Management of Western Flower Thrips on Cucumber withDicyphus tamaninii(Heteroptera: Miridae)

Late instar nymphs ofDicyphus tamaniniiWagner (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 initial infestation of 1 adult thrips per leaf in greenhouse cucumbers. The 3:10D. tamaninii:Frankliniella occidentalis(Pergande) ratio kept thrips populations under the economic injury level. This ratio is recommended for controlling the high thrips populations that are common in Mediterranean greenhouses. The 1:10D. tamaninii:F. occidentalisratio worked well when thrips populations were low but not when thrips density was high. The efficiency ofD. tamaniniiin low thrips populations is very interesting for developing IPM programs in which only limited releases ofD. tamaniniican be done. Sampling cucumber flowers to evaluate thrips densities has not been a very effective method because a variable proportion of the thrips population is located in flowers, whileD. tamaniniiis unlikely to be found in flowers.