It also destroys volunteer plants that serve as a reservoir of pathogens, such as viruses or rusts, that require a living host. Another way that tillage can affect diseases is through changes in the microenvironment. Reduced tillage, for example, tends to increase soil moisture and decrease soil temperature. These changes suppress some diseases such as dryland foot rot or common root rot. There are numerous other changes in the soil bulk density, porosity, and microbial community that may affect diseases.
Tillage can also affect the behavior of vectors that carry diseases.
For instance, aphids that carry barley yellow dwarf virus are less likely to land in fields with abundant crop residue on the soil surface. The effect of tillage on subsequent disease severity depends heavily on the previous crop. For example, crop debris from wheat contains numerous pathogens which can harm a subsequent wheat crop. Therefore, no-tilling wheat into wheat stubble often results in high disease severity. On the other hand, crop debris from legumes contains very few pathogens that can harm wheat.