Purple blotch is most severe in hot humid onion climates. Has not been reported in Chile
1 Known Hosts
Allium cepa
onion
Yes
ALTEPO-5,ALTEPO-6,CABI CPC
Seed as a pathway uncommon. There are only a few reports of Alternaria porri being detected on onion seeds (ALTEPO-1). Gupta and Pathak, 1988 (ALTEPO-6) were not able to show seed contamination by Alternaria porri
Yes
Agar plating
Agar Plating is s standard method of the NSHS
Agar plating (ALTEPO-7)
ALTEPO-5,NSHS USDA
Chemical
Chemical seed treatments and disinfestation methods like hot water are possible but may be phytotoxic; however, newer seed treatment chemicals may be available, so it's advisable to consult with companies supplying these treatments.
Aveling, T. A. S., Snyman, H. G. &Naude, S. P. (1993). EVALUATION OF SEED TREATMENTS FOR REDUCING ALTERNARIA-PORRI AND STEMPHYLIUM-VESICARIUM ON ONION SEED. Plant Disease 77: 1009-1011