
Nutrient Solution ◽  
Root Rot ◽  
Root Zone ◽  
Pythium Ultimum ◽  
Stress Factors ◽  
Pythium Root Rot ◽  
Whole Plant ◽  
Phenolic Substances ◽  
Hydroponic Systems ◽  
The Impact

The etiology and epidemiology of Pythium root rot in hydroponically-grown crops are reviewed with emphasis on knowledge and concepts considered important for managing the disease in commercial greenhouses. Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems around the world including cucumber, tomato, sweet pepper, spinach, lettuce, nasturtium, arugula, rose, and chrysanthemum. Principal causal agents include Pythium aphanidermatum, Pythium dissotocum, members of Pythium group F, and Pythium ultimum var. ultimum. Perspectives are given of sources of initial inoculum of Pythium spp. in hydroponic systems, of infection and colonization of roots by the pathogens, symptom development and inoculum production in host roots, and inoculum dispersal in nutrient solutions. Recent findings that a specific elicitor produced by P. aphanidermatum may trigger necrosis (browning) of the roots and the transition from biotrophic to necrotrophic infection are considered. Effects on root rot epidemics of host factors (disease susceptibility, phenological growth stage, root exudates and phenolic substances), the root environment (rooting media, concentrations of dissolved oxygen and phenolic substances in the nutrient solution, microbial communities and temperature) and human interferences (cropping practices and control measures) are reviewed. Recent findings on predisposition of roots to Pythium attack by environmental stress factors are highlighted. The commonly minor impact on epidemics of measures to disinfest nutrient solution as it recirculates outside the crop is contrasted with the impact of treatments that suppress Pythium in the roots and root zone of the crop. New discoveries that infection of roots by P. aphanidermatum markedly slows the increase in leaf area and whole-plant carbon gain without significant effect on the efficiency of photosynthesis per unit area of leaf are noted. The platform of knowledge and understanding of the etiology and epidemiology of root rot, and its effects on the physiology of the whole plant, are discussed in relation to new research directions and development of better practices to manage the disease in hydroponic crops. Focus is on methods and technologies for tracking Pythium and root rot, and on developing, integrating, and optimizing treatments to suppress the pathogen in the root zone and progress of root rot.

scholarly journals First Report of Pythium Root Rot on Grain Sorghum in Mississippi

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 922-922 ◽  
Author(s):  
K. S. McLean ◽  
G. W. Lawrence
Keyword(s):  
Root Rot ◽  
Pathogenic Fungus ◽  
Pythium Ultimum ◽  
Grain Sorghum ◽  
Growth Chamber ◽  
Thick Wall ◽  
Field Soil ◽  
Tissue Sections ◽  
Millet Seed ◽  
Collar And Root Rot

In May 2000, seedling death in grain sorghum (Sorghum bicolor L.) was reported in fields located in the delta region of Mississippi, following a wet planting season when precipitation and relative humidity were 50 and 10.5% greater, respectively, than the 5-year average. Seedlings exhibited various symptoms, including necrosis of the leaf tip and blade, collar rot, root rot, and streaking of the vascular system at the soil line that resulted in plant death. Tissue sections from plants with collar and root rot were plated aseptically on potato dextrose, V8, and cornmeal agars. Pythium ultimum was the only pathogenic fungus isolated and appeared on 63% of tissue sections. Recovered isolates exhibited similar growth and morphology in vitro and were stimulated to produce fruiting structures by the grass leaf-baiting method. Isolates produced primary terminal globose oogonia, 19 μm in diameter. Oospores were aplerotic and approximately 16.4 µm in diameter, with a 2.1-μm-thick wall. Antheridia were monoclinous or diclinous and short-stalked, with 1 to 2 antheridia per oogonium. Zoospores were produced only in sterile water grass blade cultures and were reniform and biciliate, erupting from spherical vesicles in groups of 15 to 30. Pathogenicity tests were conducted in a controlled growth chamber. P. ultimum was increased on sterile common millet seed and incorporated into sterile field soil at an 0.5% (vol/vol) ratio. Noninfested millet seed was incorporated into field soil as a control. Soil was placed in pots, planted with five-grain sorghum seed, and placed in a growth chamber at 5°C, with a 12-h photoperiod. Treatments were replicated five times, and the experiment conducted twice. At 21 days after planting, the inoculated grain sorghum plants developed collar and root rot, with some leaf necrosis, similar to symptoms observed in the field. Symptoms did not develop on the control plants. Reisolations of P. ultimum on corn meal agar and by the grass-baiting method were successful. P. ultimum commonly is in Mississippi soils and is pathogenic to a number of agronomic crops, although it has not been reported previously as a pathogen on grain sorghum in Mississippi.

scholarly journals Efficacy of Various Biological Control Agents and Biorationals against Pythium Root Rot in Poinsettia

2003 ◽  
Vol 13 (1) ◽  
pp. 149-153 ◽  
Author(s):  
M. Little ◽  
W. Brown ◽  
T.J. Blom ◽  
J.A. Gracia-Garza ◽  
K. Schneider ◽  
...  
Keyword(s):  
Root Rot ◽  
Pythium Ultimum ◽  
Common Disease ◽  
Root Weight ◽  
Environmental Implications ◽  
Biological Origin ◽  
Development Of Resistance ◽  
Pythium Root Rot ◽  
Significant Difference ◽  
Legitimate Concern

Pythium root rot (Pythium spp.) is a common disease of greenhouse-grown poinsettias (Euphorbia pulcherrima) that can cause serious plant loss or reduction in plant quality. Application of effective chemical fungicides to poinsettia plants has reduced losses due to Pythium; however, development of resistance to these fungicides is a legitimate concern, as well as the environmental implications of using chemical pesticides. In this study, a group of products of biological origin and known biocontrol agents were evaluated for their efficacy to control pythium root rot of poinsettia. These products and organisms were compared to metalaxyl (Ridomil), a fungicide commonly used to reduce losses to Pythium. The results showed that two products based on two different species of Streptomyces, Mycostop and Actino-Iron, were as effective as metalaxyl at reducing the symptoms associated with pythium root rot when artificially inoculated with Pythium ultimum var. ultimum compared to the control plants. Many roots remained functional throughout the duration of the experiments and the overall appearance and number of bracts of commercial quality of the plants were similar for the three treatments mentioned above. In an additional experiment, Mycostop was tested in combination with a single application of metalaxyl either at 3, 7, or 11 weeks after transplanting. Plants inoculated with P. ultimum var. ultimum and treated with metalaxyl either on week 3 or 7 after transplanting in combination with two applications of Mycostop, had greater fresh root weight than those only treated with metalaxyl at week 11 or the chemical control (three applications of metalaxyl). However, there was no significant difference in the number of bracts or the bract diameter between plants treated with metalaxyl at weeks 3 or 7 followed by Mycostop and those plants treated with the fungicide alone. A reduction in the amount of fungicide used to control pythium root rot can be achieved when used in combination with a biocontrol agent without compromising the health of poinsettias.

scholarly journals Pythium Root Rot and Growth Responses of Organically Grown Geranium Plants to Beneficial Microorganisms

HortScience ◽  
2009 ◽  
Vol 44 (6) ◽  
pp. 1622-1627 ◽  
Author(s):  
Valérie Gravel ◽  
Claudine Ménard ◽  
Martine Dorais
Keyword(s):  
Pseudomonas Putida ◽  
Root Rot ◽  
Dry Weight ◽  
Pythium Ultimum ◽  
Organic Production ◽  
Plant Production ◽  
Trichoderma Atroviride ◽  
Growth Responses ◽  
Pythium Root Rot ◽  
Organically Grown

Pythium root rot, caused by Pythium ultimum, is responsible for important losses in geranium plant production, mainly as a result of the decrease in the plant overall quality. An organic production system for geranium plants based on fertilization using a filtered suspension of dehydrated hen manure was compared with a conventional fertilization system to evaluate their tolerance to root disease. Under typical greenhouse conditions, geranium plants were inoculated with a suspension of Pseudomonas putida, Trichoderma atroviride, a mixture of both or with Trichoderma harzianum, and a commercially available product, Rootshield®, 1 and 4 weeks after planting. Four weeks after the first inoculation, Pseudomonas putida and Trichoderma atroviride stimulated plant growth (shoot and root dry weight) compared with the control regardless of the fertilization. The results also showed that the colonization of geranium roots by Pythium spp. was significantly lower for organically grown plants for all treatments compared with the inoculated control under conventional fertilization. Inoculation with T. atroviride under conventional fertilization was the only treatment that did not significantly reduce root colonization by Pythium spp. compared with the conventional control. For both organically and conventionally grown plants, the coinoculation with both P. putida and T. atroviride resulted in the weakest colonization of roots by the pathogen. The inoculation of P. putida, T. atroviride, and the mixture of the bacterium and the fungus also significantly increased the fresh and dry weight of roots regardless of the fertilization used. All microorganism treatments in conventionally grown plants significantly increased the fresh and dry weight of the shoot compared with the control.

scholarly journals Weed Hosts of the Sugarcane Root Rot Pathogen, Pythium arrhenomanes

Plant Disease ◽  
1997 ◽  
Vol 81 (6) ◽  
pp. 587-591 ◽  
Author(s):  
N. Dissanayake ◽  
J. W. Hoy ◽  
J. L. Griffin
Keyword(s):  
Symptom Severity ◽  
Root Rot ◽  
Root Colonization ◽  
Italian Ryegrass ◽  
Field Soil ◽  
Purple Nutsedge ◽  
Treated Soil ◽  
Pythium Arrhenomanes ◽  
Pythium Root Rot ◽  
Weed Hosts

Weeds in the Poaceae and Cyperaceae families prevalent in sugarcane fields were evaluated as potential hosts for the root rot pathogen, Pythium arrhenomanes. In greenhouse studies, bermudagrass, broadleaf signalgrass, browntop panicum, barnyardgrass, large crabgrass, goosegrass, itchgrass, johnsongrass, Italian ryegrass, and purple nutsedge became infected when grown in steam-treated soil infested with P. arrhenomanes. However, the extent of root colonization, symptom severity, and growth reductions varied among species. Symptom severity and root colonization by P. arrhenomanes were less when weeds were grown in sugarcane field soil in the greenhouse than when weeds were grown in Pythium-infested, steam-treated field soil. Levels of root colonization by P. arrhenomanes in both experiments were greatest for johnsongrass and itchgrass and lowest for browntop panicum, goosegrass, and Italian ryegrass. For weeds collected from sugarcane fields, frequencies for colonized plants were moderate to high, but the extent of root colonization by P. arrhenomanes was low for all except johnsongrass. The results indicate that weeds can serve as hosts for P. arrhenomanes and may play roles in the epidemiology of Pythium root rot on sugarcane.

scholarly journals Using Commercial Compost as Control Measures against Cucumber Root-Rot Disease

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Kamel Kamal Sabet ◽  
Magdy Mohamed Saber ◽  
Mohamed Adel-Aziz El-Naggar ◽  
Nehal Samy El-Mougy ◽  
Hatem Mohamed El-Deeb ◽  
...  
Keyword(s):  
Root Rot ◽  
Control Measure ◽  
Disease Incidence ◽  
Pathogenic Fungi ◽  
Pythium Ultimum ◽  
Control Measures ◽  
Infested Soil ◽  
Fungal Isolates ◽  
Cucumber Root

Five commercial composts were evaluated to suppress the root-rot pathogens (Fusarium solani (Mart.) App. and Wr, Pythium ultimum Trow, Rhizoctonia solani Kuhn, and Sclerotium rolfsii Sacc.) of cucumber plants under in vitro and greenhouse conditions. In vitro tests showed that all tested unautoclaved and unfiltrated composts water extracts (CWEs) had inhibitor effect against pathogenic fungi, compared to autoclaved and filtrated ones. Also, the inhibitor effects of 40 bacteria and 15 fungi isolated from composts were tested against the mycelial growth of cucumber root-rot pathogens. Twenty two bacteria and twelve fungal isolates had antagonistic effect against root-rot pathogens. The antagonistic fungal isolates were identified as 6 isolates belong to the genus Aspergillus spp., 5 isolates belong to the genus Penicillium spp. and one isolate belong to the genus Chaetomium spp. Under greenhouse conditions, the obtained results in pot experiment using artificial infested soil with cucumber root-rot pathogens showed that the compost amended soil reduced the percentage of disease incidence, pathogenic fungi population, and improved the cucumber vegetative parameters as shoot length, root length, fresh weight, and dry weight. These results suggested that composts are consequently considered as control measure against cucumber root-rot pathogens.

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