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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.