Investigations on the potential damage caused to cucumber fruit by the polyphagous predatory bug Dicyphus tamaninii Wagner (Heteroptera: Miridae) under different nutritional conditions / Untersuchungen über die potentiellen Saugschäden durch die polyphage räuberische Wanze Dicyphus tamaninii Wagner (Heteroptera: Miridae) an Gurken bei unterschiedlichen Nahrungsangeboten

The present study aimed to investigate the potential damage that the polyphagous predatory bug Dicyphus tamaninii Wagner (Heteroptera: Miridae) might cause to cucumber fruits, under different nutritional conditions. Two sets of experiments were designed, the first set was to study the damage caused to cucumber fruits under different nutritional treatments with (1) cucumber leaves, (2) Aphis gossypii Glover and (3) Ephestia kuehniella Zeller eggs. Another experiment was conducted on predatory females, which were maintained exclusively on either A. gossypii or cucumber leaves for 24 h prior to the experiment. The second set was devoted to investigate the cucumber leaf-fruit preference when the predatory bug was exclusively offered either (1) A. gossypii, (2) cucumber leaves or (3) left starved for 24 hours prior to the experiments. The results of the experiments on the damage to fruits revealed that the number of feeding punctures caused by the predator was significantly reduced by the presence of the leaf, A. gossypii or E. kuehniella eggs. When the predatory females had been fed on A. gossypii as prey for 24 hours prior to the experiments, only an average of 2.2 puncture/day/♀ was recorded. While when they had access to cucumber leaves only, the number was significantly increased to 3.1 puncture/day/♀. Highest number of feeding punctures on cucumber fruit was encountered with the starved individuals, where one D. tamaninii female made in average 4.7 puncture/day. The results of the experiments on the leaf-fruit preference showed that substantial increase in the probability that the predator would be found on leaf or fruit was only noticed after 12 h with the "A. gossypii" treatment, 6 h with the "cucumber leaves" and only after 1 h with the "starved" ones, where they started immediately seeking out the leaves. Moreover, D. tamaninii adults preferred generally leaves to cucumber fruits. The results of the present study lead to the conclusion that the potential damage to cucumber fruits by the phytophagous predator remains low. Das Ziel der vorliegenden Arbeit war es, die möglichen Saugschäden, die durch die Raubwanze Dicyphus tamaninii Wagner (Heteroptera: Miridae) an Gurkenfrüchten bei unterschiedlichen Nahrungs angeboten angerichtet werden können, zu untersuchen. Dazu wurden zwei Versuchsreihen durchgeführt. In der ersten Versuchsreihe sollte ermittelt werden, wie hoch die Schäden für die Gurkenfrüchte bei einem unterschiedlichen Nahrungsangebot von Gurke