ABSTRACT

Several terms such as distribution, dissemination, dispersal, spread, and transmission have been used invariably and rather loosely. Since most of the cultivated crops are raised from seed the transmission of diseases and transport of pathogens by seeds has much importance for plant pathologists and fanners. Pathogens perpetuating in soil either saprophytically on plant debris or in dormant stage are transported from one place to another within a plot or from one plot to another or even from one area to another area. Spores that are extruded in gelatinous tendrils that may harden when dry can be separated from each other and washed down trees and other kinds of plants during rain or heavy dews. Spread of fungal pathogens by insects, although accidental, is fairly widespread especially for those diseases in which pathogens produce sugary and sticky substances. Surface water resulting from rains or irrigation is known to disseminate the inoculum of several pathogens.