MANAGEMENT OF WESTERN FLOWER THRIPS ON CUCUMBER WITH DICYPHUS-TAMANINII (HETEROPTERA, MIRIDAE)

Late instar nymphs of Dicyphus tamaninii Wagner (Heteroptera:Miridae) were released in a 1:10 and a 3:10 ratio of the predator to prey in a high initial infestation of 5 adult thrips per leaf and in a low initi al infestation of 1 adult thrips per leaf in greenhouse cucumbers. The 3:10 D. tamaninii:Frankliniella occidentalis (Pergande) ratio kept th rips populations under the economic injury level. This ratio is recomm ended for controlling the high thrips populations that are common in M editerranean greenhouses, The 1:10 D. tamaninii:fi: occidentalis ratio worked well when thrips populations were low but not when thrips dens ity was high. The efficiency of D. tamaninii in low thrips populations is very interesting for developing IPM programs in which only limited releases of D. tamaninii can be done. Sampling cucumber flowers to ev aluate thrips densities has not been a very effective method because a variable proportion of the thrips population is located in flowers, w hile D. tamaninii is unlikely to be found in flowers. (C) 1996 Academi c Press, Inc.