study of pesticide use on fruit and vegetable crops. Those studies use data from field trials and expert opinion to estimate pest-induced losses crop by crop basis with current pesticide use, without pesticides, and with a 50% reduction in pesticide use. They construct alternative production scenarios for each crop to estimate changes in input use. Current prices are then used to value changes in per-acre production costs and per-acre yield losses, which are added to obtain an estimate of the costs of changes in pesticide use.
Pimentel and associates compile estimates of crop losses due to insects, diseases, and weeds crop by crop. They then add losses due to each class of pest on each crop to obtain estimates of aggregate crop losses in US agriculture. As they acknowledge, this procedure overestimates crop losses because of overlaps in damage caused by insects, diseases, and weeds. Crop losses are valued at current crop prices. One of the more recent of these studies (Pimentel et al. 1991) estimates that aggregate crop losses amounted to 37% of total output in 1986, up from 33% in 1974. Those estimates were compared with USDA assessments for the 1940s and 1950s, which estimated aggregate crop losses due to pests at 34% and 31% respectively, of total output. In comparison, Cramer (1967) estimated crop losses of around 28% due to all pests in all of North and Central America. Pimentel and associates interpret the temporal coincidence of