DISPERSAL OF SPORES AND POLLEN FROM CROPS

Fungal spores and pollens can be dispersed in a number of ways: by ani mals and insects; by water; by wind or by rain. This paper concentrate s on the effects of wind on the dispersal of spores and pollen grains and the effects of rain on spore dispersal. For dispersal to be succes sful particles must complete three phases: removal, dispersal through the air and deposition. The biology of the organism and its environmen t can affect all three phases, however, once released the fate of all airborne particles largely depends on the laws of physics which govern the motion of the air. Many types of spore are actively ejected into the air while others are simply blown from the host surface. Particle size and shape affects dispersal and deposition phases. Local environm ental factors such as temperature, humidity and light, as well as wind or rain, can play a key role in the removal of spores. Wind speed and turbulence or rainfall, largely determine spore dispersal, but, the s ize and shape of the particle, the nature of the plant canopy and the way the particles are released into the air may also be important. Par ticle deposition depends on both environmental and biological factors. This paper briefly considers these processes using examples and how t hey can be modelled.