Use of a specific nematicide on the other hand, will kill nematodes but not the mycorrhizal fungi. Non-target effects on fungi in the soil are now being identified for herbicides used to kill weeds in conservation tillage practices. Crop rotation can also influence the distribution of fungi in soil because of the known host specificity of certain species of fungi. This technique fails, however, for the control of fungi that produce sclerotial structures or spores that survive for long periods in the soil as portentially infective propagules. Moisture manipulation through irrigation and drainage, or compaction of the soil can affect the activity of fungi.
Poor drainage can encourage the growth of soil-borne water molds that cause root rot of some crops.
Similarly, dense plantings create humid environments that encourage the growth of foliar fungi that cause leaf disease and mildews. Return to Top of Document 4. Mycorrhizae are mutualistc associations between plant roots and fungi. These beneficial symbioses are ubiquitous in nature and almost all plant species have some form of mycorrhizal association with fungi. Herbaceous and tree species, both deciduous and coniferous, are receptive to infection by mycorrhizal fungi.