AIRBORNE BIOLOGICAL MATERIALS 



Aerobiology of Plant and 

 Animal Diseases 



Figure X-7 — COMPONENTS OF A MODEL FOR POLLEN AEROBIOLOGY 



Geographic Plant 

 Distribution 



Antecedent Sun 

 and Rainfall 



"^ 



Catastrophic 

 Events 



PRODUCTION 



Pollen 

 Maturation 



EMISSION 



Day 

 Length 



REFLOTATION 



DISPERSAL 



Settling 

 Rates 



Wind Structure 



DEPOSITION 



Temperature 

 Structure 



Retention by 

 Substrate 



Age Distribution 

 in Stand 



Genetic Pollen Production 

 Potential 



Morphology of Flower 

 for Emission 



Rainfall 



Sunshine 



Relative Humidity 



Atmospheric Turbulence 



Pollen Morphology, 

 "Flight Characteristics" 



Shapes of Plants 

 Vertical and Horizontal 

 Patterns 



Physiography 



h 



Microclimate, Wind Speed 



Temperature, Structure, 



Turbulence 



Rainout 



Atmospheric Factors 



Any scheme for modeling, and hence prediction, of pollen concentration must 

 include the many factors shown in the diagram, in approximately that relationship. 

 There are unanswered questions at many points in this conceptualized model, so 

 that accurate predictions of pollen concentration at any point in space and time 

 will not really be available with any degree of accuracy in the near future. 



Plant Diseases — The 

 supply of the world depends or 

 crops, every one of which is subject to 

 diseases or pest attacks that can and 

 do prejudice entire crops over regions 

 of considerable size. (See, for exam- 

 ple, Figure X-8) For cereal-grain 

 crops, the answer to rust and smut 

 diseases has been to continue to breed 

 resistant strains, each of which has a 

 useful life of one or two decades, until 

 the parasitic organism develops a 

 form that overcomes the resistance of 

 the host. Can this go on indefinitely, 

 especially since populations of wild 

 ancestors of these horticultural species 

 are disappearing? 



For some fungus diseases of crop 

 plants, prevention is exercised by re- 

 stricting culture to certain climates or 

 special soils. In other instances chem- 

 ical inhibitors of fungus growth are 

 administered. Similar measures are 

 used against insect pests and sucking 

 insect vectors of virus diseases. The 

 inocula for these diseases and pest 

 attacks are in most instances carried 

 passively by the atmosphere. But only 

 in a few instances do we know in 

 what quantities, in what directions, 

 and with what survival as viable en- 

 tities the inocula are transported and 

 deposited. The "triangle of epidemiol- 

 ogy" — origin, transport or vectoring, 

 and infection — thus depends heavily 

 on information about atmospheric 

 transport. We could learn much about 

 probabilities for transport of many 

 kinds of organisms through full 

 knowledge of the transport of a few 

 that we can readily collect in transit, 

 identify with certainty, and test re- 

 liably for viability. 



It has been found appropriate for 

 aerobiology, at least in the context of 

 the IBP, to take under its wing certain 

 studies of diseases that are not con- 

 fined to atmospheric transport consid- 

 erations. From an ecological view- 

 point, diseases of crop plants are 

 exaggerations of natural situations be- 

 cause of ecological imbalances intro- 

 duced by agricultural practices such 



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