Some nasty microbes kill or damage plants. In fact, of all the crop destruction by insects, drought and microbes, microbes are responsible for most problems. Microbes cause plants to rot, wilt, spot, lose leaves, pale in color, become stunted, grow tumors, overgrow and die. Microbes causing plant disease include fungi, viruses, and bacteria.
Most plant diseases are caused by pathogenic fungi.
This fungus causes root rot of various plants. Rhizoctonia solani causes root rot in tomatoes.
Some plant diseases, like animal diseases, are caused by viruses.
Many bacteria cause plant diseases.
This bacterium rots onion roots.
Some microbes add nutrients to the soil. Some add nitrogen by fixing it from the atmosphere. These include Rhizobium and Azotobacter which are discussed in the root cellar. Other microbes, such as Mycorrhizal fungi, help supply plants with phosphorus. Please visit the Root Cellar to find out more about microbes that help fertilize the soil.
Wouldn't it be great if farmers didn't have to spray crops with chemicals (pesticides) to kill unwanted destructive insects? Well, thanks to microbes, farmers don't need to use as many chemicals. Farmers are now using microbes to kill unwanted insects. Using organisms such as microbes to kill unwanted pests is called "Biocontrol." Several different microbes are used to kill insects. These microbes can be either viruses, bacteria, fungi or protists.
This virus is widely used to combat many caterpillars, moths, and flies. Although there are over 450 viruses found to kill insects, the most widely studied viruses are the Baculoviruses.
Soil is not just the stuff that gets your hands dirty when you play on the ground. Soil is a complex, living environment necessary for the growth of plants. But how is soil formed? By an interaction of five factors including the action of microbes and other life.
The other factors forming soil are weather, topography, parent material, and time.
When soil is first made, for example after a volcano, some nutrients are missing, including nitrogen and carbon. Therefore, the first organisms to colonize the soil are generally nitrogen fixers and photosynthesizers that fix carbon.