Aphid outbreaks
The graph shows the occurrence of aphid outbreaks in the Palouse since 1983. The index is generated by sampling approximately 10 pea fields throughout the region at intervals during the first part of the growing season.
Aphid outbreaks
Clement and Eigenbrode in review
Click on image to view larger version
For this index, a value of 0 approaching 1 = aphids absent or ‘few’ counted on plants; 1 approaching 2 = high counts (peak averages of 10–99 aphids per plant) in 26–50% of the sampled fields; 2 approaching 3 = very high counts (peak averages >100 aphids per plant) in 51–75% of the fields; and 3 approaching 4 = peak counts averaging >100 aphids per plant in 76–100% of the fields (Clement, in press). The very high aphid densities that characterize index values 3–4 represent outbreaks.