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Wis* Nematode Diseases of Potato and Other Crops , (l) Emphasize 



control and possible eradication of pests through soil fumigation; 



(2) learn influence wild and cultivated host plants and soil flora 

 have on its survival, life cycle, and incidence, 



PI. Path. 904 Coop. ARS 



Virus Diseases 



Ark. Studies on Importance. Etiology and Control of Plant Virus 

 Diseases . (1) Learn relative importance of virus diseases in 

 commercial crops in State; (2) obtain information on source of 

 virus infections and their dissemination; (3) initiate work on 

 virus disease control which may be suggested as a result of 

 information obtained from studies. 

 PI. Path. 445 



Calif. Insect Vectors of Plant Viruses , (l) Correlate economic 



losses resulting from aster yellows with distribution of strains 

 of virus in the State; isolate strains and learn host ranges and 

 vector relationships; (2) maintain cross protection tests with 

 strains collected to learn degree of protection occurring in host 

 plants and leaf hopper vectors; (3) compare incubation periods and 

 retention patterns of virus strains in different species of leaf- 

 hoppers following controlled acquisition feeding period of varying 

 lengths; (4) study transmission of viruses by aphids, beetles, and 

 leaf hoppers; (5) compare host ranges and symptoms induced by viruses. 

 Ent. & Parasitol. 657 



Calif. Studies on the Nature of Viruses. A. Mode of Virus Multi- 

 plication. B. Morphological Classification of Virus. C. Biochemical 

 Studies on Viruses . (1) Learn manner in which infectious nucleic 

 acid multiplies and moves in plant; (2) set up a natural classification 

 system for plant viruses based o.i morphology and serology of viruses; 



(3) gain an understanding of biochemical changes occurring in virus- 

 infected plants, to devise quick tests to learn virus infections, and 

 to develop chemotherapeutants for control of plant virus diseases. 



PI. Path. 1334 Coop. FES 



Calif. Aphids as Vectors of Field Crop Virus Diseases . Learn and clarify 

 the vector-virus-host plant relationships existing among the aphid- 

 borne virus diseases of various crop plants. 

 Ent. & Parasitol. 1365 A 



