ESTIMATION OF PEA YIELD LOSS FROM SEVERE ROOT ROT AND DROUGHT STRESS USING AERIAL PHOTOGRAPHS AND A LOSS CONVERSION FACTOR

Vertical aerial photographs were taken over commercial pea (Pisum sativum L.) fields in the Picton-Wellington region, Ontario, in 1975 (a drought year) and in 1976 (a non-drought year) using Kodak Aerochrome Infrared film 2443. Optical separations into black and white images were necessary to assist in delineating healthy crop boundaries from severe root rot- and drought-affected areas (37.14%) as well as void areas (5.29%) from 1975 photographs of 12 selected fields. In these fields, excluding the void areas, an estimated yield loss of 22.7% was calculated by multiplying the percentage of the affected area by an average yield loss conversion factor of 0.61 derived from all available data from greenhouse- and field-grown plants of several commercial pea cultivars.