Thresholds and IPM: Still a good idea?

The concept of economic thresholds was introduced by Stern et. al in 1959, in response to the overuse of insecticides such as DDT, toxaphene, parathion, diazinon, etc. Rather than spraying on a calendar basis, as many growers were doing, the authors made the case that insecticide use could be reduced if they were applied only when the density of the insect population reached a threshold level that would result in unacceptable yield and economic losses.

Since that time, the concept…