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 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.

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.

Management of Pythium myriotylum in Tobacco Transplant Production Greenhouses

2021 ◽  
Author(s):  
Xuemei Zhang ◽  
Chuck Johnson ◽  
David T Reed
Keyword(s):  
Root Length ◽  
Root Rot ◽  
Untreated Control ◽  
Copper Ion ◽  
Positive Control ◽  
Common Disease ◽  
Management Tools ◽  
Pythium Root Rot ◽  
Tobacco Seedlings ◽  
Root Tissues

Pythium root rot is a common disease that can threaten tobacco seedling production in greenhouses. However, management tools are limited in tobacco transplant production greenhouses. To identify additional Pythium control options, oomyceticide treatments (ethaboxam, mefenoxam, and copper ethanolamine complex) and non-oomyceticide (ultraviolet light and copper ion) water treatments were compared with etridiazole and an untreated control on TN 90LC tobacco seedlings inoculated with P. myriotylum in greenhouses. All the treatments in oomyceticide trials were applied to the bay water once before inoculation, when seedling roots had extended into the water. The inoculum was applied immediately before seeding in non-oomyceticide trials, where etridiazole was applied to bay water once, two weeks after seeding, as a positive control. Non-oomyceticide treatments were applied three times: 24 hours before, two weeks after, and four weeks after seeding. At the end of the tobacco transplant production season, ethaboxam and mefenoxam significantly (P<0.05) reduced root rot incidence and severity by as high as 100%, compared with the untreated control. Ethaboxam and mefenoxam also significantly (P<0.05) reduced oospores produced in infected root tissues, while significantly (P<0.05) increasing root length and weight. Ultraviolet radiation and copper ion treatments had no significant effects on tobacco seedling root length or weight compared with the untreated control, although the copper ion treatments significantly (P<0.05) reduced root rot severity and oospores produced in root tissues. Similar to etridiazole, ethaboxam and mefenoxam consistently reduced the AUDPC of Pythium root rot, but copper ion treatments only reduced AUDPC significantly (P<0.05) in one trial.

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 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.

scholarly journals Temperature, Moisture, and Seed Treatment Effects on Rhizoctonia solani Root Rot of Soybean

Plant Disease ◽  
2003 ◽  
Vol 87 (5) ◽  
pp. 533-538 ◽  
Author(s):  
A. E. Dorrance ◽  
M. D. Kleinhenz ◽  
S. A. McClure ◽  
N. T. Tuttle
Keyword(s):  
Soil Moisture ◽  
Rhizoctonia Solani ◽  
Root Rot ◽  
Seed Treatment ◽  
Anastomosis Group ◽  
Control Measures ◽  
Root Weight ◽  
Wide Range ◽  
Plant Stand ◽  
Growth Chamber Studies

The effects of temperature and soil moisture on infection and disease development by Rhizoctonia solani on soybean were studied individually. In addition, the anastomosis group of R. solani isolates recovered from soybean from 35 fields in 15 counties was determined. All of the 44 isolates recovered in this study were AG-2-2 IIIB. Five isolates of R. solani were able to infect and colonize soybean roots and hypocotyls at 20, 24, 28, and 32°C in growth chamber studies. The temperatures evaluated in this study were not limiting to the isolates tested. In greenhouse studies, nine R. solani isolates and a noninoculated control were evaluated at 25, 50, 75, and 100% soil moisture holding capacity (MHC). Root weights were greater and percent stand averages higher at 50 and 75% than at 25 or 100% MHC; however, as percentage of control, the main effect on percent moisture for percent stand, plant height, or root weight was not significant. There were significant differences among the isolates for the percent stand, root rot rating, and root fresh weight of soybean in each study. In both temperature and moisture studies, the R. solani isolates could be separated as predominantly causing (i) seed rot, as detected by greatly reduced plant stand; (ii) root rot generally having no effect on plant stand but a high root rot rating and low root weight; or (iii) hypocotyl lesions, having no effect on plant stand, a low root rot score, and a high number of red lesions on the hypocotyl. In the greenhouse seed treatment evaluations of five fungicides, there was no fungicide by isolate interaction using these pathogenic types of R. solani. None of the seed treatments evaluated in this study provided 100% control of the four isolates tested. Due to the wide range of environmental factors that permit R. solani infection and disease on soybeans, other control measures that last all season, such as host resistance, should be emphasized.

scholarly journals The Root Rot-Fusarium Wilt Complex of Peas

1963 ◽  
Vol 16 (1) ◽  
pp. 55 ◽  
Author(s):  
A Kerr
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Root Rot ◽  
Fungal Pathogens ◽  
South Australia ◽  
Pythium Ultimum ◽  
Wilt Symptom ◽  
Intensive Cropping ◽  
Race 2

At least four fungal pathogens are involved in the root rot-Fusarium wilt complex of peas which is a serious problem following intensive cropping of peas in South Australia. The pathogens are Fusarium oxysporum f. pisi race 2 Snyder & Hansen, F. solani f. pisi Snyder & Hansen, Pythium ultimum Trow, and Ascochyta pinodella L. K. Jones. In susceptible pea cultivars there is a marked interaction between F. oxysporum and P. ultimum. P. ultimum alone causes initial stunting from which plants gradually recover; F. OX1Jsporum alone probably CRuses little damage; both fungi together CRuse initial stunting followed by severe wilt symptom about 6 weeks after sowing and death 2 weeks later. The importance ofF. solani and A. pinodella has not been fully determined, but they probably cause only minor damage.

Identification of metalaxyl and ethaboxam insensitive Pythium sylvaticum pathogenic to pulse crops in Montana, USA.

2021 ◽  
Author(s):  
Lipi Parikh ◽  
Swarnalatha Moparthi ◽  
Frankie Crutcher ◽  
Mary Burrows
Keyword(s):  
Root Rot ◽  
Damping Off ◽  
Management Options ◽  
Fungicide Sensitivity ◽  
Root Rots ◽  
Pulse Crops ◽  
Pythium Root Rot ◽  
Pythium Sylvaticum ◽  
Potential Pathogenicity

Pythium root rot and damping-off caused by Pythium spp. are important diseases of pulse crops. In a 2016 pathogen survey from dry pea growing fields in Montana, along with commonly known causal agents P. ultimum and P. irregulare, an isolate identified as P. sylvaticum (LPPY17) was isolated from the rhizosphere of a diseased pea plant collected from Valley County, MT. Root rots and damping-off caused by P. sylvaticum have not previously been reported for chickpea, pea, and lentil crops. The isolate LPPY17 was tested for fungicide resistance in vitro, and results indicated a reduced sensitivity to metalaxyl and ethaboxam containing fungicides. LPPY17 was also tested for pathogenicity on chickpea, pea, and lentil seedlings in the greenhouse, and the results from the study revealed LPPY17 is capable of causing both root rots and damping off. Due to the potential pathogenicity and reduced fungicide sensitivity of this species, in the future it will be important to monitor for P. sylvaticum in pulse root rot surveys and diagnostics, as management options may be different from other common Pythium spp.

STUDIES ON BROWNING ROOT ROT OF CEREALS: VI. FURTHER CONTRIBUTIONS ON THE EFFECTS OF VARIOUS SOIL AMENDMENTS ON THE INCIDENCE OF THE DISEASE IN WHEAT

1940 ◽  
Vol 18c (6) ◽  
pp. 240-257 ◽  
Author(s):  
T. C. Vanterpool
Keyword(s):  
Root Rot ◽  
Nutrient Deficiencies ◽  
Sweet Clover ◽  
Poor Growth ◽  
Prairie Soils ◽  
Pythium Root Rot ◽  
The Poor ◽  
Copper Manganese ◽  
Supplemental Nutrients ◽  
Severe Leaf

Further work has substantiated earlier findings that phosphatic fertilizers and farm manure will give adequate control of Pythium root rot of wheat in infested prairie soils. The improvement in growth resulting from these amendments is considered to be due to the production of a larger number of quicker growing roots which lessens the chances for infection and leaves more roots healthy, though the same percentage may be affected as in diseased plants showing severe leaf discolorations. Experiments have failed to indicate that the phosphatic materials increase resistance appreciably. Nitrogenous materials when applied singly had virtually no effect on growth, but once ample phosphorus was added, further nitrogen applications gave substantially greater increases than phosphate alone. Phosphorus is apparently the chief limiting element. No difference was found in preliminary tests in the phosphate-fixing power of browning and normal soils. Typical browning soils responded irregularly to small applications of boron, copper, manganese, or zinc, but were not found to be seriously lacking in these elements. Moderate benefits resulted from heavy applications of gypsum and of sulphur. Browning soil was found also to be deficient in phosphate for non-cereals such as alfalfa, buckwheat, carrots, flax, lettuce, and sweet clover. These crops were not attacked by the Pythium spp. pathogenic to cereals. Consequently the poor growth of the non-cereals in browning soil appears to be due to nutrient deficiencies, while the poor growth of cereals is due to both root-destroying fungi and nutrient deficiencies. In both instances phosphorus is probably the chief limiting element. Ground cereal straw, sweet clover hay, and weed hay amendments gave moderate increases m the growth of wheat. No consistent differences were found in the carbon-nitrogen ratios of browning and normal soils. The results as a whole suggest that two of the most practicable means of meeting the browning root-rot situation are, firstly, to supply supplemental nutrients in the form of artificial fertilizers, and secondly, to add organic residues or farm manure regularly to fields subject to the disease.

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