Download or read book Investigations on Footrot of Winter Wheat Caused by Cercosporella Herpotrichoides Fron written by Lester Emert Dickens and published by . This book was released on 1957 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Initiation and Spread of Footrot of Wheat Caused by Cercosporella Herpotrichoides written by Randall Charles Rowe and published by . This book was released on 1972 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Footrot of wheat (Cercosporella herpotrichoides Fron) is a major disease of winter wheat in certain areas of the world having a cool, damp winter and early spring climate. In Oregon, it is an economic problem in the higher rainfall wheat-growing areas in the eastern portion of the state. This study was undertaken to obtain basic information concerning inoculum production, initiation of infection and epidemic development of this disease. The activity of the fungus is strongly controlled by its microclimate, requiring cool, damp conditions for optimal activity. Temperature is the primary factor regulating inoculum production, as abundant moisture is not usually a limiting factor under field conditions from late fall through early spring. Maximum sporulation occurred at 10 C, decreased to insignificant amounts above 20 C and ceased below 0 C and above 30 C. Under fluctuating temperatures, abundant sporulation continued when day temperatures were in the optimal range (8-12 C), as long as the duration of sub-0 C night temperatures ( -5 C) did not exceed 14 hrs. A method of evaluating fluctuating temperature regimes was developed by calculating Daily Thermal Sporulation Coefficients (DTSC). The amount of sporulation is a function of the total hours of favorable and unfavorable temperatures that occur daily as reflected by DTSC values. Active sporulation periods are defined as periods of at least 2-3 weeks duration in which the humidity near the soil remains near saturation, the air temperature is above freezing for more than 8 hrs /day, and the average DTSC is above 50. Maximum sporulation levels can be maintained continuously up to 50 days under these conditions. Sporulation periods were identified from field temperature data and used to assess seasonal epidemic potential. The temperature range over which infection can occur is identical to that for sporulation. Infection requires free moisture and is stimulated by the presence of exogenous nutrients, while continued high humidity favors lesion development. All aerial plant tissues, including leaf blades, are susceptible to infection if these requirements are met; susceptibility increasing with tissue age. Infection occurs naturally at the base of the plant by colonization of senescent leaf sheaths, enabling the fungus to establish a food base and increase its infection potential. Rapid colonization of these tissues also provides a protected infection court free from moisture stress, enabling the fungus to overcome the resistance of underlying green tissues. Movement of infection from point sources of inoculum was evaluated in the field. Slopes of disease gradients calculated by plotting the log percent infection against the log distance from the inoculum source were less than slopes calculated from a rain splash model system and decreased throughout the growing season. The effective dispersal range of the fungus was only 3-4 feet. Plants located 3 feet from the inoculum source showed 50% infection 88 days later than those located 1 foot away. Apparent infection rates (r) were low (.005-.011) as compared with cereal rusts (. 100 -. 500). An increase in r was noted in mid-spring in plots with inoculum but not in plots where the inoculum was removed. This indicates that early spring as well as late fall is an important infection period. Analysis of the data fits Van der Plank's "simple interest" model which suggests no role for secondary inoculum in the disease cycle. This is supported by field observations showing abundant sporulation on stubble and negligible amounts on new lesions.

Download or read book Eyespot Footrot of Winter Wheat Caused by Cercosporella Herpotrichoides written by Lester E. Dickens and published by . This book was released on 1964 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Initiation and Spread of Footrot of Wheat Caused by Cercosporella Herpotrichoides Fron written by Randall Charles Rowe and published by . This book was released on 1973 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Etiological Studies on Foot Rot of Wheat Caused by Cercosporella Herpotrichoides Fron written by Ralph S. Byther and published by . This book was released on 1968 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abundant conidial production occurs from colonized straws and plants infected with Cercosporella herpotrichoides Fron during the cool moist months of the growing season. Experiments were designed to study the survival, inoculum potential and competitive saprophytic ability of conidia in soil. Laboratory results indicated that cool moist soil favors the saprophytic survival of the fungus in soil. Viable hyphae were observed 16 months after conidia were buried in soil held at 5° and 10° C. Ammonium nitrate inhibited germination and survival of conidia in soil. It also inhibited germination on glass slides not in contact with soil. Ammonium ions were more inhibitory than nitrate ions. Glucose did not influence germination but stimulated saprophytic development and survival of the pathogen in soil. A marked reduction in survival of C. herpotrichoides after one year occurred in naturally and artificially colonized straws buried in the soil. Survival was favored in straws placed at the soil surface. Straws buried in conidial infested soil and incubated in the laboratory or the field were colonized by the pathogen. Colonization was directly related to the inoculum density of the soil and inversely related to time. Foot rot lesions developed below the soil surface on plants grown in conidial infested soil. Lesion incidence was directly related to the inoculum density of the soil. Based on mathematical models it was concluded that conidia were influenced by host exudates only at the host surface and a rhizosphere was not operative. The fungus was able to grow up to 10 mm from a food base in the soil and cause below ground lesions. Lesions below the soil surface were observed on plants growing under natural field conditions. It is suggested these below ground infections play an important part in maintaining inoculum levels in fields during years not favorable for foot rot development. In growth chamber studies, plants developed lesions from single conidium inoculations. Disease development on plants in the growth chamber was influenced by the general susceptibility of the inoculated tissue, the stage of growth when inoculated, the rate of plant growth and the openness of the crown. Green tissues were more resistant to infection than senescent tissues. Infection occurring before the onset of tillering can result in lesion development on each new tiller produced. Plants growing rapidly in a high nitrogen media were able to slough off infections and escape the disease. Tight crowned plants tended to have a majority of their tillers infected while healthy culms were associated with diseased ones in plants having wide spreading crowns. Successful penetration and infection of a coleoptile or leaf sheath did not insure disease development. The infected tissues may become separated from the main stem before the fungus has penetrated into adjacent leaf sheaths, thus isolating the pathogen, so that.the majority of the plant tissue escapes infection. The infection process failed at one of three stages on green "resistant" tissues of coleoptiles and leaf sheaths: (1) germination failed to occur, (2) germination occurred but the pathogen failed to attempt penetration, and (3) penetration was attempted but failed. Thickening of host cell walls was associated with the failure of attempted penetrations. Thickened host walls were also associated with containment of the pathogen at the perifery of lesions. These thickened cell walls usually stained heavily with cotton blue and were never associated with senescent tissue. Results indicate that stubble mulching and deep seeding would favor foot rot development. Chemicals or varieties delaying senescence of leaf sheaths would be expected to reduce foot rot injury.

Download or read book Cercosporella Foot Rot of Winter Cereals written by Roderick Sprague and published by . This book was released on 1934 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Technical Bulletin written by and published by . This book was released on 1935 with total page 1022 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Journal of Agricultural Research written by and published by . This book was released on 1937 with total page 1026 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sporulation by Cercosporella Herpotrichoides Fron on Wheat Stems Exposed in Soil Seeded with Fungi Isolated from Wheat Rhizosphere written by Charles Marion Howard and published by . This book was released on 1969 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Relation of Fertilizers to the Control of Cotton Root Rot in Texas written by Howard Vernon Jordan and published by . This book was released on 1934 with total page 1022 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Plant Disease Reporter written by and published by . This book was released on 1977 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spore Production of Cercosporella Herpotrichoides Fron written by Flora E-Wa Pang and published by . This book was released on 1961 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Plant Disease Bulletin written by and published by . This book was released on 1972 with total page 1208 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Plant Disease Reporter written by and published by . This book was released on 1930 with total page 1008 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Annual Report of the New York State College of Agriculture and Life Sciences at Cornell University the Cornell University Agricultural Experiment Station written by New York State College of Agriculture and published by . This book was released on 1956 with total page 1624 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Legislative Document written by New York (State). Legislature and published by . This book was released on 1959 with total page 1506 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Annual Report of the New York State College of Agriculture at Cornell University and the Agricultural Experiment Station written by New York State College of Agriculture and published by . This book was released on 1955 with total page 1108 pages. Available in PDF, EPUB and Kindle. Book excerpt: