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Thursday, March 21, 2019


Browse on keywords: disease wheat take-all

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Search results on 03/21/19

1424. Cook, R.J.. 1988. Management of the environment for the control of pathogens.. Phil. Trans. R. Soc. London B 318:171-182.
Pathogens can be controlled by management of the environment of 1) the host plant, to maximize resistance, 2) non-pathogens associated with the pathogen to enhance antagonisms, and 3) the pathogen itself, to limit its activity or longevity directly. Often only the slightest change in the environment will bring about a major change in disease activity, such as drying of the soil. The quality and quantity of non-pathogens are both important, and contribute to more complexity, and usually more biological stability. Fusarium foot rot of wheat first was a serious problem in the low- to intermediate-rainfall areas, particularly with the more progressive farmers. This was traced to the occurrence of severe plant water stress triggered by excessive nitrogen fertilization. By managing plant water potentials, the parasitic activities of Fusarium culmorum are virtually prevented. By leaving standing stubble, the saprophytic activities of this fungus are virtually prevented. Pythium root rot generally requires control only in the intermediate- to high-rainfall areas. The most effective controls are combinations that 1) minimize wheat straw on the surface or in the top 10-15 cm soil, 2) keep the soil surface exposed to drying winds and sun, especially in early growth, and 3) keep soil matric potentials in the top soil drier than -0.4 to -0.5 bar. Straw can be eliminated by burning, burial, or rotation (peas, lentils). Fumigation of the soil, not the straw, is necessary to eliminate the pathogens. Pythium is also limited by early seeding, and is less prevalent in soils without a tillage pan. To maximize take-all antagonism, tillage and delayed seeding can be used. Also the use of ammonium rather than nitrate fertilizer suppresses take-all, and any fertilizer will suppress it on an N-starved soil.

2434. Hanson, J.. 1989. researchers track possible wheat protecting bacteria.. Daily Evergreen, WSU, Pullman, WA; Sept. 8, p.1..
Research by UDSA scientists with a genetically altered bacteria to control take-all in wheat, were able to track the movement of the organism in the soil. An unexpected infection with rhizoctonia occurred and obscured results.

10814. Heim, M., R.J. Cook, and D.J. Kirpes. 1986. Economic benefits and costs of biological control of take-all to the Pacific Northwest wheat industry.. Research Bulletin 0988, Agr. Res. Center, Washington State Univ., Pullman, WA.
Take-all can severely lower wheat yields. One possible control is through the use of antagonistic Pseudomonad bacteria applied to wheat seed. Disease surveys in the region verified increased disease problems with grain intensive rotations and with reduced till or no-till farming. Overall, an estimate 600,000 acres are affected by take-all in the region. Estimates of the cost of a commercial bacterial seed treatment were $14.30/ac applied. Wheat yields were assumed to increase an average of 5-10% from this. At a wheat price of $3.00/bu, a minimum 5 bu/ac increase is needed to break even on the treatment.

10988. Cook, R.J.. 1981. The influence of rotation crops on Take-all decline phenomenon.. Phytopathology 71:189-192.
Five rotation crops (potatoes, oats, alfalfa, beans, grass) were tested for their ability to promote take-all decline in continuous wheat. Take-all from natural inoculum was common on wheat plants in plots previously planted to wheat, grass, or soybeans, but was mild or nonexistent on wheat after oats, potatoes, or alfalfa. When inoculum was introduced, take-all was severe in plots previously planted to potatoes, oats, alfalfa, or beans, whether or not the soil had been fumigated. In contrast, soil in plots previously planted to wheat or the grass mixture had to be fumigated before disease of such severity could develop in response to introduced inoculum. Soils cropped continuously to wheat or wheat in rotation with grass were suppresive to take-all; the other crops resulted in soil becoming highly conducive to take-all.

10998. Reis, E.M., R.J. Cook, and B.L. McNeal. 1982. Effect of mineral nutrition on take-all of wheat.. Phytopathology 72:224-229.
Take-all developed on significantly fewer roots when P.K. and Mg were made available to the wheat roots at twice, compared with one-half, the concentration in normal Hoagland's solution, and resulted in the greatest increase in root growth. Ca and S had no significant effect on disease or root growth. Nitrate N increased the number of roots but did not influence disease. Zn and Cu treatments each resulted in more roots and less take-all. Mn, and possibly Fe, had suppresive effects on take-all. Field tests showed disease reduction with certain of the nutrient treatments.

11085. Cook, R.J. and A.D. Rovira. 1976. The role of bacteria in the biological control of Gaeumannomyces graminis by suppresive soils.. Soil Biol. Biochem. 8:269-273.
The suppresion of take-all by certain soils or following certain soil treatments is considered to be an expression of either specific or general antagonism. Specific antagonism is effective in dilutions as high a 1 in 1000, can be transferred from soil to soil, operates near or on wheat roots, is destroyed by 60 C moist heat, is fostered by wheat monoculture, but may be lost by fallow or rotation with certain crops, especially legume hay or pasture. Strains of Pseudomonas fluorescens may be involved. General antagonism is a soil property which cannot be transferred and is resistant to 80 C heat, to chemical fumigation, but not to autoclaving. Take-all control by organic amendments, minimum tillage, or a soil temperature of 28 C may be expressions of increased general antagonism. In southern Australia, take-all losses can be very heavy. Some general antagonism occurs, but seldom any specific antagonism. Both types occur in dryland wheat areas of the Pacific Northwest, where take-all is virtually non-existent.

11095. Smiley, R.W. and R.J. Cook. 1973. Relationship between take-all of wheat and rhizosphere pH in soils fertilized with ammonium vs. nitrate nitrogen.. Phytopathology 63:882-890.
Take-all of wheat was reduced by ammonium fertilizer supplemented with N-Serve to slow nitrification, but was severe with no added N, or with calcium nitrate at N rates equivalent to that supplied by ammonium. The addition of lime negated the control of ammonium. A good correlation existed between rhizosphere pH and disease severity, but not with bulk soil pH. The rhizosphere pH dropped with ammonium uptake, increased with nitrate uptake, and remained unchanged with no added N. Disease severity was progressively less as rhizosphere pH dropped below 7, and was greatly reduced below 6.6. In a fumigated soil, disease was controlled only when pH was below 5. Reduced disease severity apparently resulted from direct inhibition of the pathogen at pH less than 5 and indirect inhibition (possibly a biocontrol) above 5.

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