Hi Maflobio,

Thank you for sharing your research findings!  I enjoyed reading them.

You are right that there are many microbes can cause disease--some affect humans or other animals, and some can affect plants.  There are many microbes that can be helpful as well.  For example, there are some bacteria that live on or in the plant roots and they can help the plant get nutrients that it needs. 

You have asked a great question about how farmers can deal with plant diseases.  Even on a small scale, I see this issue with my own garden.  Certain types of diseases caused by bacteria or fungi can affect the leaves, roots or fruits of my plants.  There are a variety of options for a farmer:

(1).  They can select plants that are more resistant to disease.  These plants have genetic changes that make them less likely to be affected by the bacteria or fungi.

(2).  They can use chemicals, such as fungicides, that are applied to the crop to prevent the microbes from taking over.

(3).  They can change certain things about the way the crops are grown.  Sometimes farmers will grow plants in a greenhouse, even later in the growing season--this can prevent fungal spores, for example, from blowing in the air and onto the plants.  Personally, I like to add mulch to the ground--this prevents fungi from splashing from the ground to the plants.

(4).  There are some insects that can spread disease--just like a mosquito in some areas of the globe can spread malaria between people, as insects move from plant to plant, they can sometimes spread the disease between the plants.  Some farmers use "beneficial insects:--these insects like to eat the insects that are harmful to the crop.

I hope this helps give you some ideas!  You are exactly right that sometimes, it is not enough--it is possible that a whole crop could be lost.  Farming is a challenging profession that requires a large amount of technical and practical expertise!  By applying some of the solutions above (which ones will depend on farmer's preferences, the buyers' preferences, the type of crop, the cost, etc.), farmers can work against the harmful diseases to their plants.

Sincerely,

Cathy