The isolating effect of greenhouses on arthropod pests : a case-study on Clepsis spectrana (Lepidoptera: Tortricidae) / J. van den BosIntegrated Pest Management in apple orchards in the Netherlands : a solution for selective control of tortricids / R.H. de ReedeOptimal selection and exploitation of hosts in the parasitic wasp Colpoclypeus florus (Hym., Eulophidae) / L.J. Dijkstra