Mycorrhizal fungi can increase the quality of a harvest, as the experiments with basil, strawberries, tomatoes and wheat illustrate. They can also increase the ability of crops to compete with weeds and enhance their resistance to diseases by priming plants’ immune systems. They can make crops less susceptible to drought and heat, and more resistant to salinity and heavy metals. They even boost the ability of plants to fight off attacks from insect pests by stimulating the production of defensive chemicals.