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 initial infestation of 1 adult thrips per leaf in greenhouse cucumbers. The 3:10 D. 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 1:10 D. tamaninii:fi: occidentalis ratio worked well when thrips populations were low but not when thrips density 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 evaluate thrips densities has not been a very effective method because a variable proportion of the thrips population is located in flowers, while D. tamaninii is unlikely to be found in flowers. (C) 1996 Academic Press, Inc.