Pea Aphid Outbreaks and Virus Epidemics on Peas in the US Pacific Northwest: Histories, Mysteries, and Challenges

Fig. 4. Twenty-three year history of pea aphid outbreaks and virus epidemics on field peas in the Palouse region of eastern Washington. Values for 1983-1986 were extrapolated from published accounts and personal observations of researchers. For 1987 to 2005, index values of 3 to 4 reflect outbreak-epidemic years (arrows [↓] show all outbreak years).



Image from Plant Health Progress article:
Pea Aphid Outbreaks and Virus Epidemics on Peas in the US Pacific Northwest: Histories, Mysteries, and Challenges