Disease Incidence Gradient and the Effect of Seedbed Infection on Potato Virus Y Outbreaks in Tobacco. B. A. Latorre, Adjunct Professor, Facultad de Agronomía, Pontificia Universidad Católica, Casilla 114-D, Santiago, Chile. Plant Dis. 67:302-304. Accepted for publication 13 August 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-302.

Veinbanding caused by potato virus Y (PVY) has become widespread in Chilean tobacco, affecting flue-cured, burley, and oriental types. Severe losses have resulted from a necrotic strain of PVY. A disease incidence gradient was determined by regression analysis (log_e I = log_e a – b log_eX) of disease incidence over distance in meters from a line-focus source of weeds growing along irrigation ditches. Results indicated that weeds may be important sources of PVY and/or breeding sites for aphid vectors. Incidence of PVY in tobacco seedlings just before transplanting varied from 1 to 19%; however, final incidence seemed to be highly dependent on other factors, presumably aphid vector activity.

Keyword(s): epidemiology, Nicotiana tabacum.