Abstract
Two treatments to control the olive pest Prays oleae Bern. were compared in a 2-year study at five different olive-growing sites. In one treatment the pesticide dimethoate was sprayed, and in the second treatment ethylene was applied to olive trees in the form of ethrel (2-chloroethyl-phosphonic acid). In 2005 and 2006 the ethylene treatment provided a mean benefit of 340 Euros per hectare, whereas in the dimethoate treatment there were losses of 100 Euros per hectare. We conclude that treatments with dimethoate, the most widely used pesticide in southern Spain, are undesirable, reducing both the activity and killing efficiency of indigenous predators of P. oleae, mainly the green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), compared to control and ethylene-treated trees.